Simple test method of thermistor in air (1)

First, the purpose:

In the absence of special NTC thermistor test instruments, meters and measuring fixtures, but it is necessary to measure the NTC thermistor, this method provides a simple test method, although it cannot reach the professional level of accuracy, it can Roughly measure the resistance and accuracy of the thermistor.

2. Measuring tools and materials:

1. Four-and-a-half-digit multimeter: two pieces.

2. Test fixture: one.

3, ± 0.1 ℃ thermometer: one.

4. Stainless steel alligator clips: a pair.

3. Measurement methods and steps:

1. First, use the air conditioner to control the temperature of a room at 25±0.1℃.

2. Place the thermometer in the room to monitor the indoor temperature.

3. Connect a pair of alligator clips to the test terminals of a pair of multimeter pens respectively.

4. Clip the two lead ends of a standard thermistor to the alligator clip, insert the other end of the multimeter lead into the multimeter, turn on the multimeter and turn it to the appropriate gear for resistance measurement. At this time, the multimeter displays the resistance of the thermistor at this room temperature. value. (Note: The nominal resistance value accuracy is within ±0.1%, and the B value accuracy is ±1%)

5. Place the alligator clip near the thermometer. This multimeter is used to monitor the temperature change in the room.

6. When the display value of the multimeter monitoring the room temperature is relatively stable, it means that the room temperature is relatively stable. At this time, the resistance of the indoor constant temperature 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 value accuracy is the same, comparative measurement can be performed.

7. The thermistor to be tested can be judged as a qualified product according to the standard resistance value tested at room temperature ±5%.

Fourth, matters needing attention:

1. The indoor temperature change should be controlled within the range of 25±1℃. (Be sure to close the doors and windows during measurement to reduce air flow and avoid indoor personnel from entering and leaving and walking back and forth).

2. When the constant temperature cannot reach the control accuracy, the thermistor with the same resistance value accuracy can be used as the room temperature monitoring resistance for comparative measurement.

3. The two multimeters should be calibrated accurately before measurement, and at least the consistency of the two meters should be checked.

4. The constant temperature of the thermistor to be tested should not be less than 30 minutes at room temperature. If the product to be tested is energized and used, please place it for 12 hours before testing.

5. The thermometer, the thermistor for monitoring, and the resistance to be measured should be placed in the same position indoors to ensure the accuracy of the measurement.

6. When testing the thermistor, the operator should keep a certain distance between the thermistor in the hand of the operator to avoid measurement errors caused by human body temperature.





Simple test method of NTC thermistor in air (2)



First, the purpose:

In the absence of special NTC thermistor test instruments, meters and measuring fixtures, but it is necessary to measure the NTC thermistor, this method provides a simple test method, although it cannot reach the professional level of accuracy, it can Roughly measure the resistance and accuracy of the thermistor.

2. Measuring tools and materials:

1. Four-and-a-half-digit multimeter: two pieces.

2. One constant temperature oil pan: the size (500×300×100) can be customized, but it should not be too small.

3, 0.1 ℃ precision thermometer.

4. A pair of stainless steel alligator clips.

5. Appropriate amount of salad oil (limited to full oil pan).

3. Measurement methods and steps:

1. Fill the thermostatic oil pan with salad oil. (Note: If using a stainless steel plate, please place a 3~5mm plastic plate on the bottom of the plate for thermal insulation).

2. Put the thermometer horizontally into the oil pan, (the thermometer should be fully immersed in the oil), and the scale is upward.

3. Connect a pair of alligator clips to the test terminals of a pair of multimeter pens respectively.

4. Clip the two lead ends of a standard thermistor to the alligator clip, insert the other end of the multimeter lead into the multimeter, turn on the multimeter and turn it to the appropriate gear for resistance measurement. At this time, the multimeter displays the resistance of the thermistor at this room temperature. value. (Note: The nominal resistance value accuracy is within ±0.1%, and the B value accuracy is ±1%)

5. Put the alligator clip into the oil pan filled with salad oil, so that the alligator clip and thermistor are all immersed in the oil. This multimeter is used to monitor the temperature change of the oil in the oil pan.

6. When the display value of the multimeter monitoring the oil temperature is relatively stable, it means that the oil temperature is relatively stable. At this time, the resistance of the constant temperature in the oil can be tested, such as the resistance value and accuracy of the thermistor used for monitoring on the alligator clip and the heat to be measured. When the resistance value accuracy of the varistor is the same, the comparative measurement can be carried out.

Fourth, matters needing attention:

1. The temperature change of the oil in the oil pan should be controlled within the range of 25±3℃. (Be sure to close the doors and windows during measurement to reduce air flow and avoid indoor personnel from entering and leaving and walking back and forth).

2. When the constant temperature cannot reach the control accuracy, the thermistor with the same resistance value and accuracy can be used as the oil temperature monitoring resistor for comparative measurement.

3. The two multimeters should be calibrated accurately before measurement, and at least the consistency of the two meters should be checked.

4. The constant temperature of the thermistor to be tested in the oil should not be less than 2 minutes, and all should be immersed in the oil.

5. The temperature probe, the thermistor for monitoring and the resistance to be measured should be placed in the same position in the oil pan to ensure the accuracy of the measurement.