Diagnostic circuit for testing a circuit

Abstract

A diagnostic circuit is configured for connecting to a unit under test that has a load and a sinusoidal source. The diagnostic circuit includes a voltage sensing device that has an input for sensing a signal, a first terminal for connecting to the load, a second terminal for connecting to the sinusoidal source, and a relay connected between the first and second terminals for connecting the sinusoidal source to the load. Clamping diodes are provide for clamping a sinusoidal signal and include a first clamping diode connected between a D/C voltage source and the input and a second clamping diode connected between ground and the input. A resistor is connected between the D/C voltage source and the first terminal. The diagnostic circuit verifies the operational functionality of the load, related wiring and connections.

We claim: 
     
         1 . A diagnostic circuit for connecting to a unit under test having at least two loads, the diagnostic circuit comprising:
 terminals including a first terminal for connecting to a first load and a second terminal for connecting to a second load   a voltage sensing device having an input for sensing a signal and coupled to said terminals;   a D/C source and ground;   a first resistor having a first end connected to said D/C source and a second end connected to said first terminal; and   a second resistor having a first end connected to said D/C source and a second end connected to said second terminal.   
     
     
         2 . The diagnostic circuit according to  claim 1 , further comprising a resistor connected between each of said terminals and said input. 
     
     
         3 . 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;   terminals including first terminals for connecting to the load and a second terminal for connecting to the sinusoidal source;   a relay connected between one of said first terminals and said second terminal 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;   a first capacitor connected between said ground and a first one of said first terminals; and   a second capacitor connected between said clamping diodes and a second one of said first terminals.   
     
     
         4 . The diagnostic circuit according to  claim 3 , further comprising at least one resistor connected between said input and one of said first and second capacitors. 
     
     
         5 . 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 a first input for sensing a signal and a second input;   terminals including a first terminal for connecting to the load and a second terminal for connecting to the sinusoidal source;   a relay connected between said first terminal and said second terminal 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;   a first capacitor connected between said first terminal and said first input; and   a second capacitor connected between said second terminal and said second input.   
     
     
         6 . The diagnostic circuit according to  claim 5 , further comprising at least one resistor connected between said first input and said first capacitor. 
     
     
         7 . A diagnostic circuit for connecting to a unit under test having a load and three lines of a sinusoidal source, the diagnostic circuit comprising:
 a voltage sensing device having a first input and a second input;   terminals including first terminals for connecting to the load and second terminals for connecting to two lines of the sinusoidal source;   relays each connected between one of said second terminals and one of said first terminals for connecting the sinusoidal source to the load;   a D/C voltage source and ground;   a first diode pair having a first clamping diode connected between said D/C voltage source and said first input and a second clamping diode connected between said ground and said first input;   a second diode pair having a first clamping diode connected between said D/C voltage source and said second input and a second clamping diode connected between said ground and said second input;   a first capacitor connected between a first of said first terminals and said first input; and   a second capacitor connected between a second of said first terminals and said second input.   
     
     
         8 . The diagnostic circuit according to  claim 7 , further comprising a third capacitor connected between a third line of the sinusoidal source and said ground. 
     
     
         9 . The diagnostic circuit according to  claim 7 , further comprising at least one resistor connected between said first input and said first capacitor. 
     
     
         10 . The diagnostic circuit according to  claim 7 , further comprising at least one resistor connected between said second input and said second capacitor.