Use of digital voltmeter

Abstract: The information on the use of digital voltmeters is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. The so-called voltage-frequency conversion type refers to converting the measured voltage value into a frequency value during measurement, and then using a frequency meter to display the recalcitrance value, which can reflect the size of the voltage value. This kind of meter is also called V-F type. Figure 14-41 is the principle block diagram of V-F type digital voltmeter. Since you can. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following are the details of the article on the use of digital voltmeters. The so-called voltage-frequency conversion type refers to converting the measured voltage value into a frequency value during measurement, and then using a frequency meter to display the recalcitrance value, which can reflect the size of the voltage value. This kind of meter is also called V-F type. Figure 14-41 is the principle block diagram of V-F type digital voltmeter. Since the frequency of the controlled frequency oscillator can be directly controlled by the measured voltage, why not directly measure the frequency value of the controlled frequency oscillator as the corresponding measured voltage value, but use the mixing method? It turns out that the main purpose of using frequency mixing is to increase the range of output frequency variation, and to obtain zero point 0 because, generally, the frequency of the controllable frequency oscillator is changed by changing the capacitance C of the varactor. It is known that the oscillator frequency changes when When the capacitance tube is controllable, its capacitance value can vary within a certain range. There are many types and types of digital voltmeters. Figure 14-42 shows the structure diagram of the front and rear panels of the PZ26 digital voltmeter. The PZ26 digital voltmeter adopts a large-scale integrated circuit and a 3H-bit double integral A-D. Converter, its small size, light weight, easy to carry. 1) Range. 2) Display. The maximum displayed value is±In 1999, the polarity and decimal point can be automatically displayed. When the input signal exceeds the range, the first digit will flash, indicating overload. 3) Sampling speed. The sampling speed is 2~3 times/s, and the integration time of the measured voltage is 80ms for each measurement. 4) The effect of temperature on the error. When the operating temperature is (20±5) 1. When the relative humidity is below 80%, the error of the voltmeter can be guaranteed within 30 days of use. When used within 30 to 90 days, an additional error of 0.2% should be added. 5) The ability to suppress series mode interference. yes (50±1) The power frequency and harmonic suppression capability of Hz shall be greater than 30dB, but the peak value of the interference electric M shall not exceed the range. 6) Common mode interference suppression capability. When the input terminal has a maximum imbalance of 1k, and the common mode interference DC voltage or power frequency voltage is not greater than 250V, the suppression capability is greater than 60dB. 7) Overload capability. In the 1000V range, the overload is allowed to be 10%, the 600V range is allowed to be overloaded by 50%, and the remaining 60V, 6V, 600mV, 60mV are allowed to exceed 10 times. During the measurement, the maximum working voltage of end-to-ground shall not exceed 250V. 14.4.3 Precautions when using the PZ26 digital voltmeter 1) The surrounding environment should be free from strong electromagnetic field interference, corrosive gases or impurities, and the meter’s heat dissipation holes should not be shielded and well ventilated. 2) The power wiring should be correct, red is the phase wire, black is the ground wire, and green is the neutral wire. 3) Before turning on the power, set the range selection knob to zero, then turn on the power and preheat for 40 minutes. If it has not been used for a long time or it is used for the first time, it should be preheated for 1~2 hours and then adjusted to zero. 4) Set the range selection knob to '‘calibration”, pre-adjust and self-calibrate the digital voltmeter. 5) During the measurement, if the first digit flickers, it means that the input voltage under test is overloaded, and the range should be changed. 1. Training tools, instruments and equipment clamp ammeter, three-phase cage motor, copper core insulated flexible wire, common tools. 2. Training objectives 1) Learn to use the clamp ammeter correctly. 2) Master the direct measurement of line current with a clamp ammeter. 3. Training content 1) According to the regulations of the motor nameplate, connect the connecting piece in the junction box. 2) Connect to the three-phase AC circuit according to the regulations, and make it energized and run. 3) Use a clamp-type ammeter to detect the instantaneous starting current and the no-load current after the speed reaches the rated value, and record the relevant measurement data. 4) After the wire is wound twice in the jaw, measure the no-load current and record the relevant measurement data. 5) When the motor is running with no load, artificially disconnect one-phase power supply, such as removing a certain phase fuse, use a clamp-type ammeter to detect the open-phase running current (the detection time is as short as possible), turn off the power supply immediately after the measurement, and record it. about measurement data. 6) Fill in the training report The above is the whole content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'Use of Digital Voltmeter'

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