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.
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.
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
| Measurement | Measured Value (on 2018-04-25) | Measured Value (on 2016-05-01 when supplied) | Difference (ppm) | Notes |
|---|---|---|---|---|
| DC Voltage | 4.99996 V | 5.0000 V | 8.0 | |
| DC Current | 0.999936 mA | 0.9999 mA | -36.0 | |
| AC Voltage | 4.99886 V | 4.999 V | 28.0 | |
| AC Current | 0.998765 mA | 1.0000 mA | 1236.5 | Incorrect recording? |
| 100 Ω Resistor | 100.0838 Ω | 100.079 Ω | -48.0 | On 100Ω range |
| 0.100085 kΩ | 0.100079 kΩ | -59.9 | On 1kΩ range | |
| 1 kΩ Resistor | 0.999970 kΩ | 999.94 Ω | -30.0 | On 1kΩ range |
| 1.00002 kΩ | 999.94 Ω | -80.0 | On 10kΩ range | |
| 10 kΩ Resistor | 10.0010 kΩ | 9.9996 kΩ | -140.0 | On 100kΩ range |
| 10.00086 kΩ | 9.9996 kΩ | -126.0 | On 10kΩ range | |
| 100 kΩ Resistor | 0.100093 MΩ | 100.079 kΩ | -139.9 | On 1MΩ range |
| 100.0949 kΩ | 100.079 kΩ | -158.8 | On 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.