MAX6350 ?
Maxim has a buried zener voltage reference called MAX6350, but it is
specified for "instant precision", not long term drift (30ppm/1000h).
Have any of you by any chance found/collected data on the long term
performance of these ?
--
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.
In message 84314.1283455235@critter.freebsd.dk, Poul-Henning Kamp writes:
Maxim has a buried zener voltage reference called MAX6350, but it is
specified for "instant precision", not long term drift (30ppm/1000h).
Replying to myself here:
First a bit of background: I use voltage references in electronics
from time to time, and have kept a lazy eye on new products.
The MAX6350 ended up in a 12bit ADC application we could never
expect to calibrate over its decadal lifetime. Recently one of
these gadgets came back to my lab and I was pleased to see the Vref
hold op really well.
There are other new-ish Vref products and, more interesting, new
technologies, such as Analog Devices "XFET" etc[1]. None of these
Vref's are really spec'ed for metrology grade apps, their long-term
specs are really just "burn-in" indications.
I could not help wondering if any of these new chips had metrology
potential. If properly ovenized and protected, they might even give
the 20 year old LZ1000ACH design a run for the money.
I put a MAX6350 from the parts-drawer in a breadboard, added some
1µF tantallum capacitors, used a LM358 opamp as pre-regulator to
feed it 10V supply, referenced to its own 5V output (the MAX6350
has pretty bad supply sensitivity), put a piece of bubble-wrap over
it, and left my HP3458A chug along for a week. I did nothing to
protect the 3458A's input electrodes from airflow and nothing
to deal with seebek etc, just random lab-wires used.
I have filtered out 91 of 172k measurements, because they were more
than 5 stddevs out, I have not tried to find out what caused them,
probably people turning flouresent lights on and off.
Here is the result as 3 hour averages+standard deviations, relative to
the global average of 4.999705193 V
http://phk.freebsd.dk/misc/20100911_max6350_1.png
And here also with the original raw data:
http://phk.freebsd.dk/misc/20100911_max6350_2.png
Since this is a 5V reference, the Y-scale corresponds to +/- 1 PPM.
The 3-hour standard deviation is quite constant at 0.12 .. 0.18 PPM
and the average is +/- 1PPM over 8 days. Comparing to other data
collection in the lab, I am confident that residual is mostly tempCo.
All in all: I'm pretty impressed.
Poul-Henning
[1] Analog got a bit smart&silly with the long term spec, and got
soundly and deservedly beaten up by linear.com (DN229) for that,
but that doesn't mean that the XFET's are not interesting, it only
means that they are not revolutionary.
--
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.
There are other new-ish Vref products and, more interesting, new
technologies, such as Analog Devices "XFET" etc[1]. None of these
Vref's are really spec'ed for metrology grade apps, their long-term
specs are really just "burn-in" indications.
I have examined some Intersil FGA-Reference which is specified with 0.5mV @
5V. (0.01%)
The ISL21009BFB850 has a "switch off" hysteresis. When switching off for a
(very) short time
the reference voltage starts with a about 200 uV lower voltage. It needs
several days until the
previous voltage is reached again. According to Intersil all "low power"
references have
a longer startup-time.
I have filtered out 91 of 172k measurements, because they were more
than 5 stddevs out, I have not tried to find out what caused them,
probably people turning flouresent lights on and off.
Are these values in row or are they randomly distributed?
On my measurements with MAX6250 I had some strange "jumps" of about 7uV
for some minutes in one direction and back after the minutes when doing the
temperature cycling.
The jumps could be repeated on the next temperature cycling. The temperature
of the jumps was not
constant but near the temperature of the previous cycling.
Best regards
Andreas
In message C83AF32E80E84C99A35CDB938BB67EC7@laptop, "Andreas Jahn" writes:
I have filtered out 91 of 172k measurements, because they were more
than 5 stddevs out, I have not tried to find out what caused them,
probably people turning flouresent lights on and off.
Are these values in row or are they randomly distributed?
These were random single events.
On my measurements with MAX6250 I had some strange "jumps" of about 7uV
for some minutes in one direction and back after the minutes when doing the
temperature cycling.
I do have some weird short term effects in my data, (they are
included in the avg/stddev calculations) but I do not know the cause
at this point in time.
It does not surprise me the least if these devices suffer from
thermal stress effects, they are just plain expoxy moulded devices.
Poul-Henning
--
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.
Hello, new guy here.
I recently acquired an old fluke 801 differential voltmeter, and removed
the Muirhead Weston cell from it.
I'm not sure if it is the original cell or not, I don't doubt it.
In any case, it was mounted upside down for what had to be a number of
years, and there are several tiny balls of mercury loose.
Compounding this issue, it does not work right side up, past 30 degrees
from horizontal it is as if it turned off.
My thoughts are this is due to the mercury detaching from the platinum
wire, it works great lying flat on the table.
In any case i took it to work last week and did some measurements,
however the best i could do at the time is verify that it is delivering
1.0190 +/- .05mV volts.
(This was at 18 degrees Celsius)
I'm in the process of building an oil bath and temperature regulator for
it, and by that time i should be able to find the 732b at work and get a
more accurate measurement.
My question is there any good reason why is it nearly half a millivolt
over what the old books say it should be?
thanks,
Eldon Johansen
eldon.johansen@gmail.com
Did you remove it from a temperature-controlled enclosure? If not, it's
an unsaturated cell and 1.019XX V is correct. If yes, then it's a
saturated cell and the voltage is a little high. I have a couple of
Muirhead saturated cells that are spec'ed at 1.01877 V @ 15 C and
1.01859 V @ 20 C.
Ed
Eldon Johansen wrote:
Hello, new guy here.
I recently acquired an old fluke 801 differential voltmeter, and removed
the Muirhead Weston cell from it.
I'm not sure if it is the original cell or not, I don't doubt it.
In any case, it was mounted upside down for what had to be a number of
years, and there are several tiny balls of mercury loose.
Compounding this issue, it does not work right side up, past 30 degrees
from horizontal it is as if it turned off.
My thoughts are this is due to the mercury detaching from the platinum
wire, it works great lying flat on the table.
In any case i took it to work last week and did some measurements,
however the best i could do at the time is verify that it is delivering
1.0190 +/- .05mV volts.
(This was at 18 degrees Celsius)
I'm in the process of building an oil bath and temperature regulator for
it, and by that time i should be able to find the 732b at work and get a
more accurate measurement.
My question is there any good reason why is it nearly half a millivolt
over what the old books say it should be?
thanks,
Eldon Johansen
eldon.johansen@gmail.com
I should have mentioned, It is a saturated cell.
Originally it was wrapped in aluminum foil and was held in place with a
half inch thick foam pad on either side in the volt meter.
i removed it from that and it held it in my hand on the way to work,
then let it sit on the counter for 6 hours before measuring it.
there wasn't but a 5C difference between here and work, it had sat here
a week, so i figured it would be in the ballpark.
I was more concerned about my standards reading a millivolt high than
the life of this cell. The vibration didn't help either.
I thought for sure the old weston cells were supposed to be 1.0183xx
anyhow, thanks for the information.
Eldon Johansen
Eldon.johansen@gmail.com
On Sun, 2010-09-12 at 22:11 -0600, Ed Palmer wrote:
Did you remove it from a temperature-controlled enclosure? If not, it's
an unsaturated cell and 1.019XX V is correct. If yes, then it's a
saturated cell and the voltage is a little high. I have a couple of
Muirhead saturated cells that are spec'ed at 1.01877 V @ 15 C and
1.01859 V @ 20 C.
Ed
Eldon Johansen wrote:
Hello, new guy here.
I recently acquired an old fluke 801 differential voltmeter, and removed
the Muirhead Weston cell from it.
I'm not sure if it is the original cell or not, I don't doubt it.
In any case, it was mounted upside down for what had to be a number of
years, and there are several tiny balls of mercury loose.
Compounding this issue, it does not work right side up, past 30 degrees
from horizontal it is as if it turned off.
My thoughts are this is due to the mercury detaching from the platinum
wire, it works great lying flat on the table.
In any case i took it to work last week and did some measurements,
however the best i could do at the time is verify that it is delivering
1.0190 +/- .05mV volts.
(This was at 18 degrees Celsius)
I'm in the process of building an oil bath and temperature regulator for
it, and by that time i should be able to find the 732b at work and get a
more accurate measurement.
My question is there any good reason why is it nearly half a millivolt
over what the old books say it should be?
thanks,
Eldon Johansen
eldon.johansen@gmail.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.