Extech Instruments CT40 User's Guide download pdf (Page 5)

CT40- EU-EN V1.7 1/13

Digital Multimeter Functions

AC/DC Voltage Measurements

1. Insert the black test lead into the negative COM terminal and the red test lead into the positive

V terminal.

2. Set the rotary function switch to VAC or VDC position.

3. Connect the test leads in parallel to the circuit under test.

4. Read the voltage measurement on the LCD display.

CAUTION: Do not measure AC/ DC voltages if a motor on the circuit is being switched ON or

OFF. Large voltage surges may occur that can damage the meter.

AC/DC Current Measurements

1. Set the function switch to the µA/mA position.

2. Insert the black test lead into the negative COM terminal and the red test lead into the positive

µA/mA terminal.

3. For current measurements up to 2000µA DC/AC, set the function switch to the mA position

4. Press the MODE button to indicate “DC” / “AC” on the display.

5. Connect the meter in series with the circuit under test, the black test probe tip to the negative

side of the circuit and the red test probe tip to the positive side of the circuit.

6. Apply power to the circuit.

7. Read the current in the display

Resistance Measurements

1. Set the function switch to the Ω position.

2. Insert the black test lead into the negative COM terminal and the red test lead into the positive

Ω terminal.

3. Touch the test probe tips across the circuit or part under test. It is best to disconnect one side

of the part under test so the rest of the circuit will not interfere with the resistance reading.

4. Read the resistance in the display

WARNING: To avoid electric shock, disconnect power to the unit under test and discharge all

capacitors before taking any resistance measurements.

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Extech Instruments CT40 User's Guide Page 5