Patent ID: 6577133
Filing Date: 2003-06-10
Classification: B60T,F15B,G01R

Abstract:
An apparatus for testing a solenoid valve cartridge having a magnetic circuit that includes a stationary portion and a moveable armature, the apparatus for testing comprising:a test coil adapted to be placed over the solenoid valve cartridge, said test coil having a first end and a second end; a current sensing resistor connected to said first end of said coil; a switching device having first and second terminals and a control port, said switching device being responsive to a voltage applied to said control port to be in one of a conducting state and a non-conducting state between said first and second terminals, said switching device first terminal being connected to said second end of said test coil; a power supply connected to said switching device second terminal; a control circuit having an output terminal connected to said switching device control port, said control circuit also having input terminals connected across said current sensing resistor, said control circuit co-operating with said test coil to form an oscillatory circuit that applies an oscillating voltage to said switching device control port, said switching device being responsive to said oscillating voltage to be in a conducting state when the current through said current sensing resistor falls below a first predetermined value, and to be in a non-conducting state when the current through said current sensing resistor exceeds a second predetermined value that is greater that said first predetermined value, the switching device applying a pulsed voltage to said test coil with the on time of the voltage pulses being a function of the length of a working air gap between the stationary part and the movable armature in the magnetic circuit of the solenoid valve cartridge; and a measuring device connected to said control circuit, said measuring device operative to determine the average on time of the voltage pulses applied to the test coil and to correlate said average pulse on time to the size of the working air gap to provide an indication of proper operation of the solenoid valve cartridge.