Digital Multimeter: Steps & Resistance

Advantages of a multimeter

no external power source is required for its operation; therefore, no warm-up is necessary. Other advantages include its portability and versatility.

modern digital meters have considerably greater _________.

input impedances.

Most analog models feature two __________: one to select _________and one to select ________.

Most analog models feature two rotary switches: one to select function and one to select range.

Shift Button (Blue)

used to select these alternate functions

Identify : ))))))) button

Continuity signal button:

Audio signal or buzzer to indicate a short circuit. When the measured resistance falls below a preset level, the signal sounds to indicate the short.

Identify : MIN/MAX button

MIN/MAX mode stores minimum (MIN) and maximum (MAX) input values. New Minimum or Maximum values replace previous values.

Identify : HOLD button

freezes the present reading on the display, where it will remain until either the HOLD button is pushed again or the rotary switch is turned to a new function.

Identify : REL button

zeros the display and stores the present reading as a reference for subsequent readings.

Identify : Hz button

measure the frequency of an AC voltage or current signal in Hertz.

Safety Guidelines part 1

- Verify operation with known voltage

- Connect COM lead First. Disconnect Live lead first.

- turn off ckt power when measuring current

- Do not use meter w/ test leads with damaged insulation or exposed metal

- keep fingers behind finger guards

- do not use meter around explosive gas/vapors

Safety Guidelines part 2

- do not use meter with known safety defects

- deenergize ckt and discharge capacitors before measuring continuity, diodes, resistance, or capacitance

- set up proper function and range

- use proper terminals

- using test leads on powered ckts when leads connect to current terminals may cause meter to blow fuse

Identify : Yellow Button

sets the variable lcd backlight

While analog meters may have as many as _____ terminals, digital models tend to have ______.

While analog meters may have as many as eight terminals, digital models tend to have fewer.

A and COM terminals current range

50mA - 20A

mA/uA and COM terminals

below 50 mA

uA + COM

below 5000 uA

Before taking a resistance measurement with an analog multimeter, you must ______ the ohmmeter to ensure accurate readings

Zero

How to Zero Meter:

shorting the leads together and adjusting the OHMS ADJ control. The ZERO OHMS control is continuously variable and is used to adjust the meter circuit sensitivity to compensate for battery aging in the ohmmeter circuits.

It is necessary to zero the ohmmeter in a digital multimeter. True/False

False

In a continuity check for a digital multimeter; a reading of __________ ohms should be displayed.

0.1 OHM to 0.2 OHM

The apparent displacement of an object caused by a change in the position from which it is viewed.

Parallax

Voltage measurements are taken _______.

across a circuit (in parallel).

A multimeter will only cause measurement errors in ___________.

high impedance circuits.

The _______ the meter's input resistance, the less it will load the circuit.

Higher

Analog Multimeter Steps: Voltage

1. Select Function

2. Select Range

3. Connect leads to proper terminals

4. Connect leads to a difference of potential

5. Connect Black lead to GND and live lead to

test point if required.

Digital Multimeter Steps: Voltage

1. Attach leads

2. Turn off CKT

3. Select Function

4. Attach probes to Test points

5. Turn On Ckt

6. Turn off CKT

Digital Multimeter Steps: Resistance

1. Attach leads

2. Turn off ckt

3. Select Function

4. Attach probes

5. Remove probes

Analog Multimeter Steps: Resistance

1. Select resistance range

2. Attach leads

3. Zero Leads

4. Isolate component

5. Check contacts for dirt/grease

6. Touch only insulated part of leads

7. High Resist: Needle=Left

Low Resist: Needle=right

8. Adjust Range, midscale to slightly right

Zero resistance causes ________ deflection

full-scale

To measure current, you must ______ the circuit under test, then place the meter in ______with the circuit.

To measure current, you must open the circuit under test, then place the meter in series with the circuit.

Analog Multimeter Steps: Current

1. De-energize the CKT and discharge all capacitors.

2. Set the function switch to +DC

3. Attach Leads

4. Select Ampere Range

5. Attach probes

6. Energize the CKT and take the reading using the DC scale.

Diodes must be ___________ before testing.

electrically isolated

The normal voltage drop across a PN junction is about _______ for germanium and ______ for silicon diodes

The normal voltage drop across a PN junction is about .3V for germanium and .7V for silicon diodes.

Before testing a diode, always _______ the circuit and ________ all capacitors.

Before testing a diode, always de-energize the circuit and discharge all capacitors.

Digital Multimeter Steps: Diodes

1. Attach Leads

2. De-energize CKT

3. Select Function

4. Attach probes

5. Reverse probes

6. Remove probes

Digital Multimeter Steps: Current

1. Attach Leads

2. De-energize CKT

3. Select Function

4, Attach probes

5. Energize CKT

6. De-energize CKT

7. Remove leads

Troubleshooting checklist

- connections good between the component to be tested and surrounding components?

- contacts clean?

- blown fuses?

- any obviously burned out components?

System which technical manuals define a set procedure to follow based on particular symptoms.

Procedural

This method involves starting the troubleshooting in the middle of a circuit to check for problems

half-split method

Why should CKT cards be troubleshooted before replacement?

swapping cards is very expensive