Mechanical Pointer Multimeter Measurement of Resistance
Choose the right magnification gear: when measuring resistance, the choice of magnification gear to make the pointer stay in the thinner part of the scale is appropriate. The closer the pointer is to the center of the scale, the more accurate the reading; the further to the left, the more crowded the scale line, the less accurate the reading. The multiplier block should be smaller than the measured value.
Zeroing: Before measuring the resistance, the test pens should be touched together, while rotating the "zero knob", so that the pointer just points to the zero position of the ohm scale, this step is called the ohm gear "zero". Every time you change the multiplier block to measure the resistance before, have to repeat this step, which is to ensure the accuracy of the measurement of essential steps. If the pointer can not be adjusted in place, indicating that the battery voltage is insufficient or the instrument circuit has a problem.
Can not be charged resistance measurement: measurement of resistance, the multimeter powered by the battery, the measured resistance must not be able to be charged, because charged measurement is equivalent to access to an additional power supply, not only do not get the correct measurement data, but also may be damaged meter head. The actual value of the measured resistance which comes: the actual value of the measured = multiplier × pointer reading. Such as in the 1000 multiplier block on the measurement of resistance readings for 25, then the measured resistance value of 25 × 1000 = 25000 ohms.
The method of measuring current with multimeter
First determine the object to be measured is alternating current or direct current, and then select the gear, the first with the highest current gear measurement, the meter pen connected in series in the circuit (DC meter pen to determine the positive and negative poles, connected to the wrong pen will be anti-strike the pointer, and then measured, according to the measured value and then select the corresponding gear and then carry out accurate measurements. (Pointer multimeter maximum range 5A)
Selectivity: The DC current range of multimeter is labeled as mA with three ranges of lmA, 10mA and 100mA. Selection of range, should be based on the current in the circuit. 1, selective range: the multimeter DC current file labeled mA has lmA, 10mA, 100mA three ranges. Select the range, should be based on the size of the current in the circuit, such as do not know the size of the current, should be selected with the maximum range.
Measurement of current, the table will be adjusted to the current file, if you do not know how much current from the high-grade gradually adjusted to a low gear, disconnect the circuit a foot, the meter pen positive and pay the pole in series connected to the circuit can be. To distinguish between AC and DC ah. Measurement of electric car current, the general multimeter does not have such a large range, to use a special ammeter, otherwise it will burn the multimeter.
Measure current with a multimeter, different from the measurement of voltage as simple, be sure to connect the multimeter in series to the circuit. As for how to use the multimeter do not need to talk about it.
Note that the impedance of the multimeter current measurement file is very small, before measuring the current size of the circuit should be measured beforehand to have an estimate, so as to select the appropriate range, so as to avoid the current over the range of the meter burned!
