Question

The resistance of the thermistor is 5000 $\Omega$ at 20°C and its resistance temperature coefficient is 0.04°C. A measurement with a lead resistance of 10 $\Omega$ will cause an error of:

• A. 0.05°C
• B. 0.1°C
• C. 0.4°C
• D. 0.8°C

Hint:

Always account for lead resistance in precision measurements involving thermistors or other resistive temperature sensors to minimize errors.

Answer 1

The Correct Option is A

The error in temperature measurement due to the lead resistance can be calculated using the formula: \[ \text{Error} = \frac{R_{\text{lead}} \times \alpha \times T}{R_{\text{thermistor}}} \] Where:
- \(R_{\text{lead}} = 10 \, \Omega\) (lead resistance)
- \(\alpha = 0.04 \, \text{°C}^{-1}\) (temperature coefficient of resistance)
- \(R_{\text{thermistor}} = 5000 \, \Omega\) (thermistor resistance at 20°C)
- \(T = 20 \, \text{°C}\) (temperature)
Substituting the values: \[ \text{Error} = \frac{10 \times 0.04 \times 20}{5000} = 0.05 \, \text{°C} \] Therefore, the error caused by the lead resistance is 0.05°C.