The thermal EMF measurement methods for multichannel scanners

In the precision measurement system with a multichannel scanner, the thermal electromotive force (EMF) of the scanner should be considered properly. Two kinds of the thermal EMF measurement method are discussed in this paper, which correspond respectively to the systems based on the direct measuring instruments and the comparison measuring instruments. For the direct measurement system, the thermal EMF of each channel is measured. For the comparison system, the thermal EMF of different pairs of channel are measured and the least squares method is used to estimate the effect to the comparison measurement. Examples are also given to illustrate the two methods based on the homemade scanner.