Hello Stephen, I agree that the 4920's will often drift more than their spec after 1 year. I find it more convenient to derate them slightly - and use them wisely. Note the manual states their absolute specs are valid for 6 months, but I still maintain them on a 1 year cycle. Even when de-rated they still have very good short term stability over 10 minutes and for weeks after. On the discussion of inputs at low points in ranges, I find this is where the 4920M's will most often cause calibration failures against their specs. Perhaps optimistically, Datron has specified their absolute reading spec at, say, 3V range, to be +-30ppm of reading (40 to 20kHz) for any input from 30% to 100% of range. No floor or percentage of range limiting spec is stated. When the sad day finally arrives and I need to repair units I would resort to cannibilising parts from these 4920M's just to keep my more capable 4920 going. regards, ben. ---------------------------------------- From: "Stephen Grady" <grady.steve@gmail.com> Sent: Monday, September 01, 2014 5:37 AM To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Charlie, The "Error Ur" is an under-range error; you have to apply an input above 10% of the range before it will display a reading. The 4920's are a very nice instrument. Their only problem is that they are all so old that they are reaching the stage where some components are drifting excessively or failing. I have come across 4920's that are drifting a little (more than there spec) between cals (and yes they need to be cal'd annually), another 4920 I came across had an intermittent failure in one of its power supplies. Kind Regards, Stephen Grady Sydney Australia -----Original Message----- From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Charles Black Sent: Monday, 1 September 2014 3:19 AM To: ben@veritechmeasurements.com.au; Discussion of precise voltage measurement Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Ben, I am going to check this out today to find if it might be helpfull around here for my AC calibration. It has an error message: "Error Ur" so some fixing is going to be needed. On the back it says it's got Option 80, whatever that is. Charlie On 8/31/2014 5:37 AM, ben wrote: > Hello all, > Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC > voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I > have little idea of its true working state or not (picture shows it powered on). > If fully working it would be a good buy for an AC voltmeter that is, I > reckon, better than an HP 3458A. Only drawback with these models is > the voltage input shell is always earthed, not floating. I have two of > these 4920M's already, not really tempted by a third. I have a paper > copies of operator, calibration, and service manual if anyone interested. > > regards, ben. > _______________________________________________ > 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. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _______________________________________________ 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.

Hi, The auction winning bid was $1432. I was outbid by two people and never had an effect on the auction at all! Charlie On 9/1/2014 1:51 AM, ben wrote: > Hello Stephen, > I agree that the 4920's will often drift more than their spec after 1 year. > I find it more convenient to derate them slightly - and use them wisely. > Note the manual states their absolute specs are valid for 6 months, but I > still maintain them on a 1 year cycle. Even when de-rated they still have > very good short term stability over 10 minutes and for weeks after. > > On the discussion of inputs at low points in ranges, I find this is where > the 4920M's will most often cause calibration failures against their specs. > Perhaps optimistically, Datron has specified their absolute reading spec > at, say, 3V range, to be +-30ppm of reading (40 to 20kHz) for any input > from 30% to 100% of range. No floor or percentage of range limiting spec is > stated. > > When the sad day finally arrives and I need to repair units I would resort > to cannibilising parts from these 4920M's just to keep my more capable 4920 > going. > > regards, > ben. > > > > > > ---------------------------------------- > From: "Stephen Grady" <grady.steve@gmail.com> > Sent: Monday, September 01, 2014 5:37 AM > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 > day left > > Charlie, > > > The "Error Ur" is an under-range error; you have to apply an input above > 10% of the range before it will display a reading. The 4920's are a very > nice instrument. Their only problem is that they are all so old that they > are reaching the stage where some components are drifting excessively or > failing. I have come across 4920's that are drifting a little (more than > there spec) between cals (and yes they need to be cal'd annually), another > 4920 I came across had an intermittent failure in one of its power > supplies. > > Kind Regards, > > Stephen Grady > Sydney Australia > > -----Original Message----- > From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Charles > Black > Sent: Monday, 1 September 2014 3:19 AM > To: ben@veritechmeasurements.com.au; Discussion of precise voltage > measurement > Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 > day left > > Hi Ben, > > I am going to check this out today to find if it might be helpfull around > here for my AC calibration. It has an error message: "Error Ur" > so some fixing is going to be needed. On the back it says it's got Option > 80, whatever that is. > > Charlie > > > On 8/31/2014 5:37 AM, ben wrote: >> Hello all, >> Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC >> voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I >> have little idea of its true working state or not (picture shows it > powered on). >> If fully working it would be a good buy for an AC voltmeter that is, I >> reckon, better than an HP 3458A. Only drawback with these models is >> the voltage input shell is always earthed, not floating. I have two of >> these 4920M's already, not really tempted by a third. I have a paper >> copies of operator, calibration, and service manual if anyone interested. >> >> regards, ben. >> _______________________________________________ >> 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. > > > --- > This email is free from viruses and malware because avast! Antivirus > protection is active. > http://www.avast.com > > _______________________________________________ > 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. > > >