Method of measuring UPS power supply 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 very important. However, it cannot be measured directly with the frequency block of the digital multimeter, because the voltage that the frequency block can withstand is very low. Only a few volts. At this time, a 220V/6V or 220V/4V step-down transformer can be connected to the output terminal of the UPS power supply to reduce the voltage without changing the frequency of the power supply, and 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 still needs to be operated in the correct way. You can’t use them blindly without understanding the principles and functions. Reasonable operation according to the correct method is also conducive to better use of digital multimeters and prolongs the life of the instrument. life.
Frequency is the number of cycles a signal completes per second. Some digital multimeters can be measured, such as the FT215 digital multimeter to measure 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 enable and disable the frequency measurement function. Frequency measurements are only available for AC. When measuring frequency, the analog pointer display and range display can indicate the current AC voltage or current. Use the manual range function to incrementally select lower ranges to obtain stable readings.
How to use multimeter to measure short circuit
Pathway: There is a certain resistance. There is a beep. Short circuit: resistance is zero. There is a beep. Open circuit: infinite resistance. No beeps.
What file should the digital multimeter use to test whether there is a short circuit? How to identify whether there is a short circuit?
Adjust the digital multimeter to electric resistance (small range), and the displayed number is zero short circuit, if it is not zero, there is no short circuit, use R1 electric resistance, if the display resistance is zero, it is a short circuit.
How does a digital multimeter measure weak current circuit short circuit, open circuit, grounding, how to insert the meter wire, and how to adjust the gear position?
One: In the case of power failure, measure the ohm gear, the red and black test leads measure the live wire and the ground wire, and the ammeter becomes low resistance, which is a short circuit.
Two: In the case of power on, measure the voltage block, the red and black test leads measure the live wire and the ground wire, and the ammeter becomes zero voltage, which is an open circuit.
Three: In the case of electrification, measure the voltage block, and the red and black test leads measure the live wire and the ground wire. If the ammeter has voltage, it is grounded. The meter has no voltage, so it is not grounded.
How to measure short circuit
Turn off the power first, adjust the function switch of the multimeter to the buzzer position, put the two pens of the multimeter on the two terminals to be tested, if there is a short circuit, there will be a buzzer, and a small conduction voltage value will be displayed, at this time There is a short circuit between the two measured points.
operating procedures
1. Before use, you should be familiar with the functions of the multimeter, and correctly select the gear, range and test lead jack according to the object to be measured.
2. When the size of the measured data is unknown, the range switch should be set to the maximum value first, and then switch from the large range to the small range, so that the indicator pointer of the instrument is above 1/2 of the full scale.
3. When measuring resistance, after selecting the appropriate magnification, touch the two test leads so that the pointer points to the zero position. If the pointer deviates from the zero position, adjust the "zero adjustment" knob to make the pointer return to zero to ensure accurate measurement results. . If it cannot be adjusted to zero or the digital display meter sends out a low voltage alarm, it should be checked in time.
4. When measuring the resistance of a certain circuit, the power supply of the circuit under test must be cut off, and live measurement is not allowed.
5. When using a multimeter for measurement, pay attention to the safety of the person and the instrument. Do not touch the metal part of the test pen with your hands during the test. It is not allowed to switch the gear switch with power on to ensure accurate measurement and avoid electric shock and burnout of the instrument. ACCIDENT.
