Short circuit diagnostic tool
OwnerDennis A. Mitchellinventor
Life of this patent
Estimating the term…
Abstract
A device and method for diagnosing shorts and fault conditions in electrical circuits such as heating, ventilation, and air conditioning (HVAC) control circuits. The device includes a positive temperature coefficient (PTC) member to protect the electrical circuit from overcurrent conditions during diagnosis. The device also includes a light emitting diode (LED) and resistor electrically connected in parallel across the PTC member. An overcurrent condition causes the resistance of the PTC member to rise dramatically, creating a potential difference across the PTC member and lighting the LED. The invention also includes a method for locating a short in an HVAC control circuit using the short locating device.
Claims10
A diagnostic tool for detecting the presence of an electrical short in an electrical circuit having a voltage supply with a maximum output voltage, the tool comprising:
- a positive temperature coefficient (PTC) member that protects the electrical circuit being diagnosed from excessive current, the PTC member being characterized in that:
- the PTC member is in a relatively low resistance state when current flowing through the PTC member is substantially less than a trip current value;
- the PTC member's resistance increases nonlinearly to a relatively high resistance state when current flowing through the PTC member exceeds the trip current value;
- and
- the PTC member has two electrical leads;
- the PTC member is adapted to be damaged by an overvoltage condition of 120 volts;
- a signaling apparatus having two electrical leads electrically connected in parallel with the two electrical leads of the PTC member, wherein the signaling apparatus emits a signal only when the PTC member is in a relatively high resistance state;
- and
- two electrically conducting spring-biased clamps electrically connected to the electrical leads of the PTC member for temporarily connecting the diagnostic tool to the electrical circuit.
A diagnostic tool for detecting the presence of an overcurrent condition in an air conditioning control circuit, the tool comprising:
- impedance means for protecting the electrical circuit being diagnosed from excessive current, the impedance means being characterized in that:
- the impedance means is in a relatively low impedance state when current flowing through the impedance means is substantially less than a trip current value;
- the impedance means' impedance increases nonlinearly to a relatively high impedance state when current flowing through the impedance means exceeds the trip current value;
- and
- the impedance means is adapted to be damaged by an overvoltage condition of 120 volts;
- and
- signaling means electrically connected to the impedance means for signaling the presence of an overcurrent condition.
Dependencies are inferred from the claim text.