Re: Voltage Calibration Standard

Don Black <donald_black@...>

Probably wet his finger, put it on the 10 volts and could feel the change ;-)

Don Black.
PS Of course, for real accuracy you'd use your tongue!

On 04-Aug-13 2:42 AM, cheater00 . wrote:

On Sat, Aug 3, 2013 at 5:23 PM, Dennis Tillman <dennis@...> wrote:
> The original post was regarding an AD584LH reference which has 4 output
> voltages. Apparently the L version has been discontinued and the remaining
> two versions are not as accurate. The AD584L is laser trimmed to +/-5mV at
> 10.000V and 25 DegC which is +/- 0.05%. This would be more than sufficient
> to use as a calibrated reference for a 0.1% voltmeter which is more than
> enough for 90% of the people doing any home electronics work.
> The temperature coefficient of an AD584LH is 5ppm/degC. Assuming it is used
> as a home reference and the temperature variation is no more than +/-3degC
> in the home that would change the output by +/-15ppm or +/-0.00015V at 10V.
> That is insignificant compared to the 0.05% so it can be ignored.
> Several years ago I bought the Geller Labs PC Board and was quite impressed
> with the overall accuracy of the reference IC that is at its heart. It
> outputs 10.000V +/-5mV. The temperature coefficient is 5ppm/degC. So its
> specifications are comparable to the AD584LH, but it only has one output
> voltage.
> I added an additional 10 turn trim resistor to the Geller Labs reference
> which allowed me to adjust its output to be identical to the DM5120 6 1/2
> digit multimeter I have. The DM5120 is essentially a Fluke instrument
> packaged in a TM5000 case. After a few days I noticed that the DM5120 and
> the Geller Labs board had a repeatable daily variation of a few PPM. The
> sensitivity of the DM5120 was sufficient to measure the temperature
> sensitivity of the Geller Labs board as the temperature of our home dropped
> 3 degrees at night when the thermostat was turned down.
> Dennis

How do you know it wasn't the other way around - the geller staying
constant and the DM being affected?


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