Detection of coolant contamination in lubricating fluids
First Claim
1. A method of monitoring the presence of engine coolant contamination in lubricant comprising:
- (a) disposing at least two electrodes in the lubricant and applying a relatively low voltage alternating current to one of said electrodes and sweeping the frequency of the voltage over a predetermined range;
(b) measuring the current and phase angle at a second of said electrodes at predetermined frequency intervals during the sweep and computing the reactance and resistance at each current measurement;
(c) determining the least value of reactance Z″
min from said computing;
(d) selecting a frequency fi, less than the frequency corresponding to Z″
min;
(e) exciting said one electrode with said voltage at the frequency fi and measuring the current and phase angle at said second electrode and computing the reactance Z″
i and the resistance Z′
i;
(f) determining the parameter where Δ
Z″
is the change in reactance (Z″
i−
Z″
min) and Δ
Z′
is the change in resistance (Z′
−
Z′
@Z″
min); and
,(g) providing an indication that coolant contamination exists when Θ
reaches a predetermined value.
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Accused Products
Abstract
An impedance spectroscopy technique and system for detecting in real time engine coolant contamination in lubricant. A probe is disposed in the lubricant and the probe excited with an a.c. voltage frequency sweep over a selected frequency range. The current and current phase angle are measured at selected frequency intervals and the reactance and resistance computed and plotted at each frequency internal as Nyquist plots. The Nyquist minimum is determined at various lubricant temperatures and a database compiled. The probe is then excited in-situ and current measurements taken for a selected frequency lower than the Nyquist minimum to insure measurement of electrode surfaces characteristics. The reactance and resistance are then computed and the angle Θ of change (slope) of reactance with respect to resistance computed. The value of Θ is then compared with values of contamination concentration Ψ versus Θ in a database, and the value of Ψ determined by interpolation.
33 Citations
9 Claims
-
1. A method of monitoring the presence of engine coolant contamination in lubricant comprising:
-
(a) disposing at least two electrodes in the lubricant and applying a relatively low voltage alternating current to one of said electrodes and sweeping the frequency of the voltage over a predetermined range; (b) measuring the current and phase angle at a second of said electrodes at predetermined frequency intervals during the sweep and computing the reactance and resistance at each current measurement; (c) determining the least value of reactance Z″
min from said computing;(d) selecting a frequency fi, less than the frequency corresponding to Z″
min;(e) exciting said one electrode with said voltage at the frequency fi and measuring the current and phase angle at said second electrode and computing the reactance Z″
i and the resistance Z′
i;(f) determining the parameter where Δ
Z″
is the change in reactance (Z″
i−
Z″
min) and Δ
Z′
is the change in resistance (Z′
−
Z′
@Z″
min); and
,(g) providing an indication that coolant contamination exists when Θ
reaches a predetermined value.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
Specification