Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1995-08-31
1997-05-20
Regan, Maura K.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
73 6144, 324663, G01R 2726
Patent
active
056315686
ABSTRACT:
An apparatus for determining the remaining life of hydraulic fluid in a hydraulic system having a hydraulic container includes a capacitor formed by a pair of electrodes. A charging circuit produces a charging current of constant magnitude. The charging current is used to charge the capacitor to a predetermined voltage. A timing circuit measures the elapsed time between the time at which the charging circuit begins to produce the charging current and the time at which the capacitor has been charged to the predetermined voltage. The timing circuit also produces a pulse width modulated signal. The magnitude of the pulse width modulated signal is indicative of the time difference. A controller receives the pulse width modulated signal and determines the life of the hydraulic fluid.
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SAE Technical Paper Series--910497 Feb. 25-Mar. 1, 1991 "A Capacitive Oil Deterioration Sensor".
Codina George
Murr Donna J.
Ramamoorthy Chandrasekar
Caterpillar Inc.
Regan Maura K.
Yee James R.
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