What are the ways to measure thermistors?

1. Clamp the two lead ends of a standard thermistor on the crocodile clip, insert the other end of the multimeter pen into the multimeter, turn on the multimeter and dial it to the appropriate gear for resistance measurement, and the multimeter will show the resistance value of the thermistor at room temperature.

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

3. Fill the thermostatic oil pan with salad oil. (Note: If you use a stainless steel plate, please put a 3 5mm plastic plate on the bottom of the plate as a thermal insulation layer).

4. When the multimeter display value of monitoring oil temperature is relatively stable, it indicates that the oil temperature is relatively stable, and 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 crocodile clip are the same as the resistance accuracy of the thermistor to be measured, and the comparison measurement can be carried out.

5. Replace a pair of crocodile clips on a pair of multimeter pen test ends.

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

It is worth noting that when the constant temperature cannot reach the control accuracy, the thermistor with the same resistance accuracy can be used as the oil temperature monitoring resistance for comparative measurement. The temperature change of the oil in the oil pan should be controlled within the range of 25 3. The temperature probe, the thermistor for monitoring, and the resistor to be measured should be placed in the same position in the oil pan to ensure the accuracy of the measurement.

The two multimeters should be calibrated accurately before measurement, and at least the consistency of the two meters should be checked. The constant temperature of the thermistor to be tested in oil should not be less than 2 minutes, and it should be fully immersed in oil.

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A thermistor is a type of sensor resistance whose resistance value changes with temperature. There are four steps to measure the quality of a thermistor, and here's how:

1. Measure the resistance value at room temperature, put the multimeter in a suitable ohmic stop, use two meter pens to contact the two pins of the thermistor respectively to measure the actual resistance, and compare it with the nominal resistance value, if the difference between the two is too large, it means that the measured thermistor has poor performance or has been damaged.

2. Measure the resistance value when the temperature changes. On the basis of normal room temperature test, the temperature rise or cooling test can be carried out.

3. Pinch the thermistor with your hand to measure the resistance value, observe the universal representation, and then you will see that the displayed data changes with the increase of temperature, indicating that the resistance value is gradually changing.

4. When the resistance value changes to a certain value, the display data will gradually stabilize. If the ambient temperature is close to body temperature during measurement, the soldering iron can be heated close to or close to the thermistor.

Maintenance is the way to reduce damage to thermistors:

When the part of the thermistor that comes into contact with the surface of the hot roller is blocked by dirt, the temperature of the fuser roller increases and the preheating time increases. If not cleaned in time, the working temperature will increase with the thickening of the dirt, and when the temperature of the fixer exceeds 196 degrees Celsius, the temperature insurance will be blown off, so regular cleaning of the thermistor is an important part of maintenance.

1. Use a multimeter.

Measure the resistance of three wires, and short the two wires with a resistance of 0.

In fact, it is a small resistance value, which is the line resistance, which is used to eliminate the influence of the line resistance on the measured value), and the other wire is connected to the other end of the measuring instrument.

2. Thermal resistance.

Three-wire connection method is adopted. The three-wire system is used to eliminate measurement errors caused by the resistance of the connected wires. This is because the circuit used to measure RTD is generally an unbalanced bridge.

Resistance inHot statewithRoom temperatureIn order to measure the resistance value of thermal resistance, the resistance value of the thermoelectric resistance needs to be tested in accordance with different temperature environments, the resistance has a positive temperature coefficient and a negative temperature coefficient, and some of the resistance materials change nonlinearly with temperature. By Ohm's law r=u i, it is also possible to calculate the resistance at this temperature.

1. In thermal resistance.

In the junction box, the three connecting wires are all disassembled, and the resistance value of the RTD element is measured separately, such as PT100 RTD in 25 environment, the resistance value of A, B or A, C at both ends is generally about 110 ohms, and the resistance value at both ends of B and C is almost zero, indicating that the RTD element is normal.

2. When the resistance value of A, B or A and C is less than 100, there may be a local short circuit fault of the RTD element. The resistance values at a, b, or both ends of a, c, are infinite.

There may be an open circuit fault in the RTD element.

3. Suppose the single-wire resistance of the three-wire wiring method is 5 ohms, and the terminal is located.

The resistance value at both ends of A, B or A and C is about 120 ohms, and the resistance value at both ends of B and C is about 10 ohms, indicating that the three-wire wiring is correct.

4. Before measuring, the wiring of the A1, B1 and C1 ends of the AI card of the DCS system should be disassembled, and the temperature display can be judged by measuring the resistance value of the thermal resistance on the spot.

5. The RTD element is normal, measure the resistance at the terminal, the resistance value at both ends of A, B or A and C is infinite, and there may be an open circuit fault in the wire from the terminal to the on-site RTD. The resistance at both ends of A and B is normal, the resistance at both ends of A and C is very large, and the resistance at both ends of C and B is still very large, so it can be determined that the C line is open. B and C can be understood as a wire, and the resistance value is likely to be poor contact, and the resistance value is infinite.

Open-circuit faults. 6. The wiring of the RTD temperature measurement circuit increases the resistance value of the circuit due to oxidation, corrosion, loosening and other cavity reasons, so that the measured temperature is high or fluctuating, and only relies on the multimeter.

It is very difficult to measure the resistance to determine the above reasons. Only by comprehensive analysis, comparison, and elimination can it be possible to find the point of failure.

Third, the measured temperature value is estimated by the linearity of the measured resistance value and temperature:

For example, the resistance of a PT100 RTD at the junction box is 162 ohms, and the temperature measured by the closure estimation of the wire celery orange is roughly 161

What are the advantages and disadvantages of heat hunger finger resistors compared to thermal resistances? What problems do you have to pay attention to when using thermistors for linear temperature measurements?

Answer: Advantages: (1) The temperature coefficient of resistance is large, and the sensitivity is high, which is about 10 times that of thermal resistance; (2) The structure is simple, the volume is small, and the point temperature can be measured; (3) The resistivity is high, the thermal inertia is small, and it is suitable for dynamic measurement; (4) Easy to maintain and carry out long-distance control (5) Simple manufacturing and long service life.

The resistance value is large, and the influence of lead resistance can be ignored.

Disadvantages: poor interchangeability and serious nonlinearity. Poor stability.

When making linear temperature measurements, it should be noted that the temperature flowing through the thermistor should not be too large and should be within its rated range. Or you need to make a nonlinear correction first.

The temperature coefficient of resistance is large, and the sensitivity is high, about 10 times that of thermal resistance;

The structure is simple, the body culture fiber is small, and the point temperature can be measured;

High resistivity, small thermal inertia, suitable for dynamic measurement of slag failure;

Easy to maintain and control over long distances.

1. The thermistor has the characteristic of changing the resistance value with the change of temperature.

2. By measuring the resistance of the thermistor, the temperature can be measured.

Strictly speaking, almost all conductors and semiconductor materials have their own resistivity that changes under the influence of temperature! The most common of the various temperature sensing elements that take advantage of this characteristic is the thermistor!

The characteristic of thermistors is that their resistance changes with temperature! We convert this change in resistance into a change in current! It is displayed by the pointer or number after circuit processing! This completes the temperature measurement!