To achieve the greatest accuracy with the Keysight Truevolt Series multimeters, you must eliminate potential measurement errors. This chapter describes common errors and suggests ways to avoid them.
The 34470A 7½-digit DMM is well-suited for high-accuracy metrology applications. Keysight has a number of application notes pertaining to maximizing measurement accuracy, such as:
Practical Tips for Optimizing Measurement Accuracy with your Digital Multimeter -This Web page has a number of links to application notes addressing DMM measurement errors and how to make temperature measurements.
Making Better Measurements with your Digital Multimeter - This Web page has a number of links to application notes addressing better RMS measurements, system cabling errors, DC, frequency, and period measurement errors, and AC voltage measurement errors.
Make Better AC Measurements with Your Digital Multimeter - Focuses on AC measurement accuracy.
Make Better RMS Measurements with Your Digital Multimeter - Focuses on RMS measurement accuracy.
Practical Temperature Measurements - A detailed tutorial describing how to make accurate temperature measurements.
Search www.keysight.com for application notes that address your measurement and accuracy needs.
Thermoelectric voltages are the most common error source in low–level DC voltage measurements. Thermoelectric voltages are generated by circuit connections using dissimilar metals at different temperatures. Each metal–to–metal junction forms a thermocouple that generates a voltage proportional to the junction temperature, as shown in the table below. You should minimize thermocouple voltages and temperature variations in low–level voltage measurements. The best connections use copper–to–copper crimped connections, as the DMM’s input terminals are a copper alloy.
| Copper to: | Approx. µV / °C |
|---|---|
| Cadmium-Tin Solder | 0.2 |
| Copper | <0.3 |
| Gold | 0.5 |
| Silver | 0.5 |
| Brass | 3 |
| Beryllium Copper | 5 |
| Aluminum | 5 |
| Tin-Lead Solder | 5 |
| Kovar or Alloy 42 | 40 |
| Silicon | 500 |
| Copper Oxide | 1000 |
Measurement loading errors occur when the resistance of the DUT is an appreciable percentage of the multimeter's input resistance, as shown below.
To reduce the effects of loading errors and to minimize noise pickup, set the multimeter's input resistance to >10 GΩ (high-impedance) for the 100 mVDC, 1 VDC, and 10 VDC ranges. The input resistance is maintained at 10 MΩ for the 100 VDC and 1000 VDC ranges.