How to use a multimeter and what to pay attention to

A multimeter is also called a universal meter, which can be used to measure AC and DC voltage, AC and DC current, resistance, and many other measurements. Let's take the MF500B multimeter as an example to understand how to use the multimeter:

1. Place the multimeter horizontally. Adjust the mechanical zero adjuster so that the pointer of the multimeter points to the zero position of the scale (left).
2. Insert the red test rod into the "+" jack and the black test rod into the "*" jack, and select the corresponding measurement gear.
① When measuring DC voltage, put the gear switch knob on the right in the "V" position; select the gear of the left switch knob according to the approximate value of the measured voltage (500V, 250V, 50V, +V, 2.5V). The red test rod is connected to the + end of the measured voltage, and the black test rod is connected to the - end of the measured voltage. If the needle rotates, swap the red and black test rods at the measured voltage end. When the value of the measured voltage is close to 2500V, the red test rod should be inserted into the "2500V" jack.
②When measuring AC voltage, place the right gear switch knob in the "V" position; select the gear of the left switch knob (500V, 250V, 50V, +V) according to the approximate value of the voltage to be measured. When the value of the measured voltage is close to 2500V, the red test rod should be inserted into the "2500V" jack.
Note: When measuring voltage: both the left and right gear switch knobs should be placed in the gear with the "V" symbol.
③When measuring DC current, place the left gear switch knob in the "A" position; select the gear of the right switch knob (500mA, +0mA, +10mA, 1mA, 50μA) according to the approximate value of the current to be measured. The red test rod is connected to the + end of the current to be measured, and the black test rod is connected to the - end of the current to be measured.
④When measuring AC current, put the left gear switch knob in the "A" position; select the gear of the right switch knob (500mA, +0mA, +10mA, 1mA, 50A) according to the approximate value of the current being measured.
That is: when measuring current: both the left and right gear switch knobs should be placed in the gear with the "A" symbol.
When the value of the measured current is close to 5A, the red test rod should be inserted into the "5A" jack.
⑤When measuring resistance, put the left gear switch knob in the "Ω" position; select the gear of the right switch knob (+10KΩ, 1KΩ, +0Ω, +10Ω, 1Ω) according to the approximate value of the resistance being measured. Short-circuit the red and black test rods, adjust the adjuster marked with "Ω" so that the pointer of the multimeter points to the zero position of the Ω scale (on the right). If the pointer cannot be adjusted to zero, it means that the battery in the meter is missing and a new battery should be replaced.
That is, when measuring resistance, both the left and right position switch knobs should be placed in the position with the "Ω" symbol.
Measurement readings and values:
There are five scales on the MF500B multimeter dial, including Ω, -, +V, A, and -dB.
① When measuring resistance, read the scale of the "Ω" scale (the first one above):
the resistance measurement value = reading × the position of the right position switch knob.
(The gear numbers of the right gear switch knob are +10KΩ, +10KΩ, +0Ω, +10Ω, and +1Ω)
For example: the measured reading is 20: when the gear is at +10KΩ, the measured value is 20×+10KΩ=200KΩ;
the measured reading is 40: when the gear is at +10Ω, the measured value is 40×+10Ω=400Ω;
② When measuring DC and AC voltages as well as DC and AC currents, read the scale of the “-” scale (the second one above):
3; The measured value of voltage (current) = reading × the number of gears of the left (or right) gear knob address ÷ the full-scale reading of the scale.
The gear numbers of the left gear switch knob are 2.5V, +10V, 50V, 250V, and 500V)
(The gear numbers of the right gear switch knob are 50A, 1mA, +10mA, +100mA, and 500mA)
(The full-scale readings of the scale are 50 and 250)
For example: when the gear of the switch knob is at 250V, the measured reading is 215, and the full-scale reading of the scale is 250: The
voltage measurement value = 215×250V÷250=215V
The gear of the switch knob is at +10mA, the measured reading is 40, and the full-scale reading of the scale is 50:
The current measurement value = 40×+10mA÷50 =80mA
4. Note
① When the approximate value of the measured electricity cannot be estimated, the gear of the switch knob should be set to the maximum first, and then the gear of the switch knob should be selected according to the
approximate .
②When measuring current, the multimeter should be connected in series to the circuit being measured. Pay attention to the positive and negative polarities when measuring DC current. If the probe is connected in reverse,
the needle will be reversed and easily bent.
③Do not measure resistance with power on.
④When using the multimeter, do not touch the metal part of the test rod with your hands. This can ensure the accuracy of the measurement on the one hand and personal safety on the other. When measuring high voltage, you must take necessary safety measures.
⑤When measuring a certain amount of electricity, you cannot change gears while measuring, especially when measuring high voltage or high current. Otherwise, the multimeter will be damaged. If you need to change gears, you should measure continuously first, and then continue measuring after changing gears.
⑥When the multimeter is finished, the conversion switch should be set to the maximum gear of the AC voltage. If it is not used for a long time, the battery inside the multimeter should also be taken out to prevent the battery from corroding the equipment inside the meter.