It's been more than 6 weeks since I powered on the new voltage reference. It has been running continuously, except for 2 relatively short power outages. Time to find out what sort of drift is happening. Here's the data:
Temperature = 64F (~18C), HighZ input, 100plc
Reading Scale Other Error Drift
99.9913mV - 99.993mV 100mV Null, Avg 20 samples ~-8uV +1.4uV (14ppm)
1.0000829V 1V Avg 20 samples +83uV -0.4uV (-0.4ppm)
10.000070V 10V Avg 20 samples 70uV +83uV (8.3ppm)
I'm satisfied with these results. The biggest surprise is the 10V reading drifting nearly 10ppm, but it doesn't require any adjustment since it is within 100uV of the target. I'll just record these numbers on the box and use them to compare readings in the future.
Note that the 100mV reading is a range. I left the meter run continuously over several days and made multiple readings. Every time I took a null measurement and replaced the probes it would be a slightly different reading. I'm going to chalk that up to thermoelectric noise and move on.
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