Amprobe MO-100 Manual do utilizador - Página 13

Procurar online ou descarregar pdf Manual do utilizador para Instrumentos de medição Amprobe MO-100. Amprobe MO-100 18 páginas. Milliohm meter

Thermal Effects

• Temperature can have a significant effect on the performance of a

milliohm meter due to the temperature coefficient of the resistance

under test and thermal EMF's across the dissimilar conductors.

• Most conductors have a large temperature coefficient of resistance. For

example: 0.4%/°C for copper. A copper conductor that has a resistance

of 10.00m ohm at 20°C will increase to 10.40m ohm at 30°C. This change

should be taken into account when making measurements.

• A current going through a resistance will also elevate its temperature. So

duration of the test can change the resistance.

• When measuring the resistance of item, such as current shunts, which

have joints of dissimilar conductors, thermal EMF can affect the accuracy

of the measurement. This condition can be detected if the reading alters

when the leads are reversed. To compensate for this effect, the average

of the two readings should be taken as the true measurement.