Dual magnetic coil driver and monitor sensor circuit

In a transducer having a delta coil for generating a magnetic flux path through a path of movement of a magnetically permeable member, such that movement of said member changes the return coupled flux linkage, which flux change indicates movement of said member, and having a reference coil spaced sufficiently from said path of movement of said member such that movement of the latter has less affect on return coupled flux linkage of said reference coil than said delta coil, a sensor circuit comprising:

• means connecting said coils in parallel;
• means applying electrical potential across said parallel coils;
• error amplifier means having a reference input from said reference coil and a comparing input from said delta coil, and having an output, such that when said magnetically permeable member moves in a given direction the voltage at said comparing input of said amplifier means increases in a given polarity direction above a given threshold relative to the voltage at said reference input of said amplifier means such that said output of said amplifier means increases and provides an output error signal;
• timing means connected to said output of said amplifier means and delaying said output error signal;
• and
• switch means connected to said timing means and actuated by said delayed output error signal to provide a designated switching function.

In a transducer having a delta coil for generating a magnetic flux through a path of movement of a magnetically permeable member, such that movement of said member changes the return coupled flux linkage, which flux change indicates movement of said member, and having a reference coil spaced sufficiently from said path of movement of said member such that movement of the latter has less affect on return coupled flux linkage of said reference coil than said delta coil, a sensor circuit comprising:

• power supply means supplying a regulated DC signal and supplying an AC signal;
• means connecting said coils in respective parallel voltage dividers;
• diode means half-wave rectifying said AC signal and supplying same to said parallel voltage dividers with no phase shift between said coils;
• differential amplifier means having a reference input from said reference coil and a comparing input from said delta coil, and having an output, such that when said magnetically permeable member moves in a given direction the voltage at said comparing input of said differential amplifier means increases in a given polarity direction above a given threshold relative to the voltage at said reference input of said differential amplifier means such that said output of said differential amplifier means provides an output signal;
• first operational amplifier means having a reference input connected to said diode means and supplied with said half-wave rectified AC signal, and having a comparing input connected to said output of said differential amplifier means, and having an output, such that when the voltage at said input of said first operational amplifier means from said output of said differential amplifier means increases in a given polarity direction above a given threshold value relative to the half-wave rectified AC signal voltage at said reference input of said first operational amplifier means, the output of said first operational amplifier means transitions and provides an output error signal, said half-wave rectified AC signal voltage from said diode means providing a dynamic floating reference at said reference input of said first operational amplifier means;
• timing means comprising an RC timing circuit having a resistor and capacitor connected to said output of said first operational amplifier means and delaying said output error signal;
• second operational amplifier means having a reference input connected to said output of said first operational amplifier means, and having a comparing input connected by said RC timing circuit to said output of said first operational amplifier means, and having an output, such that said output of said second operational amplifier means transitions when the voltage at said comparing input of said second operational amplifier means increases in a given polarity direction as said output error signal from said output of said first operational amplifier means charges said capacitor of said RC timing circuit above a given threshold value relative to the voltage at said reference input of said second operational amplifier means provided by said output error signal from said output of said first operational amplifier means;
• switch means connected to said output of said second operational amplifier means and actuated thereby to provide a designated switching function.

Oil pressure sensor circuitry for an oil pressure sensor directly mounted to a lubrication pump and directly inserted into and across the high and low pressure sides of said pump to sense differential pump pressure, said sensor comprising a sensor body having a first portion disposed internally within said pump to be exposed to the internal pump environment, and a second portion extending externally of said pump, a magnetically permeable piston axially slideable within said first internal sensor body portion, a low pressure port in said first internal sensor body portion communicating with said low pressure side of said pump to apply pressure from the latter to one axial end of said piston, a high pressure port in said first internal sensor body portion communicating with said high pressure side of said pump to apply pressure from the latter to the other axial end of said piston, a delta coil mounted in said body for generating a magnetic flux path including portions extending into the path of movement of said piston such that said piston movement changes the return coupled flux linkage, which flux change indicates piston movement according to said pressure differential, a reference coil mounted in said body adjacent said delta coil and on the opposite side thereof from said piston such that movement of said piston has less affect on returned coupled flux linkage of said reference coil than said delta coil, said lubrication pump having a pump motor, said sensor circuitry comprising:

• power supply means supplying a regulated DC signal and supplying an AC signal;
• means connecting said coils in respective parallel voltage dividers;
• diode means half-wave rectifying said AC signal and supplying same to said parallel voltage dividers;
• differential amplifier means having a reference input from said reference coil and a comparing input from said delta coil, and having an output, such that when said piston moves in a given direction the voltage at said comparing input of said differential amplifier means increases in a given polarity direction above a given threshold relative to the voltage at said reference input of said differential amplifier means such that said output of said differential amplifier means orovides an output signal;
• first operational amplifier means having a reference input connected to said diode means and supplied with said half-wave rectified AC signal, and having a comparing input connected to said output of said differential amplifier means, and having an output, such that when the voltage at said comparing of said first operational amplifier means from said output of said differential amplifier means increases in a given polarity direction above a given threshold value relative to the half-wave rectified AC signal voltage at said reference input of said first operational amplifier means, the output of said first operational amplifier means transitions and provides an output error signal, said half-wave rectified AC signal voltage from said diode means providing a dynamic floating reference at said reference input of said first operational amplifier means;
• timing means comprising an RC timing circuit having a resistor and capacitor connected to said output of said first operational amplifier means and delaying said output error signal;
• second operational amplifier means having a reference input connected to said output of said first operational amplifier means, and having a comparing input connected by said RC timing circuit to said output of said first operational amplifier means, and having an output, such that said output of said second operational amplifier means transitions when the voltage at said comparing input of said second operational amplifier means increases in a given polarity direction as said output error signal from said output of said first operational amplifier means charges said capacitor of said RC timing circuit above a given threshold value relative to the voltage at said reference input of said second operational amplifier means provided by said output error signal from said output of said first operational amplifier means;
• switch means connected to said output of said second operational amplifier means and actuated thereby to turn off said pump motor, said switch means including a second charging capacitor charged by said regulated DC signal, a latching relay having a set coil connected to said second capacitor, a semiconductor switch having a pair of main terminals connected in series with said set coil, said semiconductor switch having a control terminal connected to said output of said second operational amplifier means such that said transitioning of the latter drives said semiconductor switch into conduction to complete a current path therethrough and discharge said second capacitor through said set coil to actuate said relay to a first condition, and wherein said relay has a reset coil connected to said first mentioned capacitor, and comprising a second semiconductor switch having a pair of main terminals connected in series with said reset coil and having a control terminal controlled by a manual user-operated reset switch connected in a reset circuit with said regulated DC signal for biasing said second semiconductor switch into conduction to complete a current path between said main terminals of said second semiconductor switch and discharge said first capacitor through said reset coil to resettingly actuate said relay to an alternate condition;
• a safety threshold circuit supplying said regulated DC signal to said reference input of said second operational amplifier means to provide a minimum threshold for said comparing input of said second operational amplifier means regardless of the condition of said output error signal from said output of said first operational amplifier means to prevent false actuation of said relay.