Non-linearity in a voltmeter using cathode-follower and thermocouple
David Gorda Tucker · Journal of Scientific Instruments · 1953
The problem analysed in this paper is that of the error due to value non-linearity in an instrument comprising a galvanometer connected to a thermocouple, the heater of which is used as the cathode load of a cathode-follower; such an instrument enables measurements of a.c. voltages, whether sinusoidal or complex, to be made against a d.c. standard without appreciable loading of the source. One cause of error is evidently the effect of valve non-linearity, since the a.c. and d.c. inputs produce very different swings of grid voltage. The analysis shows, however, that this error is usually very small, and in a good design need not prevent a voltage of about 0.8 V being standardized to 0.1%.