Recheck of a DMMCheck+

Several years ago I was given a DMMCheck+ as a birthday present. They are very handy little devices which provide AC and DC voltage and current, four resistance values. These are all at about 0.1% precision and frequency and duty cycle are also provided. All of this fits within a battery powered compact 3 inch cube. Unfortunately VoltageStandard.com discontinued the DMMCheck+, but checking the site recently shows that it may be back in production (but currently sold out). I use it to periodically check my HP3478A at home but as part of the check on the precision resistors, I decided to remeasure it with work’s Agilent 34410A to see if it had changed significantly.

DMMCheck+ being tested on the bench for resistance values
DMMCheck+ being tested on the bench for resistance values

Procedure and Measurements

The measurements used a Agilent HP34410A that was available at work. According to the unit, it was last calibrated in January 2007. The number of power line rejection cycles (NPLC) was set to 100. For the AC measurements, the Slow 3 Hz mode was used.  4 wire Kelvin clips were used for the resistance and voltage measurements and Pomona DMM leads were used for the current.

Measuring the 10 kOhm 0.1% precision resistor on the DMMCheck+. Value is 10.00091 kOhm
Measuring the 10 kOhm 0.1% precision resistor on the DMMCheck+

Here are the measured values and the comparison to the supplied spec. sheet. This was measured by VoltageStandard.com with an 8.5 digit 3458A DMM which had been recently calibrated.

 

DMMCheck+ Measured Values

MeasurementMeasured Value (on 2018-04-25)Measured Value (on 2016-05-01 when
supplied)
Difference (ppm)Notes
DC Voltage4.99996 V5.0000 V8.0

DC Current0.999936 mA0.9999 mA-36.0
AC Voltage4.99886 V4.999 V28.0
AC Current0.998765 mA1.0000 mA1236.5Incorrect recording?
100 Ω Resistor100.0838 Ω100.079 Ω-48.0On 100Ω range
0.100085 kΩ0.100079 kΩ-59.9On 1kΩ range
1 kΩ Resistor0.999970 kΩ999.94 Ω-30.0On 1kΩ range
1.00002 kΩ999.94 Ω-80.0On 10kΩ range
10 kΩ Resistor10.0010 kΩ9.9996 kΩ-140.0On 100kΩ range
10.00086 kΩ9.9996 kΩ-126.0On 10kΩ range
100 kΩ Resistor0.100093 MΩ100.079 kΩ-139.9On 1MΩ range
100.0949 kΩ100.079 kΩ-158.8On 100kΩ range

Summary

With the exception of the AC current, which may have been incorrectly written down, everything shows small changes in two years. The original measurements with the 3458A will have measured the DC voltage to 8 ppm, and resistance to ~10 ppm. However the spec on the 34410A is not as good (about 30ppm on DC volts). It also hasn’t been calibrated in 10 years. Also bear in mind that the 0.1 % specs for the DMMCheck+ corresponds to 1000 ppm (parts per million) for the initial accuracy.