Pointer multimeter application notes

　　How to use a pointer multimeter

　　(1) Be familiar with the meaning of each symbol on the dial and the main functions of each knob and selector switch.

　　(2) Perform mechanical zero adjustment.

　　(3) According to the type and size of the object being measured, select the position and range of the conversion switch and find the corresponding scale line.

　　(4) Select the location of the test lead jack.

　　(5) Measuring voltage: When measuring voltage (or current), you must select the right range. If you use a small range to measure a large voltage, there is a risk of burning the meter; if you use a large range to measure a small voltage, the pointer deflection is too small and the reading cannot be read. The range should be selected so that the pointer deflects to about 2/3 of the full scale. If the magnitude of the voltage to be measured is not known in advance, you should first select the highest range and then gradually reduce it to the appropriate range.

　　a Measurement of AC voltage: Set one switch of the multimeter to the AC/DC voltage range, and the other switch to the appropriate AC voltage range. Connect the two test leads of the multimeter in parallel with the circuit or load to be measured.

　　b. Measurement of DC voltage: Set one of the multimeter's switches to the AC/DC voltage position, and the other switch to the appropriate DC voltage range, and connect the "+" probe (red probe) to the high potential, and the "-" probe (black probe) to the low potential, that is, let the current flow in from the "+" probe and out from the "-" probe. If the probes are connected in reverse, the pointer will deflect in the opposite direction, which can easily bend the pointer.

　　(6) Measuring current: When measuring DC current, set one of the multimeter's switches to the DC current position and the other switch to the appropriate range from 50uA to 500mA. The current range selection and reading method are the same as those for voltage. When measuring, the circuit must be disconnected first, and then the multimeter is connected in series to the circuit being measured in the direction of the current from "+" to "-", that is, the current flows in from the red test lead and out from the black test lead. If the multimeter is mistakenly connected in parallel with the load, the internal resistance of the meter head is very small, which will cause a short circuit and burn the instrument. The reading method is as follows:

　　Actual value = indicated value × range / full scale

　　(7) Measuring resistance: When measuring resistance with a multimeter, the following method should be followed:

　　a Mechanical zero adjustment: Before use, the pointer positioning screw should be adjusted to make the current reading zero to avoid unnecessary errors.

　　b. Choose the appropriate multiplier. The scale lines of the ohm range of the multimeter are uneven, so the multiplier should be selected so that the pointer stays in the part with fewer scale lines. The closer the pointer is to the middle of the scale, the more accurate the reading. In general, the pointer should be between 1/3 and 2/3 of the scale.

　　c. Ohm zero adjustment. Before measuring resistance, short-circuit the two test leads and adjust the "Ohm (electrical) zero adjustment knob" at the same time so that the pointer just points to the zero position on the right side of the ohm scale line. If the pointer cannot be adjusted to zero, it means that the battery voltage is insufficient or there is a problem inside the meter. And every time you change the magnification gear, you must perform ohm zero adjustment again to ensure accurate measurement.

　　d Reading: The reading on the meter multiplied by the multiplier is the resistance value of the resistor being measured.

　　Pointer multimeter precautions

　　aWhen measuring current or voltage, do not change the range while the power is on.

　　b When selecting a range, select the larger one first and then the smaller one, and try to make the measured value close to the range.

　　c. When measuring resistance, do not measure with power on. This is because the multimeter is powered by an internal battery, and if it is measured with power on, it is equivalent to connecting an additional power source, which may damage the meter head.

　　d After use, the conversion switch should be placed in the maximum AC voltage position or neutral position.

　　eNote that when the ohmmeter changes its range, ohm zero adjustment is required, and mechanical zero adjustment is not required.