Digital ohmmeter with electrical continuity tester

Claim 1

In a digital test instrument for measuring resistance including a pair of input terminals adapted to be connected across a circuit element of unknown resistance, a first reference current or voltage source operatively couple to said input terminals so that an analog voltage appears across said input terminals which is proportional to the resistance of said circuit element, a filter connected to one of said input terminals for filtering noise in said analog voltage, an analog-to-digital converter having an input connected to said filter and an output, a digital display, and driver circuit means connected between said output of said analog-to-digital converter and said digital display, the improvement comprising means for detecting and immediately signalling electrical continuity across said input terminals comprising: s single bit analog-to-digital converter having first and second input terminals, said first input terminal being connected directly to said one of said input terminals, said converter having a sufficiently high input impedance not to affect the operation of said resistance meausring circuitry of said digital test instrument; a secnd source of reference voltage operatively connected to said second input terminal of said single bit analog-to-digital converter, said single bit analog-to-digital converter generating a logical true or logical false signal depending upon whether said analog voltage is higher or lower than said second reference voltage; a digital continuity display; an driver circuit means connected between said single bit analog-to-digital converter and said digital continuity display for instantaneously indicating continuity.