How to use a multimeter to measure short circuit, open circuit, and short circuit of a circuit
Use the Ohm The greater the current flowing through the line. Use the 1k or 10k ohm level to measure both ends of the line. If the resistance is infinite, it means an open circuit.
Extended information:
The basic principle of a multimeter is to use a sensitive magnetoelectric DC ammeter (microampere) as the meter head.
When a small current passes through the meter, there will be a current indication. However, the meter head cannot pass large current, so some resistors must be connected in parallel or series with the meter head to shunt or reduce the voltage, so as to measure the current, voltage and resistance in the circuit.
The measurement process of a digital multimeter consists of a conversion circuit that converts the measured voltage signal into a DC voltage signal, and then an analog-to-digital (A/D) converter to convert the voltage analog quantity into a digital quantity, and then counts it through an electronic counter, and finally uses the measurement result in digital form. displayed directly on the display.
The function of measuring voltage, current and resistance of a multimeter is realized through the conversion circuit part, and the measurement of current and resistance is based on the measurement of voltage, which means that the digital multimeter is expanded on the basis of the digital DC voltmeter.
The A/D converter of the digital DC voltmeter converts the analog voltage that changes continuously with time into a digital quantity, and then the electronic counter counts the digital quantity to obtain the measurement result, and then the decoding display circuit displays the measurement result. The logic control circuit controls the coordinated work of the circuit and completes the entire measurement process in sequence under the action of the clock.
in principle:
1. The reading accuracy of the pointer meter is poor, but the process of the pointer swinging is relatively intuitive, and its swing speed can sometimes reflect the measured size more objectively (such as measuring the slight deviation of the TV data bus (SDL) when transmitting data). Jitter); the digital meter reading is intuitive, but the process of digital changes looks messy and not easy to watch.
2. There are generally two batteries in an analog watch, one with a low voltage of 1.5V, and one with a high voltage of 9V or 15V. The black test lead is the positive terminal relative to the red test lead. Digital meters commonly use a 6V or 9V battery. In the resistance mode, the output current of the test pen of the pointer meter is much larger than that of the digital meter. Using the R×1Ω gear can make the speaker make a loud "click" sound, and using the R×10kΩ gear can even light up the light-emitting diode (LED).
3. In the voltage range, the internal resistance of the pointer meter is smaller than that of the digital meter, and the measurement accuracy is relatively poor. In some high-voltage and micro-current situations, it is even impossible to measure accurately because the internal resistance will affect the circuit under test (for example, when measuring the acceleration stage voltage of a TV picture tube, the measured value will be much lower than the actual value). The internal resistance of the voltage range of the digital meter is very large, at least in the megohm level, and has little impact on the circuit under test. However, the extremely high output impedance makes it susceptible to the influence of induced voltage, and the measured data may be false in some situations with strong electromagnetic interference.
4. In short, pointer meters are suitable for measuring analog circuits with relatively large currents and high voltages, such as televisions and audio amplifiers. Digital meters are suitable for measuring digital circuits with low voltage and small current, such as BP machines, mobile phones, etc. It is not absolute. Pointer tables and digital tables can be selected according to the situation.
