Today's electronic landscape is profoundly influenced by the precision in measuring thermistor performance—spanning both Positive Temperature Coefficient (PTC) and Negative Temperature Coefficient (NTC) varieties.
PTC Thermistor Testing Approach
Characterized by an increase in resistance with temperature hikes, starting with an initial temperature test and advancing to a thermal examination.
Initial Temperature Testing: Conducted under conditions mimicking an indoor climate, approximately 25°C, this stage initiates with deploying a multimeter, set to R×1, to gauge the thermistor's actual resistance at its terminals. The essence of this phase is the critical comparison of the measured resistance to the thermistor's stated nominal value, aiming for a deviation margin within ±2Ω. A notable discrepancy here could indicate compromised efficiency or damage.
Thermal Evaluation: Following the confirmation of standard operation at room temperature, a heat-based evaluation is undertaken. This involves the careful application of heat—possibly through a soldering iron—while closely observing resistance changes. A healthy thermistor will show a resistance increase that mirrors the temperature rise. A negligible change, however, hints at functional decline, rendering the device unsuitable for future applications. Here, maintaining a safe distance from the heat source to the thermistor is crucial to avoid damage due to overheating.
NTC Thermistor Detection Protocol
The NTC thermistor, exhibiting a decrease in resistance with temperature rise, demands an equally stringent examination through two main phases: assessing nominal resistance and determining the temperature coefficient.
Nominal Resistance Evaluation: This involves using a multimeter to measure the NTC thermistor's nominal resistance (Rt), ideally at around 25°C for accurate data. The procedure necessitates strict adherence to the defined measurement power and avoiding direct contact to prevent distortion from body heat.
Temperature Coefficient Determination: After measuring the initial room temperature resistance (Rt1), the thermistor is heated (for example, with an electric soldering iron) for a second resistance measurement (Rt2), while also recording the thermistor's surface temperature (t2) after heating. These data points are instrumental in calculating the thermistor's temperature coefficient (αt), further elucidating its performance characteristics.