It is measured with a definite target(part 1)

1. Use the multimeter correctly

Use multimeter correctly and be familiar with dial before use.Two zero adjusters, gently rotate to zero.Correctly select the terminal post and insert the red and black marker into the right hole.

The transfer switch should rotate the gear, and the gear should be selected correctly.Choose the proper range to make the measurement accurate.Calibration of the scale line, vertical surface reading accuracy.

After measuring the dial pen, the switch rotates in high voltage.The battery in the table often check, deterioration will leak hydrolysate.With good storage instrument environment, no vibration and no tidal magnetic field weak.

2. Correctly use the ohms of the multimeter

The correct use of ohm, should know that there should be eight.The battery voltage should be abundant, and the circuit under test has no voltage.Select the appropriate scale, needle point scale middle.

Each time the multiplier is changed, the resistance must be adjusted to zero.The measuring point contact is good, the measuring object pen end hand does not touch.Measuring circuit on and off, above 1000 - ohm range.

Judge and measure the diode element, the ratio is different resistance is different.Measure the winding of transformer. If touch hand, feel hemp electricity.

3. Matters needing attention when measuring voltage of multimeter

When measuring the voltage with a multimeter, there are eight precautions.Clear the size of the table resistance, someone must monitor.The circuit under test is in parallel, live can't change the range.

Make sure the positive and negative terminals of the circuit when measuring the DC voltage.Voltage of inductive reactance circuit can not be cut off during.Test kilovolt high voltage, must use special marker pen line.

Induction voltage to the ground, the range of different values of the big difference.

4. Method of measuring DC current with multimeter

Measure the current with a multimeter, switch to ma, determine the positive and negative of the circuit, the meter in series circuit.Choose a larger range to reduce the impact on the circuit.

5. Dc method to identify the head and tail ends of three-phase motor stator windings

Three - phase motor winding, head and tail DC method.Multimeter dial milliampere, DC power dry battery.One phase winding is connected to the meter and the other phase winding is connected to the battery.

When the power is on, the needle turns and the positive pole is the first.If there is no reverse transfer connection, the residual phase winding shall be judged as the same.

6. Remanence method to identify the head and tail ends of three-phase motor stator windings

The head and tail remanence method is used to judge the motor after operation.Three - phase winding outlet, after marking in parallel.Multimeter dial milliamperes, bonded parallel common points.

Slowly turn the motor shaft while watching the gauge needle.No obvious swing of pointer, three heads and three tails are connected.The pointer moves from side to side, two heads, one tail and one end.

One - phase winding switch head, and then use the same method to determine.Until the hand does not swing, end to end and end to end.

7. The head and tail ends of three-phase motor stator windings are identified by circulation method

Used motor, head and tail circulation method.Three - phase winding outlet, connected to each other in series into a triangle.The multimeter dials the milliamperes and connects the three-phase winding in series.

Rotate the motor shaft uniformly while watching the instrument needle.The pointer basically does not swing, the winding is connected head and tail.Pointer swing large, a phase winding head upside down.

Two connection points two lines, both head end and tail end.

8. Determine the three-phase motor speed with a multimeter

Three - phase motor speed, the use of multimeter measurement.Open the motor junction box and remove the junction block.Multimeter connected to the milliampere, spanning a phase winding.

Turn the rotor and watch the hands swing a few times.Two - pole motor swing once, synchronous speed 3000.Quadrupole motor swings twice, synchronous speed 1500.

Similarly, the speed is judged to be slightly lower than the synchronous speed.

9. Test the grounding resistance of the grounding protection wire installed in the family

The home is equipped with a ground wire to test the ground resistance value.Multimeter dial voltage range, kilowatt electric furnace to zero.The electric furnace terminal voltage is measured and the working current is calculated.

Switch the electric furnace to phase ground wire, and then measure the voltage at the end of the electric furnace.Two terminal voltage errors divided by the operating current value.Quotient ground resistance value, about 5% error.

10. Identify the phase line and neutral line of low-voltage AC power supply

Low-voltage three-phase four-wire system, power neutral phase line.Multimeter dial voltage range, 250 AC, one stroke connection point, another stroke and power cord

Pointer deflection radian is large, the table stroke is phase line.The hand is slightly deflected and the pen touches the neutral line.

11. The crystal diode polarity test and stand or fall

Determine diode polarity, multimeter dial thousand euro range.The resistance value is small thousand ohms and the diode forward resistance is measured.Black pen contact tube positive pole, red pen contact tube negative pole.

Measured resistance value tens of thousands of ohms, diode reverse resistance.The red brush takes over the positive and the black brush takes over the negative.

Judge the diode good or bad, multimeter dial thousand euro range.The larger the value, the better.The positive and negative resistance values are close, and the tested pipe has failed.

Positive and negative resistance values are zero, short circuit between the two poles of the pipe.Infinite resistance positive and negative. The pipe is open.

12. Test the quality of the high-voltage silicon reactor

Check the quality of the silicon stack, the multimeter dial voltage range.Silicon reactor multimeter series, bonded ac 220.Range DC 250, silicon reactor forward access.

More than 30 volts qualified, there is a fault when the watch hand does not move.Range AC 250, short circuit reading 220.The hands are still reading zero and the silicon stack is open.

13. Test and judge the quality of the capacitor

Microcapacitance capacitors are easy to measure and judge.Multimeter dial a thousand euro range, red and black watch pen connected to the poles.Watch hand left and right pendulum once, the bigger the better.

The hand does not swing at all, and the capacitance under test is open.Watch hand to zero does not return, the measured capacitance has been broken down.

14. Digital multimeter buzzer block detects the quality of electrolytic capacitor

Electrolytic capacitor quality, digital multimeter test.Switch to buzzer, red and black brush positive and negative.A short beep, sound stop overflow symbol display.

Buzzer sound time is long, capacitor capacity is larger.If the buzzer keeps ringing, the capacitor under test will short circuit.If the buzzer does not sound, the capacitor's internal circuit is broken.

15. Safety rules to follow when using a clamp ammeter

When using a clamp ammeter, keep safety rules in mind.High pressure circuit testing must be done by two persons.The potential of the conductor under test, not over clamp meter voltage level.

The operator must wear gloves and stand on the insulation cushion.Human head charged body, keep enough safe distance.Measurement of low voltage bus flow, insulation baffle with protection.

Poor insulation or bare wire, do not use pliers to measure.

16. The correct use of clamp ammeter

Use a clamp ammeter and choose the appropriate model and specification.Coarse measurement on the maximum range, reasonable selection of range gear.The middle wire of the pliers mouth is set, and the static and static iron core matches well.

After the clamp mouth is put into the wire, the live can't change the range.Clamp current voltmeter, current and voltage are measured respectively.Two lighting lines, not at the same time into the clamp mouth.

After each test of the clamp gauge, the range is set to the maximum.

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