How to judge the temperature sensor with a multimeter
Nowadays, electric water heater into the ordinary people's families, has become one of the main household appliances. The temperature sensor of the water heater is the main measurement sensor to obtain the heated medium water, temperature sensor damage, it is unable to accurately and timely access to the temperature of the measured medium water heating, so that the electric water heater can not accurately control the temperature.
In the electric water heater with the temperature sensor mainly thermistor temperature sensor and platinum RTD temperature sensor, their output to the secondary instrumentation thermostat are resistance signals. One of the electric water heater is generally used thermistor negative temperature coefficient of the thermistor temperature sensor, as the temperature rises its output resistance becomes smaller. And platinum thermistor as the temperature rises its output resistance becomes larger.
Multimeter measurement NTC thermistor good or bad
Place the temperature sensor of the water heater at room temperature. Connect the two pens of the digital multimeter to the two pins of the thermistor, and measure its actual blocking. Then the measured actual block and the nominal resistance value comparison, if the actual resistance value and the nominal resistance value difference ± 2 ohms is considered normal. On the contrary, thermistor temperature sensor performance deterioration or even damage. Can also be thermistor te
mperature detection, heating with a lighter, the resistance of the multimeter is with the temperature and become smaller, indicating that the thermistor temperature sensor is normal, the resistance did not change, indicating that the thermistor temperature sensor is damaged.
Measure the platinum thermistor temperature sensor with a multimeter.
As the platinum RTD temperature sensor has three lead wires, to find out which one of the different colours, one of the pens with a multimeter connected to the immobility. Another pen were hit to connect the additional two leads. Resistance value measured separately, if the two two measurements found after the resistance value of infinity or less than 100 ohms, indicating that the platinum RTD damage. If the two measurements after the resistance value is not the same, that the platinum RTD compensation line or its lead line there are problems. At the same time you can give the platinum RTD manual heating, if the resistance value does not change that the platinum RTD is damaged. If the measured actual resistance value and the nominal resistance value of the difference is large, indicating that the performance of platinum RTD in the deterioration.
