A more comprehensive method of using a multimeter

To minimize incorrect readings of unknown voltages that contain AC or both AC and DC voltage components, first select the AC voltage function on the FLUKE 15B Multimeter, specifically noting the AC range required to produce the correct measurement. Then, manually select the DC function with a DC range equal to or higher than the AC range noted previously. Use this procedure to minimize the effects of AC transients when making precise DC measurements.
NK Select AC or DC by turning the rotary switch to = , = , or = .
OK Insert the red test lead into the = = terminal and the black test lead into
the COM terminal.
PK Touch the probes to the desired circuit test points and measure the voltage.
QK Read the measured voltage on the display.
FLUKE 15B Multimeter NOTE
Manual range selection on the FLUKE 15B Multimeter is the only way to access the 400 range.

PK To perform a duty cycle measurement, press the = = button again.
QK Read the duty cycle percentage on the display.
FLUKE 17B Multimeter Maintenance
Except for battery and fuse replacement, do not attempt to repair or service your FLUKE 17B Multimeter unless you are a qualified professional technician with adequate calibration, performance testing, and repair equipment. The recommended calibration period is =NO= months.

2. How to use Fluke 18B digital multimeter correctly

Fluke 18B Digital Multimeter Manual and Automatic Range Selection

Fluke multimeters have both manual and auto range options. In auto range mode, the Fluke multimeter selects the best range for the detected input. This lets you switch test points without resetting the range. You can change the auto range by manually selecting the range. In measurement functions that have more than one range, the meter defaults to auto range mode. When the Fluke multimeter is in auto range mode, Auto Range is displayed.
To enter and exit manual range mode:
2. Press R to increase the range. When the highest range is reached, the meter returns to the lowest range.
3. To exit manual range mode, press and hold R for two seconds.
Fluke 18B digital multimeter data hold
To hold the current reading, press H. Press H again to resume normal operation.
Fluke 18B digital multimeter AC or DC voltage measurement

To minimize false readings from unknown voltages containing AC or a mixture of AC and DC, first select the AC voltage function on the meter, taking note of the AC range that produces the correct measurement. Then, select the DC voltage function so that the DC range is equal to or higher than the previous AC range. This process minimizes the effects of AC transients and ensures accurate DC measurements.
1. Adjust the knob to v, V, or M to select AC or DC.
2. Connect the red test lead to the L terminal and the black test lead to the COM terminal.
3. Touch the probes to the desired circuit test points and measure the voltage.
4. Read the measured voltage on the display.
Fluke 18B Digital Multimeter Note
The 400 mV AC range can only be adjusted by manual ranging. AC or DC Current Measurement 

Fluke 18B digital multimeter AC or DC current measurement

1. Adjust the knob to A, /, or N.
2. Press the "Yellow" button to switch between AC or DC current measurement.
3. Connect the red test lead to the A, or mA i terminal, depending on the current to be measured, and the black test lead to the COM terminal.
4. Disconnect the circuit path to be tested. Then connect the test leads to the break and apply power.
5. Read the measured current on the display. Resistance Measurement
Fluke 18B Digital Multimeter Note
To avoid damage to the multimeter or the equipment under test, turn off the power to the circuit and discharge all high-voltage capacitors before measuring resistance.
1. Turn the rotary switch to F. Make sure the power to the circuit to be tested is turned off.
2. Connect the red test lead to the L terminal and the black test lead to the COM terminal, as shown in Figure 3.
3. Touch the probes to the desired circuit test points and measure the resistance.
4. Read the measured resistance on the display.

Fluke 18B Digital Multimeter Continuity Test

Select the resistance mode and press the "Yellow" button twice to activate the continuity beeper. If the resistance is below 50 Ω, the beeper will sound continuously, indicating a short circuit. If the meter reads o, the circuit is open.

Fluke 18B Digital Multimeter Diode Test

Fluke 18B Digital Multimeter Note
To avoid damage to the multimeter or the device under test, disconnect the circuit power and discharge all high-voltage capacitors before testing the diode.
1. Turn the rotary switch to F.
2. Press the "Yellow" function button once to start the diode test.
3. Connect the red test lead to the L terminal and the black test lead to the COM terminal.
4. Connect the red probe to the anode of the diode to be tested and the black probe to the cathode.
5. Read the forward bias voltage on the display.
6. If the polarity of the test lead is opposite to the polarity of the diode, the display reads o. This can be used to distinguish the anode and cathode of the diode.
Fluke 18B Digital Multimeter Capacitance Measurement
Fluke 18B Digital Multimeter Note
To avoid damage to the meter, disconnect the circuit power and discharge all high-voltage capacitors before measuring capacitance.
1. Turn the rotary switch to c.
2. Connect the red test lead to the L terminal and the black test lead to the COM terminal.
3. Touch the probes to the capacitor pins. After the reading stabilizes (15 seconds), read the capacitance value shown on the display.
Fluke 18B Digital Multimeter LED Test
Fluke 18B Digital Multimeter Note
During the test, to avoid damage to the meter or the equipment under test, disconnect all test leads connected to dangerous voltages before switching to the LED TEST function. The meter can measure light-emitting diodes (LEDs) through the LED TEST jack on the meter or through the test leads.
Fluke 18B Digital Multimeter Note
Do not use the LED TEST mode to perform LED aging tests. To measure LEDs through the LED test jack:
1. Adjust the knob to LED TEST.
2. Place the LED pin in the LED test jack on the front of the meter, as
shown in Figure 4.
If the LED under test is functioning properly, the LED under test plugged into the test jack will light up, and the indicator light adjacent to the positive "+" pin of the LED under test will also light up. If the LED under test is damaged, the LED under test will not light up.

Fluke 18B digital multimeter uses the test lead to test the LED:

1. Adjust the knob to LED TEST.
2. Connect the red test lead to the L terminal and the black test lead to the COM terminal, as shown in Figure 5.
3. Touch the LED pin with the test lead tip.
If the LED under test is functioning properly, the LED under test should light up, and the meter display will show the forward bias voltage (Vf) at this time. If the displayed value is positive, it means that the red test lead connected to the L terminal is connected to the positive terminal (+) of the LED under test. If the displayed value is negative, it means that the black test lead at the COM terminal is connected to the positive terminal (+) of the LED under test. If the LED under test is damaged, the LED will not light up, and the meter display will show close to 00.00.
The multimeter can test one LED with the test lead while lighting another LED using the LED test jack. However, the meter only displays the forward bias voltage (VF) of the LED tested with the test lead.