Shunt resistors are connected in parallel with an instrument or component to divert electrical current. They provide an alternate path for current in case of failure, and can be used to accomplish a reduction in input sensitivity from the input line to ground. Current shunt resistors are low resistance, passive electronic devices used to measure alternating current (AC) or direct current (DC) by the voltage drop those currents create across the resistance. Electrical specifications for shunt resistors include ohms, resistance tolerance, current rating, power rating, temperature coefficient of resistance, and power coefficient of resistance. Ohms (O) measure a material’s opposition to the flow of electricity in a circuit. Temperature coefficient of resistance (TCR) refers to the change in resistance with change in temperature. Power coefficient of resistance (PCR) is the temperature rise caused by self-heating. For current-sensing shunts, resistances typically range from 100 µO to 500 mO. Low TCR and PCR are important. For shunt resistors used in current conversion applications, high precision may be required.
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