JPH0350225B

PURPOSE:To enable to perform an easy and reliable detection of the presence of a trouble on a DC solenoid device, by comparing an initial change property of an exciting current with a value at a normal time. CONSTITUTION:A current transformer 6 detects an exciting current of a DC soleniod device 1 at a closing time of a switch 4 to determine a peak value by means of a peak hold circuit 7. When a positive peak value P is applied to a processor 10 vai an A/D converter 9, an FF12, simultaneously, is set by a pulse generating circuit 11 actuating in response to the peak value. A negative peak value is determined in a similar manner by an inversion current running through an inversion circuit 13, a negative peak value Q, being A/D-converted, is inputted to the processor 10, and the FF12 is reset to apply the set output of the FF12, corresponding to a period DELTAf between the positive and negative peak values, to the processor 10. The positive and negative peak values P and Q, being stored in a memory 19 in the processor 10 and being under a normal condition, are compared with the initial charge property of the period DELTAf between the two peak values, and this simply and reliably detects the presence of a trouble on the DC solenoid device. Accordingly, the size precision of the solenoid device can also be ascertained.