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Difficulty: MediumMultimeter: Voltage and Current Measurement

A technician is troubleshooting a low-voltage DC power supply circuit and needs to measure the operational current supplied to a control module. To obtain an accurate measurement while protecting the digital multimeter (DMM) and the circuit, how should the meter be configured and connected?

  1. A
    Set the dial to DC current (DCA), insert the red test lead into the current (mA/A) input jack, and place the test leads in parallel across the positive and negative supply terminals.
  2. Set the dial to DC current (DCA), insert the red test lead into the current (mA/A) input jack, and connect the meter in series by breaking the circuit line.Answer
  3. C
    Set the dial to DC voltage (DCV), insert the red test lead into the voltage (V/Ω\Omega) input jack, and place the meter in series by opening the circuit line.
  4. D
    Set the dial to AC current (ACA), insert the red test lead into the voltage (V/Ω\Omega) input jack, and place the test leads in parallel across the load.

Answer

Set the dial to DC current (DCA), insert the red test lead into the current (mA/A) input jack, and connect the meter in series by breaking the circuit line.
Measuring electrical current requires the ammeter to be inserted in series with the circuit path so that the electron flow passes directly through the meter's low-resistance internal shunt. The technician must set the rotary selector to direct-current amperage (DCA) and plug the positive (red) test lead into the designated fused current (mA or A) terminal, keeping the black lead in the common (COM) port.

Step-by-Step Solution

1
Select the proper measurement function and range on the rotary dial.
The meter is configured for DC current (DCA/mA/A) to accurately sample direct-current flow.
Multimeters require matching the function to the electrical parameter and waveform type being evaluated.
2
Insert the meter test leads into the correct input terminals (black lead in COM, red lead in the fused mA or A jack).
The internal low-resistance current shunt is engaged in the measurement circuit.
Voltage and current measurements use separate internal circuitry; current must route through a dedicated fused input jack.
3
De-energize the circuit, open the conduction path, and connect the meter leads in series with the load before re-energizing.
The full circuit current flows through the meter without bypassing the load.
Ammeters must be placed in series because current is a through-variable that flows through components.

Key Concept

Digital Multimeter Current Measurement Configuration and Series Insertion
Estimated Time:1m 0s
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Topics

Multimeter: Voltage and Current Measurement

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