Multimeter Purchase Guide and Operating Standards
Selection criteria
1. The reading precision of the pointer table is not high, but the whole process of pointer shaking is more visualized, and its shaking speed can sometimes reflect the measured size more objectively (for example, the measurement of TV data bus (SDL) in Slight jitter when transmitting data); digital meter readings are visualized, but the process of digital transformation looks messy and not easy to watch.
2. There are usually two batteries in the pointer watch, one is low voltage 1.5V, the other is high voltage 9V or 15V, and the black test lead is the positive end relative to the red test lead. Digital watches usually have a 6V or 9V rechargeable battery. In the resistor file, the output current of the test pen of the pointer meter is much larger than that of the digital meter. Using the R×1Ω file can make the speaker emit a catchy “da” sound, and using the R×10kΩ file can even illuminate led diode (LED).
3. In the working voltage range, the internal resistance of the pointer meter is relatively small compared with the digital meter, and the measurement accuracy is relatively weak. Some places with high voltage and low current cannot even be measured accurately, because their 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 working voltage range of the digital meter is quite large, at least in the megohm level, which has little harm to the power circuit under test. However, the high output impedance makes it susceptible to the influence of magnetic induction voltage, and the statistical data measured in some places with strong interference signals may be false.
4. In other words, pointer meters can be used for accurate measurement of analog circuits with relatively high current and high operating voltage, such as TVs and speaker amplifiers. Digital meters can be used in the precise measurement of low-voltage and low-current digital circuits, such as BP machines, mobile phones, etc. It is not absolute, and pointer tables and digital tables can be used according to the situation.
safety operating procedures
1. Before using it, it is necessary to understand the various functions of the digital multimeter, and select the appropriate gear, measurement range and test lead socket according to the other half to be measured.
2. When the size of the measured data is unclear, first switch the power switch of the measurement range to the highest value, and then switch to the small measurement range by many steps, so that the pointer on the instrument panel is marked at about 1/2 of the full scale anywhere.
3. When measuring the resistor accurately, after selecting an appropriate multiple, collide the two test leads so that the pointer returns to zero. If the pointer is offset and returns to zero, adjust the "zero calibration" knob to reset the pointer to zero to ensure Precise measurements are precise. If zero calibration is not possible or a low pressure alarm is issued from the digital display, it should be checked in time.
4. When accurately measuring the resistance of a certain power circuit, be sure to disconnect the switching power supply of the power circuit under test, and do not induce electrification for accurate measurement.
5. When using a digital multimeter to measure, pay attention to personal safety and the safety of electrical instruments. During the test, do not touch the metal part of the test pen with your hands, and do not allow induction to change gears to ensure accurate measurement. , Prevent safety accidents such as electric shock accidents and damage to the instrument panel.
