in the system cabling as shown below to attenuate instrument emissions.
Thermal EMFerrors
Thermoelectric voltages are the most common source of error in low-level DC voltage measurements.
Thermoelectric voltages are generated when you make circuit connections using dissimilar metals at dif-
ferent temperatures. Each metal-to-metal junction forms a thermocouple, which generates a voltage pro-
portional to the junction temperature difference. You should take the necessary precautions to minimize
thermocouple voltages and temperature variations in low-level voltage measurements. The best con-
nections are formed using copper-to-copper crimped connections. The table below shows common ther-
moelectric voltages for connections between dissimilar metals.
Copper-to- Approx. µV/°C
Copper <0.3
Gold 0.5
Silver 0.5
Brass 3
Beryllium Copper 5
Aluminium 5
Kovar or Alloy 42 40
Silicon 500
Copper-Oxide 1000
Cadmium-Tin Solder 0.2
Tim-Lead Solder 5
4Measurement Tutorials
180 Keysight DAQ970A User's Guide
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