Why? Let me count the ways. You can never count on any Seebeck voltage to be immediately offset, there are far too many variables. Best example I can think of...why is there an Ohms Offset Compensation feature on any good high resolution DMM. 1) Try measuring a 1 or 10 Ohm resistor with your 3458A in 4-wire mode using inexpensive nickel-plated leads and even allow plenty of time for everything to thermally stabilize. Using Ohms Offset Compensation, enable and disable it and observe the difference. If the Seebeck voltages were all immediately offset, as you say, there would be no difference. But there most certainly is. Or simply, why is there a need for ohms offset compensation feature if all Seebeck voltages cancel each other out. Sure, nickel-plated is a horrible choice but if it all canceled, what difference would it make how bad is. 2) The cal lab workhorse calibrator is the 5700A/5720A. In between trips back to Fluke for full calibration, there is an interim external calibration procedure using the 732B, 742A-1 & 742A-10k. If someone used a set of gold-plated interconnects for this procedure, they would be laughed out of the lab and the calibrator would be useless until recalibrated properly. A set of 5440A-7002 (banana plug) cables comes with this calibrator (5440A-7003 spade lugs for 5720A) and recommended for the calibration procedure but other Beryllium Copper or pure Copper cables are also acceptable. 3) Lab air drafts will never allow true thermal symmetry around the DMM or DUT terminals. To convince yourself, place an oscillating fan several feet back from the DMM and DUT terminals and using the 1 or 10 Ohm setup from above, again with the nickel-plated leads, watch the variations. Sure the fan and the nickel-plated exaggerates the issue but it quickly dispels the notion that all the Seebeck voltages are canceled out. BTW, the plating layer temperature on a plated terminal will be somewhere between the temperature of the base metal and mating terminal it's connected to. This is not just theory, my 40+ years in the cal lab is driving my arguments but it never hurts to have physical-science on your side. Don Johnson -----Original Message----- From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Mike S Sent: Monday, August 25, 2014 11:03 AM To: volt-nuts@febo.com Subject: Re: [volt-nuts] 732A and Prologix received On 8/25/2014 11:02 AM, Don@True-Cal wrote: > Silver or Gold plating on the terminal or wire will introduce the > undesirable dissimilar metal properties, both at the plating junction > and at the plating metal to DUT terminal. Why? Any Seebeck effect is immediately offset in the opposite direction, since both junctions are (under normal conditions) at essentially the same temperature (e.g. there's a copper-gold thermocouple, the minimal thermal resistance of a micron of gold on the contact(s), then a gold-copper thermocouple). It seems to me that the improved consistency of the contact outweighs any loss from the thermocouples. A more typical contact would be copper-nickel plate-gold plate, but the concept is the same. Unless there is heat flowing through the entire assembly so one thermocouple is warmer than the offsetting one (e.g. shortly after plugging in a banana plug warmed by body heat), they simply cancel. Even if connecting gold plated to nickel plated contacts, it works out the same - a copper-nickel-gold-nickel-copper connection is completely offset. It's when the offsetting thermocouples occur across a temperature gradient that you have problems. -- Mike _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

On 8/25/2014 9:54 PM, Don@True-Cal wrote: > Why? > > Let me count the ways.You can never count on any Seebeck voltage to > be immediately offset, there are far too many variables. ... > A set of > 5440A-7002 (banana plug) cables comes with this calibrator > (5440A-7003 spade lugs for 5720A) For those leads, Fluke says they have the advantage of "minimizing the emf caused by temperature difference between the ends of the leads." I don't have much argument with that - if there's a temperature difference between the ends, you won't have an equal thermocouple offset, so minimizing such effects makes sense. But, since those leads use pure copper wiring ("Belden 8262 or 8719 or equivalent"), how does having only the contact itself made of tellurium copper (TC) make a difference? Shouldn't they be TC end-to-end, with gas tight crimped connections? Does the tinning on that copper cable have an effect? What's the Seebeck coefficient for a copper to tellurium copper connection? You said that "Tellurium Copper is usually not used for a device's terminal posts but used as the lead wire..." But, Fluke does exactly the opposite - those Fluke leads use TC connectors and are characterized "while engaged in a five-way binding post of Tellurium Copper Alloy 145, half hard." Since they use pure copper cabling, I'd think they'd work even better with a pure copper binding post, since the offsetting thermocouples would be in close proximity, and not at different ends of the cable. You earlier said "Any type of Silver or Gold plating on the terminal or wire will introduce the undesirable dissimilar metal properties, both at the plating junction and at the plating metal to DUT terminal." Now you emphasize that by saying "If someone used a set of gold-plated interconnects for this procedure, they would be laughed out of the lab and the calibrator would be useless until recalibrated properly..." But, the specs for the Fluke 5440A-7003 which you say are appropriate for the 5720A state: "Connector materials: Copper space lug with gold plating over silver plating." (Both platings!!) Is someone to be laughed out of the lab for using the cables they're supposed to use? The 5440A-7002 specs aren't clear, but if they're not plated, are you required to clean them of copper oxide for every use? It seems that would be necessary, since a gold-copper thermocouple is ~0.5 uV/C, while a copper-copper oxide one is ~1000 uV/C. You seem to be stating one thing, but then giving evidence which contradicts your claim. It seems that Fluke uses TC where there's thermal mass, and pure copper where there's little, and uses plating in addition. Please clarify, this isn't making sense to me.

 The MATH function is accessible from the keypad.  I don't have an IEEE

 I have made my own "low thermal" measurement leads from Pomona #4892

 I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have

 Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all

 Since the 1.018 and 1.0 volt outputs are passive and derived from

 Sorry for the long dissertation.  Friends get mad at me for being so

 I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit

 When you remove and work on the battery pack always have the AC

 The "CAL" light is to indicate that power has not been lost to the

 What type of hookup leads are you using when measuring the 1 volt

 I hope all of this helps.

Is there any way to tell when the function key routine is complete? In the case of taking multiple readings using the DEFKEY and MATH function, I don't see any indication when the routine is complete. In one particular case, I am taking a 100 readings with NLPC set for 1000 so its a long while before it's complete, but i have to guess when it's done. Thanks, Randy On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans <randyevans2688@gmail.com> wrote: > Bill, > > I am trying to figure out the MATH function without much success. I input > the sequence you said (I looked up the instructions to understand what you > did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and > it shows up on the display when I input BLUE F1. I hit ENTER and it takes > the 40 measurements and the MATH symbol shows on the display during the > measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I > get a MATH ERR symbol on the display. I tried it a couple of times and the > same result so I am doing something wrong. Is there a better source for > explaining how to do front panel masurements than the User Guide, which > seems oriented at programming automatic rather than manual measurements. > > Randy > > > > On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold <wpgold3637@att.net> wrote: > >> Randy: >> >> The MATH function is accessible from the keypad. I don't have an IEEE >> interface right now that works. You can also program the numeric keypad >> keys to have preprogrammed functions. DEFKEY >> >> I have made my own "low thermal" measurement leads from Pomona #4892 >> banana plugs and Belden #9272 wire. Why 9272, because it was handy at the >> time. It is tin plated copper, shielded twisted pair 20 ga. I have plans >> to do custom cables with 16 ga. bare copper wire that I will twist and >> then >> put a braided shield over it. I simply cannot find what I want so I will >> build my own cable. I have done something like this before and it worked >> fine. When I get a "round toit". >> >> I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have >> used >> in the past to verify my homemade "low thermal" leads as described above. >> Frankly I cannot see any difference between using the 1756 cables and my >> homemade cables once I give them a few minutes for the thermals to go >> away. >> As far as I can tell and measure the differences, if any, are below 0.1 >> ppm >> at 10 volts. >> >> Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all >> adjustable you may be seeing a misadjusted 1 volt from the 732A. As far >> as >> the instability of the readings it is hard to determine which is causing >> the >> problem. I have programed (DEFKEY) a numeric keypad key #1 with the >> following code. "MATH 14;NRDGS 40;TRIG 4;TRIG ;" So what this does is >> set >> the MATH to "Statistics" (store high reading/low reading/ and mean of the >> readings) in the registers, the number of readings to "40", the trigger to >> "hold" (which keeps the meter from triggering until I press "ENTER" and >> then >> trigger the sequence of 40 readings when I push the "ENTER" button. You >> can >> do all of this manually from the keypads but since I use this sequence a >> lot >> I have preprogrammed it. This is after I set digits to "8" and PLC to >> 100. >> Once those 40 readings are finished then you can access the various MATH >> statistic registers, using the menu, by entering "MATH" and then a 2 for >> low, a 4 for mean, and 13 for high. Of course you could do all of this >> through the IEEE also. The 3458A has a very rich set of measurement >> commands. I am still learning all of them. It depends upon what I am >> trying to accomplish. >> >> Since the 1.018 and 1.0 volt outputs are passive and derived from >> resistive dividers from the 10 volt, I don't see how they could contribute >> to the varying readings you are measuring. I think I would put a short on >> the input of the 3458A and manually set the range to 1 volt and then >> observe >> the variations that way without the 732A involved. When I do this I see a >> variation from low reading to high reading of 0.125 uVolts and then >> another >> 40 I get 0.155 uVolts. This is without the GUARD connected to the low >> side >> of the measurment terminals, GUARD connected doesn't seem to affect the >> readings. So that is the base noise of the 3458A without the 732A, >> somewhere below .2uVolts. When hooked up to the 732A 1.0 volt output I >> got >> a variation of 0.159 uVolts using the same 40 reading method above. I >> would >> use this to determine where your problem might exist. Just having the >> meter >> input shorted will point you in the right direction. Meter, cables or >> 732A. >> >> Sorry for the long dissertation. Friends get mad at me for being so >> detailed sometimes. >> >> Bill >> >> ----- Original Message ----- >> From: "Randy Evans" <randyevans2688@gmail.com> >> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> >> Sent: Sunday, August 24, 2014 7:22 AM >> Subject: Re: [volt-nuts] 732A and Prologix received >> >> >> > Bill, >> > >> > I have convinced myself that the problem I an seeing is due to thermals. >> > If I move the cables (with gold-plated banana plugs) using a small >> towel >> > rather than letting my hand touch the plugs, it is much more stable. >> If I >> > then hold the banana plug with my hand after the reading has stabilized, >> > the reading drifts rapidly upward. I am trying to check the stability >> of >> > the reading but I haven't figured out the MATH function yet. I assume >> this >> > is a programmed function using GPIB only? >> > >> > The stability I am seeing by manually recording readings (using NLPC of >> 100 >> > and 1000) is much greater than what you are measuring on your system. >> Not >> > sure how to ascertain if it's the 3458A or the 732. The value of the >> > readings are very different between the two - the 3458 reads about 50 uV >> > high on the 10 V output and about 12 uV low on the 1V output. Rather >> large >> > differences (this is after an ACAL). I need to find some better cables >> to >> > make sure the errors are not due to thermals again. >> > >> > Randy >> > >> > >> > On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold <wpgold3637@att.net> wrote: >> > >> > > Randy: >> > > >> > > I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit >> > > perfect. Power Sonic PS-640, Genesis NP4-6, Panasonic LC-R064R5C and >> > > others >> > > that are in this size and package. Order from one of the usual >> electronics >> > > distributors like Allied, Mouser, Digikey. This is a very common >> battery >> > > as >> > > it is used in a lot of "EXIT" signs so they are lighted when the power >> goes >> > > out. I don't see how the 12V 7AH will fit as they are too large. I >> guess >> > > you could use a 12V 5AH (PS1250) as it is the same size as 2 x 6 volt >> 4 >> AH >> > > but the terminals are in the wrong place so you will have to "nibble" >> out >> > > the aluminum plate that holds them in the 732A battery pack. You have >> to >> > > be >> > > careful if you use the 12v 5AH as you will have 4 extra battery >> connection >> > > leads to deal with and connect correctly. I would stick with the 6V >> 4AH. >> > > New batteries will last around 12 to 14 hours before the "CAL" light >> goes >> > > out when AC power is not applied. So shipping to Cal Lab can be a >> problem >> > > if it is a distance away, or you have to use a shipper like UPS or >> FEDEX >> > > and >> > > you ship the night before and then use their "Morning delivery" and >> the >> Cal >> > > Lab is expecting your 732A. Same on the way back to you. Of course >> you >> > > could always strap another battery on the 732A and hook it up to the >> "ext >> > > power" plug to last longer. I have seen it done. The issue is to get >> the >> > > Cal Lab to charge the extra battery before they ship the 732A back to >> you. >> > > >> > > When you remove and work on the battery pack always have the AC >> power >> > > plugged in. The "CAL" led will stay on because the 18.6 v regulated >> supply >> > > is working. >> > > >> > > The "CAL" light is to indicate that power has not been lost to the >> > > Reference Amp or other associated circuits. When the raw supply >> (battery) >> > > voltage drops below about 21 volts the "CAL" light will go out. Below >> that >> > > voltage the heater circuits will not work correctly and the 18.6 volt >> > > regulated supply will not regulate. The requirement is that the >> Reference >> > > Amp be kept "alive" at all times to maintain the output voltage that >> was >> > > measured at the time of the most recent Calibration or Certification. >> When >> > > the semiconductor junctions are unbiased and cool off when power is >> lost, >> > > and then power is restored the result will be a different 10 volts >> than >> > > before the power failure. My experience is that after all of the >> years >> > > that >> > > these units have been powered up, this won't happen and when power is >> lost >> > > and then restored, even months later, the 732A will come back to >> almost >> > > exactly the same 10 volts as when they lost power, usually with in 0.2 >> PPM >> > > after 24 hours of "warm up". >> > > >> > > What type of hookup leads are you using when measuring the 1 volt >> > > output? What is the PLC set to? I always use 100 PLC to measure >> this. >> If >> > > you don't have "low thermal" connection leads you can experience uV >> changes >> > > for a minute or more after plugging in the leads due to the "thermals" >> > > generated because of the difference in temperature between the banana >> jacks >> > > on the 732A and the banana plugs of the leads. I have found that even >> just >> > > plugging in the lead will generate a thermal difference because of >> > > difference of temps and some heating due to the physical act of just >> > > inserting the plug because of friction between the jack and plug (my >> theory >> > > at any rate). You have to allow at least a minute or more before >> being >> > > able >> > > to make a measurement after plugging in the leads. I just measured >> the >> > > variation of the 1 volt output of my 732A and using my 3458A and I >> got a >> > > total difference of 0.159 uV over 40 measurements using 100 PLC on >> the >> 1 >> > > volt range of the 3458A. Using the MATH function and all of the data >> you >> > > can collect. That was after waiting for several minutes after >> plugging >> in >> > > the leads. >> > > >> > > I hope all of this helps. >> > > >> > > Bill >> > > >> > > >> > > >> > > ----- Original Message ----- >> > > From: "Randy Evans" <randyevans2688@gmail.com> >> > > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> >> > > Sent: Friday, August 22, 2014 9:03 PM >> > > Subject: Re: [volt-nuts] 732A and Prologix received >> > > >> > > >> > > > Todd, >> > > > >> > > > Thanks for the info. I have several Panasonic 12V 7 AH batteries >> that >> I >> > > > keep topped off and they have very low current draw (~2 to 3 mA at >> 13.5 >> > > > VDC) when charged and at their float voltage, so I am pretty sure >> they >> > > are >> > > > in good condition. I will look at getting those in the units after >> I >> > > > ascertain the condition of the 732. >> > > > >> > > > So now I have a what appears to be a functioning 3458A and a 732A >> but >> > > they >> > > > slightly disagree. I am like the man with two watches that disagree >> on >> > > the >> > > > time - which is correct? For the moment, i am only concerned with >> > > > stability. The need for absolute accuracy will come later. >> > > > >> > > > Randy >> > > > >> > > > >> > > > On Fri, Aug 22, 2014 at 8:06 PM, Todd Micallef <tmicallef@gmail.com >> > >> > > wrote: >> > > > >> > > > > Randy, >> > > > > >> > > > > You have two possible choices. It can be configured with 4 x 6v >> 4Ah >> > > > > batteries or 2 x 12v 7Ah batteries. Hopefully the previous owner >> has >> > > > > modified the battery pack already. A couple of mine needed a >> nibbler >> > > tool >> > > > > to remove enough of the aluminum cover that fits over the tops of >> the >> > > > > batteries. The original cover will short out to the battery tabs >> > > regardless >> > > > > of the battery configuration if this is not done. >> > > > > >> > > > > You can find larger capacity batteries that will give you slightly >> more >> > > > > battery life. I lost a couple sets of mail-order batteries after a >> few >> > > > > extended outages. I would recommend going with locally bought >> batteries >> > > > > instead of the cheaper mail order. My local Batteries Plus will >> > > typically >> > > > > have some warranty if I remember correctly. Moving forward I will >> only >> > > use >> > > > > 2 12v batteries and pre-charge them on a battery charger to >> equalize >> > > them >> > > > > before putting them in the 732A. I think the cheap batteries did >> not >> > > > > discharge equally, and would not recover when power was applied. >> > > > > >> > > > > Inspect the back plane for damaged traces and look at the >> capacitors. I >> > > had >> > > > > a few that looked questionable. So far, I have replaced all the >> big >> > > caps >> > > on >> > > > > the pre-regulator and regulator boards. My feeling is that once >> these >> > > go >> > > > > online, they should run as long as possible between repairs. >> > > > > >> > > > > The battery charger circuit may need adjusting. I tweaked mine and >> it >> > > > > seemed to work fine. >> > > > > >> > > > > Todd >> > > > > >> > > > > >> > > > > On Fri, Aug 22, 2014 at 10:42 PM, Randy Evans < >> > > randyevans2688@gmail.com> >> > > > > wrote: >> > > > > >> > > > > > I received my Fluke 732A today. Just powered it up but it needs >> new >> > > > > > batteries. Any suggestions for sources (I haven't opened up the >> unit >> > > > > yet - >> > > > > > I want to make sure it works before doing that). Also received >> the >> > > > > > ProLogix USB-GPIB adapter. I plan on using Mark Sims' CAL ran >> data >> > > > > dumper >> > > > > > program to get the CAL data from my 3458A. Should be a busy >> weekend. >> > > > > > >> > > > > > Randy >> > > > > > _______________________________________________ >> > > > > > volt-nuts mailing list -- volt-nuts@febo.com >> > > > > > To unsubscribe, go to >> > > > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> > > > > > and follow the instructions there. >> > > > > > >> > > > > _______________________________________________ >> > > > > volt-nuts mailing list -- volt-nuts@febo.com >> > > > > To unsubscribe, go to >> > > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> > > > > and follow the instructions there. >> > > > > >> > > > _______________________________________________ >> > > > volt-nuts mailing list -- volt-nuts@febo.com >> > > > To unsubscribe, go to >> > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> > > > and follow the instructions there. >> > > >> > > _______________________________________________ >> > > volt-nuts mailing list -- volt-nuts@febo.com >> > > To unsubscribe, go to >> > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> > > and follow the instructions there. >> > > >> > _______________________________________________ >> > volt-nuts mailing list -- volt-nuts@febo.com >> > To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> > and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> > >

My post on this thread earlier today seems to be lost (maybe the system change) so I am re-posting some of it (corrected) since it's apropos to the discussion. Anyone who has calibrated (CAL 0 anyway) a 3458A has enough information to deduce that lowest input short voltage is going to be a copper wire since the meter is set to zero volts during calibration using a heavy gauge (14 to 16) copper wire. This is very convenient since it is so easy to duplicate in the field and makes simple inexpensive test leads best for high precision measurements. In order for the 3458A to make full accuracy measurements (8 digit) NPLC must be set to 1000 (according to the User's Guide). If you use a lower NPLC value there is a table in the User's Guide that can be used to determine how accurate your measurements are going to be. Just for fun I ran several shorts for NPLC 1000 on my 3458A. It has been about a year since I clid my last CAL 0 so it was going to be interesting at least for me. The first shunt was my test "U' shaped shunt that I used for my last CAL 0. Note: STP = Shielded Twisted Pair. Calibration shunt -0.00021mv ± 10nV Equilibration time 5 minutes. 14 gauge per Calibration Manual. "U" heavy wire -0.00021mv ± 10nV Equil. time 5 minutes. Used the through holes in the Input banana posts only. Copper wire -0.00019mv ± 10nV NAPA PVC covered automobile wire at same contact points as CAL shunt Standard Ground Plate -0.00040mv ± 10nV Equil. time 5 minutes. Gold plated ground plate from my Datron 4910 Copper wire -0.00019mv ± 10nv Equil. time 2 seconds. Used the banana through holes. STP 2 meter test lead -0.00021mv ± 10nV Equil. time 2 seconds. M27500 24 gauge STP Tefzel insulation. Banana plugs -0.00021mv ± 30nV Equil. time 20 minutes. My best "Perfect" gold plated plugs with copper wire. Note that all my test shorts equilibrate to virtualy zero volts. There is almost no Seebeck voltage for any of my test shorts as long as the system is allowed to equilibrate. Equilibation times varied between less than 2 seconds up 20 minutes with longer times due to excessive thermal mass. Excessive thermal mass also caused some voltage instability. Charlie On 8/25/2014 6:54 PM, Don@True-Cal wrote: > Why? > > Let me count the ways. You can never count on any Seebeck voltage to be immediately offset, there are far too many variables. Best example I can think of...why is there an Ohms Offset Compensation feature on any good high resolution DMM. 1) Try measuring a 1 or 10 Ohm resistor with your 3458A in 4-wire mode using inexpensive nickel-plated leads and even allow plenty of time for everything to thermally stabilize. Using Ohms Offset Compensation, enable and disable it and observe the difference. If the Seebeck voltages were all immediately offset, as you say, there would be no difference. But there most certainly is. Or simply, why is there a need for ohms offset compensation feature if all Seebeck voltages cancel each other out. Sure, nickel-plated is a horrible choice but if it all canceled, what difference would it make how bad is. 2) The cal lab workhorse calibrator is the 5700A/5720A. In between trips back to Fluke for full calibration, there is an interim external calibration procedure using the 732B, 742A-1 & 742A-10k. If someone used a set of gold-plated interconnects for this procedure, they would be laughed out of the lab and the calibrator would be useless until recalibrated properly. A set of 5440A-7002 (banana plug) cables comes with this calibrator (5440A-7003 spade lugs for 5720A) and recommended for the calibration procedure but other Beryllium Copper or pure Copper cables are also acceptable. 3) Lab air drafts will never allow true thermal symmetry around the DMM or DUT terminals. To convince yourself, place an oscillating fan several feet back from the DMM and DUT terminals and using the 1 or 10 Ohm setup from above, again with the nickel-plated leads, watch the variations. Sure the fan and the nickel-plated exaggerates the issue but it quickly dispels the notion that all the Seebeck voltages are canceled out. > > BTW, the plating layer temperature on a plated terminal will be somewhere between the temperature of the base metal and mating terminal it's connected to. > > This is not just theory, my 40+ years in the cal lab is driving my arguments but it never hurts to have physical-science on your side. > > Don Johnson > > -----Original Message----- > From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Mike S > Sent: Monday, August 25, 2014 11:03 AM > To: volt-nuts@febo.com > Subject: Re: [volt-nuts] 732A and Prologix received > > On 8/25/2014 11:02 AM, Don@True-Cal wrote: >> Silver or Gold plating on the terminal or wire will introduce the >> undesirable dissimilar metal properties, both at the plating junction >> and at the plating metal to DUT terminal. > Why? > > Any Seebeck effect is immediately offset in the opposite direction, since both junctions are (under normal conditions) at essentially the same temperature (e.g. there's a copper-gold thermocouple, the minimal thermal resistance of a micron of gold on the contact(s), then a gold-copper thermocouple). It seems to me that the improved consistency of the contact outweighs any loss from the thermocouples. > > A more typical contact would be copper-nickel plate-gold plate, but the concept is the same. Unless there is heat flowing through the entire assembly so one thermocouple is warmer than the offsetting one (e.g. > shortly after plugging in a banana plug warmed by body heat), they simply cancel. > > Even if connecting gold plated to nickel plated contacts, it works out the same - a copper-nickel-gold-nickel-copper connection is completely offset. It's when the offsetting thermocouples occur across a temperature gradient that you have problems. > > -- > Mike > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > >

 The MATH function is accessible from the keypad.  I don't have an

 I have made my own "low thermal" measurement leads from Pomona

 I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have

 Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are

 Since the 1.018 and 1.0 volt outputs are passive and derived from

 Sorry for the long dissertation.  Friends get mad at me for being

 I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will

 When you remove and work on the battery pack always have the AC

 The "CAL" light is to indicate that power has not been lost to

 What type of hookup leads are you using when measuring the 1

 I hope all of this helps.

Not that I know of. Just wait and when you don't see a "SMPL" on the display it is done. But then with 1000 PLC that is around 16.66 seconds per reading times 100 readings is somewhere around 28 minutes and there is probably some overhead time so around 30 minutes. Not from the front panel at any rate. Bill ----- Original Message ----- From: "Randy Evans" <randyevans2688@gmail.com> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Monday, August 25, 2014 9:23 PM Subject: Re: [volt-nuts] 732A and Prologix received > Is there any way to tell when the function key routine is complete? In the > case of taking multiple readings using the DEFKEY and MATH function, I > don't see any indication when the routine is complete. In one particular > case, I am taking a 100 readings with NLPC set for 1000 so its a long while > before it's complete, but i have to guess when it's done. > > Thanks, > > Randy > > > On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans <randyevans2688@gmail.com> > wrote: > > > Bill, > > > > I am trying to figure out the MATH function without much success. I input > > the sequence you said (I looked up the instructions to understand what you > > did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and > > it shows up on the display when I input BLUE F1. I hit ENTER and it takes > > the 40 measurements and the MATH symbol shows on the display during the > > measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I > > get a MATH ERR symbol on the display. I tried it a couple of times and the > > same result so I am doing something wrong. Is there a better source for > > explaining how to do front panel masurements than the User Guide, which > > seems oriented at programming automatic rather than manual measurements. > > > > Randy > > > > > > > > On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold <wpgold3637@att.net> wrote: > > > >> Randy: > >> > >> The MATH function is accessible from the keypad. I don't have an IEEE > >> interface right now that works. You can also program the numeric keypad > >> keys to have preprogrammed functions. DEFKEY > >> > >> I have made my own "low thermal" measurement leads from Pomona #4892 > >> banana plugs and Belden #9272 wire. Why 9272, because it was handy at the > >> time. It is tin plated copper, shielded twisted pair 20 ga. I have plans > >> to do custom cables with 16 ga. bare copper wire that I will twist and > >> then > >> put a braided shield over it. I simply cannot find what I want so I will > >> build my own cable. I have done something like this before and it worked > >> fine. When I get a "round toit". > >> > >> I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have > >> used > >> in the past to verify my homemade "low thermal" leads as described above. > >> Frankly I cannot see any difference between using the 1756 cables and my > >> homemade cables once I give them a few minutes for the thermals to go > >> away. > >> As far as I can tell and measure the differences, if any, are below 0.1 > >> ppm > >> at 10 volts. > >> > >> Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all > >> adjustable you may be seeing a misadjusted 1 volt from the 732A. As far > >> as > >> the instability of the readings it is hard to determine which is causing > >> the > >> problem. I have programed (DEFKEY) a numeric keypad key #1 with the > >> following code. "MATH 14;NRDGS 40;TRIG 4;TRIG ;" So what this does is > >> set > >> the MATH to "Statistics" (store high reading/low reading/ and mean of the > >> readings) in the registers, the number of readings to "40", the trigger to > >> "hold" (which keeps the meter from triggering until I press "ENTER" and > >> then > >> trigger the sequence of 40 readings when I push the "ENTER" button. You > >> can > >> do all of this manually from the keypads but since I use this sequence a > >> lot > >> I have preprogrammed it. This is after I set digits to "8" and PLC to > >> 100. > >> Once those 40 readings are finished then you can access the various MATH > >> statistic registers, using the menu, by entering "MATH" and then a 2 for > >> low, a 4 for mean, and 13 for high. Of course you could do all of this > >> through the IEEE also. The 3458A has a very rich set of measurement > >> commands. I am still learning all of them. It depends upon what I am > >> trying to accomplish. > >> > >> Since the 1.018 and 1.0 volt outputs are passive and derived from > >> resistive dividers from the 10 volt, I don't see how they could contribute > >> to the varying readings you are measuring. I think I would put a short on > >> the input of the 3458A and manually set the range to 1 volt and then > >> observe > >> the variations that way without the 732A involved. When I do this I see a > >> variation from low reading to high reading of 0.125 uVolts and then > >> another > >> 40 I get 0.155 uVolts. This is without the GUARD connected to the low > >> side > >> of the measurment terminals, GUARD connected doesn't seem to affect the > >> readings. So that is the base noise of the 3458A without the 732A, > >> somewhere below .2uVolts. When hooked up to the 732A 1.0 volt output I > >> got > >> a variation of 0.159 uVolts using the same 40 reading method above. I > >> would > >> use this to determine where your problem might exist. Just having the > >> meter > >> input shorted will point you in the right direction. Meter, cables or > >> 732A. > >> > >> Sorry for the long dissertation. Friends get mad at me for being so > >> detailed sometimes. > >> > >> Bill > >> > >> ----- Original Message ----- > >> From: "Randy Evans" <randyevans2688@gmail.com> > >> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > >> Sent: Sunday, August 24, 2014 7:22 AM > >> Subject: Re: [volt-nuts] 732A and Prologix received > >> > >> > >> > Bill, > >> > > >> > I have convinced myself that the problem I an seeing is due to thermals. > >> > If I move the cables (with gold-plated banana plugs) using a small > >> towel > >> > rather than letting my hand touch the plugs, it is much more stable. > >> If I > >> > then hold the banana plug with my hand after the reading has stabilized, > >> > the reading drifts rapidly upward. I am trying to check the stability > >> of > >> > the reading but I haven't figured out the MATH function yet. I assume > >> this > >> > is a programmed function using GPIB only? > >> > > >> > The stability I am seeing by manually recording readings (using NLPC of > >> 100 > >> > and 1000) is much greater than what you are measuring on your system. > >> Not > >> > sure how to ascertain if it's the 3458A or the 732. The value of the > >> > readings are very different between the two - the 3458 reads about 50 uV > >> > high on the 10 V output and about 12 uV low on the 1V output. Rather > >> large > >> > differences (this is after an ACAL). I need to find some better cables > >> to > >> > make sure the errors are not due to thermals again. > >> > > >> > Randy > >> > > >> > > >> > On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold <wpgold3637@att.net> wrote: > >> > > >> > > Randy: > >> > > > >> > > I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit > >> > > perfect. Power Sonic PS-640, Genesis NP4-6, Panasonic LC-R064R5C and > >> > > others > >> > > that are in this size and package. Order from one of the usual > >> electronics > >> > > distributors like Allied, Mouser, Digikey. This is a very common > >> battery > >> > > as > >> > > it is used in a lot of "EXIT" signs so they are lighted when the power > >> goes > >> > > out. I don't see how the 12V 7AH will fit as they are too large. I > >> guess > >> > > you could use a 12V 5AH (PS1250) as it is the same size as 2 x 6 volt > >> 4 > >> AH > >> > > but the terminals are in the wrong place so you will have to "nibble" > >> out > >> > > the aluminum plate that holds them in the 732A battery pack. You have > >> to > >> > > be > >> > > careful if you use the 12v 5AH as you will have 4 extra battery > >> connection > >> > > leads to deal with and connect correctly. I would stick with the 6V > >> 4AH. > >> > > New batteries will last around 12 to 14 hours before the "CAL" light > >> goes > >> > > out when AC power is not applied. So shipping to Cal Lab can be a > >> problem > >> > > if it is a distance away, or you have to use a shipper like UPS or > >> FEDEX > >> > > and > >> > > you ship the night before and then use their "Morning delivery" and > >> the > >> Cal > >> > > Lab is expecting your 732A. Same on the way back to you. Of course > >> you > >> > > could always strap another battery on the 732A and hook it up to the > >> "ext > >> > > power" plug to last longer. I have seen it done. The issue is to get > >> the > >> > > Cal Lab to charge the extra battery before they ship the 732A back to > >> you. > >> > > > >> > > When you remove and work on the battery pack always have the AC > >> power > >> > > plugged in. The "CAL" led will stay on because the 18.6 v regulated > >> supply > >> > > is working. > >> > > > >> > > The "CAL" light is to indicate that power has not been lost to the > >> > > Reference Amp or other associated circuits. When the raw supply > >> (battery) > >> > > voltage drops below about 21 volts the "CAL" light will go out. Below > >> that > >> > > voltage the heater circuits will not work correctly and the 18.6 volt > >> > > regulated supply will not regulate. The requirement is that the > >> Reference > >> > > Amp be kept "alive" at all times to maintain the output voltage that > >> was > >> > > measured at the time of the most recent Calibration or Certification. > >> When > >> > > the semiconductor junctions are unbiased and cool off when power is > >> lost, > >> > > and then power is restored the result will be a different 10 volts > >> than > >> > > before the power failure. My experience is that after all of the > >> years > >> > > that > >> > > these units have been powered up, this won't happen and when power is > >> lost > >> > > and then restored, even months later, the 732A will come back to > >> almost > >> > > exactly the same 10 volts as when they lost power, usually with in 0.2 > >> PPM > >> > > after 24 hours of "warm up". > >> > > > >> > > What type of hookup leads are you using when measuring the 1 volt > >> > > output? What is the PLC set to? I always use 100 PLC to measure > >> this. > >> If > >> > > you don't have "low thermal" connection leads you can experience uV > >> changes > >> > > for a minute or more after plugging in the leads due to the "thermals" > >> > > generated because of the difference in temperature between the banana > >> jacks > >> > > on the 732A and the banana plugs of the leads. I have found that even > >> just > >> > > plugging in the lead will generate a thermal difference because of > >> > > difference of temps and some heating due to the physical act of just > >> > > inserting the plug because of friction between the jack and plug (my > >> theory > >> > > at any rate). You have to allow at least a minute or more before > >> being > >> > > able > >> > > to make a measurement after plugging in the leads. I just measured > >> the > >> > > variation of the 1 volt output of my 732A and using my 3458A and I > >> got a > >> > > total difference of 0.159 uV over 40 measurements using 100 PLC on > >> the > >> 1 > >> > > volt range of the 3458A. Using the MATH function and all of the data > >> you > >> > > can collect. That was after waiting for several minutes after > >> plugging > >> in > >> > > the leads. > >> > > > >> > > I hope all of this helps. > >> > > > >> > > Bill > >> > > > >> > > > >> > > > >> > > ----- Original Message ----- > >> > > From: "Randy Evans" <randyevans2688@gmail.com> > >> > > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > >> > > Sent: Friday, August 22, 2014 9:03 PM > >> > > Subject: Re: [volt-nuts] 732A and Prologix received > >> > > > >> > > > >> > > > Todd, > >> > > > > >> > > > Thanks for the info. I have several Panasonic 12V 7 AH batteries > >> that > >> I > >> > > > keep topped off and they have very low current draw (~2 to 3 mA at > >> 13.5 > >> > > > VDC) when charged and at their float voltage, so I am pretty sure > >> they > >> > > are > >> > > > in good condition. I will look at getting those in the units after > >> I > >> > > > ascertain the condition of the 732. > >> > > > > >> > > > So now I have a what appears to be a functioning 3458A and a 732A > >> but > >> > > they > >> > > > slightly disagree. I am like the man with two watches that disagree > >> on > >> > > the > >> > > > time - which is correct? For the moment, i am only concerned with > >> > > > stability. The need for absolute accuracy will come later. > >> > > > > >> > > > Randy > >> > > > > >> > > > > >> > > > On Fri, Aug 22, 2014 at 8:06 PM, Todd Micallef <tmicallef@gmail.com > >> > > >> > > wrote: > >> > > > > >> > > > > Randy, > >> > > > > > >> > > > > You have two possible choices. It can be configured with 4 x 6v > >> 4Ah > >> > > > > batteries or 2 x 12v 7Ah batteries. Hopefully the previous owner > >> has > >> > > > > modified the battery pack already. A couple of mine needed a > >> nibbler > >> > > tool > >> > > > > to remove enough of the aluminum cover that fits over the tops of > >> the > >> > > > > batteries. The original cover will short out to the battery tabs > >> > > regardless > >> > > > > of the battery configuration if this is not done. > >> > > > > > >> > > > > You can find larger capacity batteries that will give you slightly > >> more > >> > > > > battery life. I lost a couple sets of mail-order batteries after a > >> few > >> > > > > extended outages. I would recommend going with locally bought > >> batteries > >> > > > > instead of the cheaper mail order. My local Batteries Plus will > >> > > typically > >> > > > > have some warranty if I remember correctly. Moving forward I will > >> only > >> > > use > >> > > > > 2 12v batteries and pre-charge them on a battery charger to > >> equalize > >> > > them > >> > > > > before putting them in the 732A. I think the cheap batteries did > >> not > >> > > > > discharge equally, and would not recover when power was applied. > >> > > > > > >> > > > > Inspect the back plane for damaged traces and look at the > >> capacitors. I > >> > > had > >> > > > > a few that looked questionable. So far, I have replaced all the > >> big > >> > > caps > >> > > on > >> > > > > the pre-regulator and regulator boards. My feeling is that once > >> these > >> > > go > >> > > > > online, they should run as long as possible between repairs. > >> > > > > > >> > > > > The battery charger circuit may need adjusting. I tweaked mine and > >> it > >> > > > > seemed to work fine. > >> > > > > > >> > > > > Todd > >> > > > > > >> > > > > > >> > > > > On Fri, Aug 22, 2014 at 10:42 PM, Randy Evans < > >> > > randyevans2688@gmail.com> > >> > > > > wrote: > >> > > > > > >> > > > > > I received my Fluke 732A today. Just powered it up but it needs > >> new > >> > > > > > batteries. Any suggestions for sources (I haven't opened up the > >> unit > >> > > > > yet - > >> > > > > > I want to make sure it works before doing that). Also received > >> the > >> > > > > > ProLogix USB-GPIB adapter. I plan on using Mark Sims' CAL ran > >> data > >> > > > > dumper > >> > > > > > program to get the CAL data from my 3458A. Should be a busy > >> weekend. > >> > > > > > > >> > > > > > Randy > >> > > > > > _______________________________________________ > >> > > > > > volt-nuts mailing list -- volt-nuts@febo.com > >> > > > > > To unsubscribe, go to > >> > > > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> > > > > > and follow the instructions there. > >> > > > > > > >> > > > > _______________________________________________ > >> > > > > volt-nuts mailing list -- volt-nuts@febo.com > >> > > > > To unsubscribe, go to > >> > > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> > > > > and follow the instructions there. > >> > > > > > >> > > > _______________________________________________ > >> > > > volt-nuts mailing list -- volt-nuts@febo.com > >> > > > To unsubscribe, go to > >> > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> > > > and follow the instructions there. > >> > > > >> > > _______________________________________________ > >> > > volt-nuts mailing list -- volt-nuts@febo.com > >> > > To unsubscribe, go to > >> > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> > > and follow the instructions there. > >> > > > >> > _______________________________________________ > >> > volt-nuts mailing list -- volt-nuts@febo.com > >> > To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> > and follow the instructions there. > >> > >> _______________________________________________ > >> volt-nuts mailing list -- volt-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > >> and follow the instructions there. > >> > > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

After some more research, I think I've answered some of my own questions - Tellurium copper is used for binding posts, not because it has any special thermal or EMF mojo, but because it machines much better than pure copper. And, I suppose, because it sounds like it's extra special. The Seebeck coefficients (uV/C, relative to Cu) of some relevant materials: Cu 0.0 Ag .2 Au .5 Yellow brass 1.5 Phosphor bronze 2.0 63/37 solder 3.0 Sn 3.1 Stainless steel 3.1 Beryllium copper 5.0 Fe -12.3 Ni 22.3 Te -49.25 Based on the extreme Seebeck coefficient of pure tellurium vs. copper, I'd expect that there might be some coefficient between Cu and CuTe (0.5% Te), but I could find no reference. The relatively large number for CuBe is interesting, since that's a common material for banana plug springs, where one might expect the greatest temperature differential to occur in such a connection (between the thermal masses of the binding post/jack and the bulk of the banana plug). Heat has to flow a considerable distance through the springs, very much more than when it flows through a surface plating. The Pomona (Fluke) EM5295-48-0# uses CuBe (gold plated) for the spring contacts. It seems there might be an improvement to be had by using the older style pin plugs, where a solid pin was partially sliced into 4 sections which were then spread apart a bit to create tension. That could eliminate relatively large thermocouples at a thermal gradient, and might also be expected to have less thermal resistance, allowing the connection to settle quicker. But maybe not - I'm still not clear on how plated conductors behave in this situation. For a high impedance voltage measurement where almost no current flows, the gold plating may carry the signal, so there is no real thermocouple (or more correctly, it's entirely contained within the connector). But if that's the case, why fool around with special copper connectors when common brass ones would be easier/cheaper? For current or resistance, the signal would also flow through the base metal, so does this have an effect (especially for tinned copper test leads, where there may be a larger temperature difference between the ends??? Nickle is avoided as a contact material largely because it is subject to fretting corrosion. Tests done by AMP (http://www.te.com/documentation/whitepapers/pdf/p154-74.pdf) show that a Ni to Ni contact can increase from 8 mOhm to 5 Ohms (sic!) in a short time due to this, while Ag and Au plated contacts exhibit negligible changes. Cu (with Be for better machining) seems to be used as the base material for jacks/plugs to get thermal EMF cancellation to the wiring on both sides (i.e. use copper everywhere except where there is a minimal thermal gradient, like platings). --

Dave, the title is: Thermal Voltage Converters and Comparator for Very Accurate AC Voltage Measurements by E.S.Williams. Adrian > Gesendet: Montag, 25. August 2014 um 19:32 Uhr > Von: "Dave M" <dgminala@mediacombb.net> > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Betreff: Re: [volt-nuts] AC calibration > > Adrian, > Do you have a link or title for the NIST paper that you mentioned? > > Dave M > > > acbern@gmx.de wrote: > > fred, > > generally you raise a good point, I had the same issue of calibrating > > an ac voltage to a high level of accuracy. you need this e.g. to > > validate the self.cal of a 3458a or other precison stuff like the > > 8506a0. > > > > what i would recommend to do if you want to keep costs down is: > > in a nutshell, get a thermal converter in the lowest range you need > > and a second one on range above. build a set of resistor range > > extenders (rf type with appropriate connectors and housings) to > > expand the range to where you need to be max. get one of the thermal > > converter calibrated (the higher one usually, and you need to havr > > good cal lab, should be <10ppm accuracy) and use it to calibrate the > > rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for > > thermal converters! at higher frequencies, due to reflections and > > stray capacitance/inductance influences, the accuracy decreases. the > > resistor range extenders though, if build up correctly, only have a > > few ppm impact (there is a paper from nist on that, but this is only > > typical). you can calibrate all converters to the one you got > > externally calibrated. do some research in the web, when you do the > > calibration, you need to determine the so-called constant N. then do > > an ac, dc+, ac, dc-, ac measurement between the the two and establish > > the deviation, also establish the error propagation. the end result > > will be a set of highly precise (low inaccuracies9 thermal converters > > good enough to calibrate a 3458a an better devices. if you want to > > spend the money, you could also buy a set of converters/range > > resistors (with/without a 540), that typically is a few k altogether, > > while a single device sometimes is available for below 100 bucks. you > > need to have a stable 7.5 digit nanovoltmeter though for the > > measurements of the tvcs (34420a or 2182 typically ) and precision > > (stable) dc and ac sources. but in the end, all you need is a single > > calibrated thermal converter. > > > > adrian > > > > > > > >> Gesendet: Montag, 25. August 2014 um 18:38 Uhr > >> Von: "Dave M" <dgminala@mediacombb.net> > >> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > >> Betreff: Re: [volt-nuts] AC calibration > >> > >> Well, you sort of answered your own question. The equipment is > >> called a Thermal Transfer Standard, but instead of thermistors, it > >> uses a thermocouple. Look at the manual for the Fluke 540B > >> (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how > >> it's done. Basically, the AC source is input into the transfer > >> standard, and the standard's internal reference voltage is adjusted > >> for a null on the galvanometer. Leaving the reference voltage > >> setting alone, a DC voltage is input into the unit, and the DC > >> source is adjusted for a null on the galvanometer. At that point, > >> the AC voltage source is equal to that of the DC voltage source. > >> > >> Ther are thermocouple-type thermal converters used for RF voltage > >> measurements with the transfer standard. They aren't cheap, and you > >> have to have a converter for each range of voltages that you need to > >> measure. The thermal converters used with this type of transfer > >> standard isn't great (50 MHz or so typical), but their accuracy far > >> surpasses that of the thermistor type sensors. > >> > >> There are other brands and models of thermal transfer standards, but > >> I have a Fluke model 540 and a few thermal converters. That's why I > >> referred you to the manual for it. > >> > >> Cheers, > >> Dave M > >> > >> > >> pa4tim@gmail.com wrote: > >>> Is there a way to link an AC voltage to a DC source for compare. I > >>> can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) > >>> against standardcells. But for AC I can not do that. I have two > >>> AC+DC TRMS 7,5 digit meters but the last calibration was 2 years > >>> ago. > >>> > >>> My idea is in theory simple. It is based on the thermal converters > >>> used in RF powermeters. Two resistors, two high resolution > >>> temperature meters. AC on the first en DC on the second. If both are > >>> the same temperature the AC voltage is the same as the DC voltage. > >>> But I'm sure some people here have done this in the past. I would > >>> like to use it for 50 to 100 kHz (or less) and something like for > >>> 1V, 10V and 100V (and use several resistors/heaters.) > >>> > >>> Or mabey there is an other way to convert AC (for RF it can be done > >>> with lightbubs but I never tryed that) I do not mind if it is slow > >>> etc, I like this sort of experiments. You can learn a lot from it. > >>> > >>> Fred, pa4tim > >> > >> > >> _______________________________________________ > >> volt-nuts mailing list -- volt-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow > >> the instructions there. > > _______________________________________________ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > When the people fear the government, there is tyranny. When the > government fears the people, there is liberty -- Thomas Jefferson > > > Dave M > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

-------- In message <trinity-9076c25b-a0a9-4b28-b29a-20f9e06039a3-1409072175101@3capp-gm x-bs56>, acbern@gmx.de writes: Tellurium/copper is used because it machines much better than pure copper, (20% -> 90%) without ruining the conductivity too much. Most other metals which can improve its machinability has big negative impacts on the conductivity of copper. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.