Patent ID: 9322871
Filing Date: 2016-04-26
CPC Classification: G01R

Claim Text:
1. A current measurement circuit comprising: a first input node and second input node which respectively receive a voltage from either side of a resistive element through which electrical current can flow; a differential amplifier, which produces an output signal indicative of the difference in voltage between its input terminals; electrical path forming means providing a connection between each of said input nodes and a respective input terminal of said differential amplifier; a controllable voltage source for selectively applying an offset voltage to at least one input of said differential amplifier in response to a control signal; a control signal generator which generates said control signal applied to said voltage source such that at a first instance an offset voltage is applied which is greater than the offset voltage applied at a second instance, and a diagnostic means which identifies faults present in said electrical path between said first input node and said respective input to said amplifier by comparing the output from said amplifier at said first instant with the output at said second instant and further in which said diagnostic means produces an error signal indicating a fault in the event that said difference between the output of said amplifier at said first instant and said output at the second instant is less than a predetermined threshold level, wherein either: said voltage source is adapted to apply an offset voltage to just one input terminal of said amplifier; or said control means causes said circuit to perform at least one of the following functions: (a) applying an offset voltage to said positive terminal at said second instant but not to said negative terminal, and to apply no offset voltage at said first instant; (b) applying an offset voltage to said negative terminal at said second instant but not to said positive terminal, and to apply no offset voltage at said first instant; and (c) applying an offset voltage to both said positive terminal and said negative terminal at said second instant but apply no offset voltage at said first instant.