Importance

Loading Importance Indicators...

Abstract

Sensor circuitry is disclosed for a transducer (32) having a sensor or delta coil (66) for generating a magnetic flux through a path of movement of a magnetically permeable piston member (48), such that movement of the member (48) changes the return coupled flux linkage, which flux change indicates movement of the member (48), and having a reference coil (84) spaced sufficiently from the path of movement of the member (48) such that movement of the latter has less affect on return coupled flux linkage of the reference coil (84) than the delta coil (66). The coils (66 and 84) are connected (204) in respective parallel voltage dividers, and a half-wave rectified AC signal (diode CR11) is applied thereto. A differential amplifier (210) senses the differential voltages across the coils and generates an output signal which is peak detected by an operational amplifier (212) and supplied to a further operational amplifier (214) for comparison against a reference input from the filtered, half-wave rectified AC signal for generating an error signal output which is then divided down as a reference input to a further operational amplifier (216) and is also delayed by charging an RC timing circuit (R24 and C5) until the charge reaches a given value relative to the threshold provided by the divided down output error signal at the reference input of the last mentioned operational amplifier (216), whereupon the latter's output transitions and triggers a switch (218) with a latching relay (220). Reset circuitry, safety threshold circuitry, protective circuitry, normal operating mode testing circuitry, and improper field installation indicating circuitry are also disclosed.

Loading the Abstract Image...

First Claim