GB1288988A - - Google Patents

Abstract

1288988 Compensating for lead impedances LICENTIA PATENT-VERWALTUNGS GmbH 13 Nov 1970 [15 Nov 1969] 54234/70 Heading G1U In order to obtain, independently of lead impedances, a measure of the potential across a sensing element 3, Fig.1, as a result of passing a constant current from a generator 9 through it, rather than using two additional voltage sensing leads, one extra lead 4 and one extra identical constant current generator, connected as shown, are used. The potential across terminals 6 and 7 of the constant current generators, which may be amplifier 14 and indicated 17 in any appropriate manner, is then a measure of the required potential. This is so because the leads 4 and 5 will both carry the same current in a direction towards the sensing element, and therefore the voltage drops across them are of equal magnitude and when seen from terminals 6 and 7 are in series opposition. The saving of one lead to the sensing element is particularly worthwhile when the leads are long and when a plurality of sensing elements are sequentially monitored from a remote point (as in Fig. 2, not shown).