Fuel cell stack coolant conductivity monitoring circuit
First Claim
1. A coolant contamination monitoring circuit for a fuel cell system comprising:
- a lamp operable in a non-illuminated state when a voltage build-up is less than a threshold value and an illuminated state when said voltage build-up is at least equal to said threshold value;
a first resistor connected between a first terminal of said lamp and a first conductive point in a coolant loop;
a second resistor connected between a second terminal of said lamp and a second conductive point in said coolant loop;
a photoresistor located adjacent to said lamp that varies in resistance in response to illumination of said lamp so as to function as a switch that is open when said lamp is not illuminated and that is closed when said lamp is illuminated; and
an optical isolator isolating said lamp and said photoresistor from ambient light.
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Accused Products
Abstract
The present invention provides a simple device that can be used to monitor the voltage potential between any two points within the fuel cell coolant system without loading (i.e. decreasing) the voltage being monitored. The monitoring circuit include a lamp electrically coupled to the coolant system and arranged in a light-tight package with a photoresistor. When the ionization voltage for the lamp is reached, a fully isolated signal is provided in the form of an abrupt resistance change in the photoresistor. Visual and audible indicators can be coupled to the monitoring circuit to indicate a coolant contamination condition.
29 Citations
20 Claims
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1. A coolant contamination monitoring circuit for a fuel cell system comprising:
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a lamp operable in a non-illuminated state when a voltage build-up is less than a threshold value and an illuminated state when said voltage build-up is at least equal to said threshold value;
a first resistor connected between a first terminal of said lamp and a first conductive point in a coolant loop;
a second resistor connected between a second terminal of said lamp and a second conductive point in said coolant loop;
a photoresistor located adjacent to said lamp that varies in resistance in response to illumination of said lamp so as to function as a switch that is open when said lamp is not illuminated and that is closed when said lamp is illuminated; and
an optical isolator isolating said lamp and said photoresistor from ambient light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A coolant contamination monitoring circuit for a fuel cell system comprising:
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a first lamp operable in a non-illuminated state when a voltage build-up is less than a first threshold value and an illuminated state when said voltage build-up is at least equal to said first threshold value;
a second lamp connected in series with said first lamp and operable in a non-illuminated state when said voltage build-up is less than a second threshold value and an illuminated state when said voltage build-up is at least equal to said second threshold value, wherein said second threshold value is greater than said first threshold value;
a first resistor connected in parallel with said second lamp;
a first monitoring resistor connected between a first terminal of said first lamp and a first conductive point in a coolant loop;
a second monitoring resistor connected between a first terminal of said second lamp and a second conductive point in said coolant loop;
a first and second photoresistor located adjacent to said first and second lamps, each photoresistor varying in resistance in response to illumination of an adjacent lamp so as to function as a switch that is open when said adjacent lamp is not illuminated and that is closed when said adjacent lamp is illuminated; and
optical isolators isolating said lamps and said photoresistors from ambient light. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification