How to measure UPS power frequency with digital multimeter
For UPS power supply. The stability of the voltage at its output terminal is an important parameter, and the frequency of its output is also important. However, you cannot directly use the frequency block of a digital multimeter to measure because the voltage that the frequency block can withstand is very low. Only a few volts. At this time, you can connect a 220V/6V or 220V/4V step-down transformer to the output end of the UPS power supply to reduce the voltage without changing the frequency of the power supply. Then connect the frequency block to the output of the transformer to measure the UPS power supply. Frequency of.
In general, the use of digital multimeters must be operated in the correct way. You cannot use it blindly without understanding the principles and functions. Reasonable and correct operation will also help the digital multimeter to be better used by us and extend the life of the instrument. life.
Frequency is the number of cycles a signal completes per second. Some digital multimeters can measure, such as the FT215 digital multimeter, which measures the frequency of a signal by counting the number of intersections between the measured signal and the trigger level per second. The trigger level of all ranges is the same as the COM terminal level. Under the AC measurement function, press the SHIFT key to start and stop the frequency measurement function. Frequency measurements are for AC only. When measuring frequency, the analog pointer display and range display indicate the current AC voltage or current. Use the manual range function to progressively select lower ranges to obtain stable readings.
How to measure the quality of electric water heater temperature sensor with multimeter
Temperature sensor for electric water heater.
The temperature sensor used in electric water heaters is generally a thermistor with a negative temperature coefficient. The resistance will decrease as the temperature increases. Its nominal value is measured at 25°C. This temperature sensor has a variety of nominal values, such as 10KΩ, 20KΩ, and 50KΩ. When measuring the quality of the electric water heater temperature sensor, adjust the digital multimeter to the appropriate resistance range according to its nominal value, and use the red and black test leads of the multimeter to touch the metal sheet of the plug respectively (see the picture above). At this time, the multimeter should display Have a suitable resistance value (not very different from the nominal value), and then pinch the metal part of the sensor with your hand. If there is a certain change in the resistance value, it means that the sensor is basically good.
Digital multimeter.
During measurement, if the resistance value displayed by the multimeter is very small or infinite, it means there is a problem with the sensor. At this time, you can check whether the sensor plug is broken or connected. If the plug is good, then the only way is to replace the temperature sensor with the same specification. .
