As the multimeter to measure voltage, resistance and current in the electrical circuit
See how in practice multimeter measured the electrical voltage as measured by multimeter current, as measured by multimeter resistance.
Multimeter measures the electrical voltage
Measure multimeter electrical voltage, for example, the automotive battery. Car battery is a source of constant current and voltage at its terminals is approximately 12 V. Therefore DCV measurements use a multimeter sector.
Our actions when measuring the voltage will be such.
- First, connect the cables to the multimeter: black jack kabel- COM, red cable - jack VΩmA.
- When measuring voltage multimeter is used as a voltmeter and joins the parallel measurement object. Enables multimeter, set the range switch to 20V, connect the measurement cables to the battery, the black wire (COM) to the negative pole of the red cable (V) to the positive pole. If anything off or disconnect in the electrical circuit is required. Measurement scheme is shown below.
- The display shows the value of voltage.
Note. If the display of digital multimeter just see figure 1 with no other digits - this indicates too small selection of the measuring range.
Multimeter measures DC
We must remember that simple multimeters, such as DT 830V, designed to measure only direct current, alternating current measuring them is impossible.
The sequence of your actions in the multimeter measurement of electric current is.
- First, connect the cables to the multimeter: black cable - jack COM, red cable - jack VΩmA (when measuring currents up to 200 mA) and jack 10A (when measuring currents from 200 mA to 10 A).
- When measuring currents of 200 mA jog dial to set the position 10A, while the measurement of currents up to 200 mA - the sector DCA. When there is doubt, the measurement should start with greatest limit of measured.
- When measuring current multimeter used as ammeter. Connect it to the object of measurement series. Enables multimeter, set the switch to the desired range. Break the electric circuit and the ends of the cables touch the circle, the black wire (COM) connected to the negative pole of the power supply, red cable (V) - to the positive pole.
- If you connect a multimeter to measure current in parallel mode (as a voltmeter), the best fuse fails, and at worst - multimeter. Measurement scheme is shown below.
- The display shows the current value multimeter.
Importantly! In case you try to measure the limits of 200 mA more current measure, it will lead to failure of fuse inside multimeter (change required for a similar fast fuse 200 mA nominal value of 250 V). Log 10A fuse is not protected! Measurement of high currents try to execute the shortest possible time, do not leave the unit included in the measuring chain for a long time when measuring high currents - multimeter can fail. Some manufacturers recommend measurement of current over 5A do not longer than 15 seconds.
How to measure the electrical resistance multimeter (ohmmeter mode)
Multimeter used to measure the resistance of the circuit, resistors and to verify the integrity connecting wires. Voltmeter multimeter can measure only the resistance and reactance capacitances and inductances AC ohmmeter measure can not. Unlike current measurement mode and voltage measurements Ohmmeter can start as from the lowest range, and the most.
Measurements of electrical resistance multimeter connected in parallel to object, the resistance which must be determined. In this case, given electric circuit must be completely de-energized and it should not leak electricity. Otherwise multimeter fails.
For example, we multimeter to measure the resistance of the indicator in a simple electrical circuit. The sequence of our actions is.
- Eliminates power circuit.
- Disconnect the indicator from the circuit.
- Connect the cables: black cable - jack COM, red cable - jack VΩmA.
- The rotary switch is set to position Ω
- Connect the multimeter probes and the display shows the value of resistance.
Measurement scheme is shown below.
Importantly! When using a multimeter to measure electrical resistance mode remember:
- electric range or object that you want to measure resistance Ohmmeter should be completely without electricity;
- the closer the measured value to the selected measuring range, the more accurate the measurement result (with the display of multimeter symbol "1" (overload) should switch to the range of measurement;
- when measuring small resistances must be considered resistance probes;
- when measuring large resistance values (MW) installation possible long-term rate - a gradual slow growth rate of the nominal value.
Remember! Serviceability checked locking ohmmeter probes to each other. In that case, your multimeter should be close to zero. If the closure probes multimeter does not indicate the exact zero (it can not happen through the use of native probes, discharge batteries, etc.) necessary to make an amendment to the measured value by the amount of error.