Dc Measurement Considerations; Table 3-1 Thermoelectric Voltage For Dissimilar Metals Connections - Agilent Technologies U2741A User Manual

3 Measurement Tutorial

DC Measurement Considerations

48
Thermal EMF errors
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 different temperatures.
Each metal- to- metal junction forms a thermocouple, which
generates a voltage proportional to the junction temperature.
You should take the necessary precautions to minimize
thermocouple voltages and temperature variations in
low- level voltage measurements. The best connections are
formed using copper- to- copper crimped connections, as the
digital multimeter's input terminals are copper alloy. The
table below
shows common thermoelectric voltages for connections
between dissimilar metals.

Table 3-1 Thermoelectric voltage for dissimilar metals connections

Copper to - Approx. mV / °C
Cadmium-Tin Solder 0.2
Copper <0.3
Gold 0.5
Silver 0.5
Brass 3
Beryllium 5
Copper to - Approx. mV / °C
Aluminum 5
Tin-Lead Solder 5
Kovar or Alloy 42 40
Silicon 500
Copper-Oxide 1000
U2741A User's Guide