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This is the accuracy spec for an Agilent 34401A 6-1/2 digit multimeter. What exactly does the "temperature coefficient" mean here? Does it mean that the reading will not change by more than 0.0005% (5 ppm) over the whole temperature range 0 to 18C? Or does it mean 5 ppm/C? And why are there two separate temperature ranges 0-18 and 28-55? (I understand that it gives % of reading plus % of range.) Agilent 34401A multimeter DC volts accuracy specification

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  • \$\begingroup\$ Accuracy at 23+/-5C includes any temperature error already. Outside that, add the temperature error (calculated per answers) to the base accuracy figure. \$\endgroup\$ Mar 9, 2021 at 0:52
  • \$\begingroup\$ Got it. Very confusing to me at first sight because they missed the /C, and because there is a tempco between 18 and 28C, but its contribution to the accuracy is already included in the other specs. \$\endgroup\$
    – 10ppb
    Mar 9, 2021 at 1:11

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If you look at the manual for the 34401A multimeter, you will find that the specification you quoted in your question is missing some information. In the manual, the same specs appear except that in the last column the term "temperature coefficient" is directly followed by "/°C" which indicates that the numbers are to be taken as per °C. This makes sense since the number applies over a range of 0-18C (span of 18 deg) and a range of 28-56C (a span of 28 deg). A drift of 5ppm per degree C is a lot more reasonable than a drift of 5ppm over a span of 28 deg (equivalent to a drift of only 0.18ppm per deg).

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  • \$\begingroup\$ That’s helpful. The clip I posted is from the Agilent data sheet. It clarifies things to know there is a “/C” in the manual. This still does not explain the temperature ranges, but I found a similar spec in a Fluke publication that is more clear. I think we are supposed to understand that there is no additional error related to temperature between 18 and 28 C. Then we add 5 ppm/C of reading and 1 ppm/C of range for every degree C above 28 C or every degree C below 18 C. There is no spec below 0 C or above 55 C. \$\endgroup\$
    – 10ppb
    Mar 9, 2021 at 0:20
  • \$\begingroup\$ There is no additional error for temperatures between 18 and 28C because they are covered in the 90 day and 1 year columns.. Temperatures below 0C and above 55C are out of the multimeters operating temperature limits. \$\endgroup\$
    – Barry
    Mar 9, 2021 at 3:00
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No, "coefficient" means factor by which temperature change is multiplied.

I.E., using the 100,000 mV range at full scale (0.1V), a change from 0°C to 18°C. a 18°C rise, could change reading by as much as 18 x 0.0005% = 0.009% (ignoring the additional error allowance of 0.0005) x 200,000 mV [% reading + % range] = 0.0018 V. (Hoepfully, I've kept track of the decimal place... verification is left to the student ;-)

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