VCR (Voltage Coefficient of Resistance)
VCR is the formal datasheet abbreviation for voltage coefficient of resistance, the relative change in resistance per applied volt, given in ppm/V; it is the dominant linearity spec for high-voltage and HV-divider resistors.
Definition
VCR (voltage coefficient of resistance) is the practical name engineers and procurement teams reference on resistor datasheets. It is the same quantity as voltage coefficient — described and measured per IEC 60115-1 by applying 0.1 × rated and rated voltage and comparing the resistance values: VCR = (R_rated − R_low) / [R_low × (V_rated − V_low)] × 10⁶.
For wirewound and bulk-foil resistors VCR is below the resolution of most measurements (≤ 0.1 ppm/V). Thick-film parts typically fall between 10 – 100 ppm/V, and ordinary carbon composition can exceed 500 ppm/V at high voltage. Premium high-voltage thick-film series achieve ≤ 5 ppm/V through specially formulated ruthenium-oxide or bismuth-oxide pastes and grain-structure control.
Specifying low VCR is critical for HV measurement: a divider that ratios 100 kV down to 10 V for an oscilloscope or DVM must keep its ratio constant to better than 0.05 % across the operating voltage. Any VCR error scales directly with measurement error. In pulse-discharge applications VCR also affects the discharge waveform shape, distorting the apparent capacitance bank energy if not accounted for.
Related terms
Voltage Coefficient
Voltage coefficient is the change in resistance value per applied volt across the element, expressed in ppm/V; it captures the non-linear behaviour of resistive elements under high electric fields.
TCR (Temperature Coefficient of Resistance)
TCR is the relative change in resistance per degree Celsius of temperature change, expressed in parts per million per kelvin (ppm/K or ppm/°C); it determines how stable a resistor is over its operating temperature range.
Tolerance
The maximum allowable deviation of a resistor's actual resistance from its nominal value at room temperature and zero applied power, expressed as a percentage (e.g. ±1%, ±5%).
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