Patent ID: 7652472
Filing Date: 2010-01-26
Classification: G01R

Abstract:
1. A signal detection circuit of a magnetic sensor including an exciting coil and a detecting coil, the signal detection circuit comprising: a voltage adjusting circuit to set a DC voltage level of the detecting coil to a predetermined DC voltage level; a differential amplifier to be applied with an output voltage of the detecting coil at a time when a first drive signal is applied to one terminal of the exciting coil and a second drive signal is applied to the other terminal of the exciting coil, the second drive signal being a signal inverted in polarity with respect to the first drive signal as well as intersecting with the first drive signal twice or more; a comparator to which an output of the differential amplifier is input, the comparator outputting a digital signal having one logical value during a period defined between two adjacent spike voltages included in the output voltage due to intersection of the first drive signal and the second drive signal; a counter that counts a number of pulses of a clock in a period when the output of the comparator has one logical value; and a control circuit connected communicably to an external apparatus, the control circuit including a memory configured to store a count value of the counter.