Trouble detecting circuit for resistive sensor type indicator
First Claim
1. A trouble detecting circuit for a resistive-sensor type indicator having a resistive sensor whose resistance changes according to a quantity to be measured and an indicator for indicating a sensor output voltage developed across the resistive sensor, which comprises:
- (a) means for comparing the sensor output voltage with a reference voltage and outputting a first signal indicative of a normal resistive sensor when the reference voltage exceeds the sensor output voltage and a second signal indicative of an abnormal resistive sensor when the sensor output voltage exceeds the reference voltage; and
(b) means for controlling the sensor output voltage of said resistive sensor in such a way that said resistive sensor is connected to said indicator in response to the first signal to directly indicate a quantity to be measured on said indicator and to a substantially ground level in response to the second signal to indicate a minimum quantity on said indicator when said resistive sensor is in trouble.
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Accused Products
Abstract
In a resistive-sensor type indicator having a resistive sensor whose resistance changes according to a quantity to be measured and an indicator for indicating a sensor output voltage developed across the resistive sensor, when the resistive sensor is open due to disconnection or malconnection of the resistive sensor, the indicator indicates a maximum reading, thus resulting in a problem such that the user cannot recognize the abnormal state. To overcome this problem, a novel trouble detecting circuit is additionally incorporated in the indicator. The circuit comprises a comparator for outputting an abnormal signal when the sensor voltage exceeds a reference voltage and a transistor for grounding the resistive sensor in response to the abnormal signal. Therefore, the indicator indicates a minimum reading in case of resistive sensor trouble.
18 Citations
6 Claims
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1. A trouble detecting circuit for a resistive-sensor type indicator having a resistive sensor whose resistance changes according to a quantity to be measured and an indicator for indicating a sensor output voltage developed across the resistive sensor, which comprises:
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(a) means for comparing the sensor output voltage with a reference voltage and outputting a first signal indicative of a normal resistive sensor when the reference voltage exceeds the sensor output voltage and a second signal indicative of an abnormal resistive sensor when the sensor output voltage exceeds the reference voltage; and (b) means for controlling the sensor output voltage of said resistive sensor in such a way that said resistive sensor is connected to said indicator in response to the first signal to directly indicate a quantity to be measured on said indicator and to a substantially ground level in response to the second signal to indicate a minimum quantity on said indicator when said resistive sensor is in trouble. - View Dependent Claims (2, 3, 4)
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5. A trouble-detecting circuit for a resistive-sensor type indicator having a resistive sensor whose resistance changes according to a quantity to be measured and an indicator for indicating a sensor output voltage developed across the resistive sensor, which comprises:
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(a) an operational amplifier having a first input terminal connected to said resistive sensor and a second input terminal connected to a reference voltage, for outputting a normal signal when the reference voltage exceeds the sensor output voltage and an abnormal signal when the sensor output voltage exceeds the reference voltage; and (b) a transistor, connected between said operational amplifier and the indicator, turned off in response to the normal signal to directly indicate a quantity to be measured on said indicator to indicate a ground voltage level when said resistive sensor is in trouble.
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6. A trouble detecting circuit for a resistive-sensor type indicator having a resistive sensor whose resistance changes according to a quantity to be measured and an indicator for indicating a sensor output voltage developed across the resistive sensor, which comprises:
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(a) a Zener diode having a cathode electrode connected to said resistive sensor, for outputting a normal signal when a reference Zener voltage exceeds the sensor output voltage and an abnormal signal when the sensor output voltage exceeds the reference Zener voltage; and (b) a transistor, connected between said operational amplifier and the indicator, turned of in response to the normal signal to directly indicate a quantity to be measured on said indicator and turned on in response to the abnormal signal to indicate a ground voltage level when said resistive sensor is in trouble.
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Specification