What Affects Current Sensing Accuracy? Understanding TCR in Precision Resistors for UK Applications

Why Temperature Matters in Current Sensing

In a current sensing circuit, resistance value is not the only parameter engineers need to consider. For electronic circuits that continuously monitor current, changes in operating temperature can affect resistance and, consequently, the sensing result. For this reason, temperature coefficient of resistance (TCR) is an important specification when selecting precision current sense resistors for UK electronic designs.

CSR Precision Current Sensing Resistors are designed for current sensing applications with low resistance, low inductance and a controlled temperature coefficient. According to the product specification, the CSR series has a TCR of 100ppm/°C and offers resistance tolerances down to 1%.

What Does 100ppm/°C Mean?

The temperature coefficient indicates how resistance changes as temperature changes. The CSR series specifies a TCR of 100ppm/°C, providing a direct reference for engineers evaluating the effect of temperature on resistance in current sensing circuits.

The series also provides 1%, 2% and 5% resistance tolerances. Where current measurement accuracy is more sensitive to the initial resistance value, the 1% option can be considered according to the circuit requirements. Rated power alone should not be used as the only selection criterion.

Low Resistance and Low Inductance

Current sensing applications generally use low resistance values to limit the electrical influence of the sensing element on the circuit. The CSR series provides resistance ranges of 5–25mΩ and 10–25mΩ, depending on the rated wattage.

The specified inductance is also below 10nH. For circuit designs where parasitic inductance needs to be considered, this specification can be evaluated together with resistance value, TCR and tolerance during component selection.

Selecting the Appropriate Power Rating

CSR resistors are available in 1W, 3W and 5W rated power versions. Engineers should select the appropriate rating based on actual current, resistance and operating temperature, rather than choosing a resistor solely from its resistance value.

The product documentation also specifies that when the ambient temperature exceeds 70°C, the rated power must be derated according to the supplied derating curve. Therefore, operating temperature should be considered during the design stage for equipment exposed to elevated ambient conditions.

Key Parameters for UK Current Sensing Resistor Selection

For UK electronic design engineers, selecting a precision current sensing resistor requires more than checking a single specification. Evaluating TCR, resistance tolerance, inductance, resistance range and rated power together provides a more practical basis for matching the resistor to the requirements of a specific current sensing circuit.