Patent ID: 8013615

Claim:
A diagnostic circuit for connecting to a unit under test having a load and a sinusoidal source, the diagnostic circuit comprising: a voltage sensing device having an input for sensing a signal; a first terminal for connecting to the load and a second terminal for connecting to the sinusoidal source; a relay connected between said first and second terminals for connecting the sinusoidal source to the load; a D/C voltage source and ground; clamping diodes including a first clamping diode connected between said D/C voltage source and said input and a second clamping diode connected between said ground and said input; and a resistor connected between said D/C voltage source and said first terminal; wherein said voltage sensing device is a micro-controlled analog to digital converter circuit; and wherein said relay has an open state in which said first terminal and said second terminal are not connected together, and the sinusoidal source is disconnected from said voltage sensing device when said relay is in the open state.