Test method for NTC thermistor in air

In the absence of dedicated NTC thermistor test instruments, meters and measurement fixtures, but need to measure NTC thermistors, how to measure? Here's a simple test method:

1. Measurement tools and materials:

(1) Four and a half multimeters: two

(2) Test fixture: one

(3) ± 0.1 ° C thermometer: one

(4) Stainless steel alligator clip: a pair

2. Measurement methods and steps:

(1) First, use a air conditioner to control the temperature of a room at 25 ± 0.1 ° C;

(2) Place the thermometer in the room to monitor the indoor temperature;

(3) replacing a pair of alligator clips on the test end of a pair of multimeter pens;

(4) Clip the two lead ends of a standard varistor on the alligator clip, insert the multimeter into the multimeter at the other end, turn on the multimeter and dial it to the resistance to measure the appropriate gear. At this time, the multimeter shows the thermistor at room temperature. Resistance value; (Note: the nominal resistance accuracy is within plus or minus one percent, and the B value accuracy is plus or minus one percent)

(5) Place the alligator clip near the thermometer, this multimeter is used to monitor the temperature change in the room;

(6) When the monitored room temperature multimeter display value is relatively stable, it indicates that the room temperature is stable. At this time, the indoor constant temperature resistance can be tested, such as the resistance value and accuracy of the thermistor used for monitoring on the alligator clip and the thermistor to be tested. When the resistance values are the same, the comparison measurement can be performed;

(7) The thermistor to be tested can be judged according to the range of positive and negative five percent of the standard resistance value tested at room temperature;

3. Note:

(1) The temperature change in the room should be controlled within the range of 25 ± 1 °C. (Be sure to close the doors and windows when measuring, reduce air flow, avoid indoor personnel entering and leaving and moving back and forth);

(2) When the constant temperature does not reach the control accuracy, the same resistance precision thermistor can be used as the room temperature monitoring resistor for comparative measurement;

(3) Two multimeters should be verified accurately before measurement, and at least the consistency check of the two tables should be performed;

(4) The temperature of the thermistor to be tested should not be less than 30 minutes at room temperature. If the product to be tested is used after being energized, please leave it for 12 hours before testing.

(5) The thermometer, the thermistor for monitoring, and the resistance to be tested should be placed in the same position indoors to ensure accurate measurement;

(6) When testing the thermistor, the operator's hand should keep the distance between the varistor as far as possible to avoid the measurement error caused by human body temperature.