An electrically savvy handyman frequently carries a digital multimeter in his tool box or service vehicle. A properly used multimeter measures both voltage and current for alternating current, or AC. The multimeter also measures voltage and current for direct current, or DC. Electronic hobbyists can also test diodes, resistors and transistors with the Cen-Tech 92020 digital multimeter. Safety-conscious workmen and hobbyists receive prior instruction in the multimeter’s operation, as the device measures potentially deadly electrical voltages.
Measuring AC Voltage
Place the red lead’s plug end into the jack marked “V-ohm-mA.” Place the black lead’s plug end into the jack marked “COM.”
Set the multimeter to read AC voltage. Turn the range selector knob to the position marked “750 ACV.”
Turn the meter on. Slide the power switch to the “On” position.
Touch each probe to the item for which voltage is being measured. Use the probe ends of the leads. Do not allow your fingers to touch the probes, as lethal voltage may be present.
Read the digital display’s indicated voltage. Adjust the range selector knob to a lower range if the voltage is less than 200 volts.
Turn the meter off. Slide the power switch to the “Off” position.
Measuring DC Voltage
Place the red lead’s plug end into the jack marked “V-ohm-mA.” Place the black lead’s plug end into the jack marked “COM.”
Set the multimeter to read DC voltage. Turn the range selector knob to the position marked “1,000 VDC.”
Turn the meter on. Slide the power switch to the “On” position.
Touch each probe to the item for which voltage is being measured. Use the probe ends of the leads. Do not allow your fingers to touch the probes, as lethal voltage may be present.
Read the digital display’s indicated voltage. Adjust the range selector knob to a lower range if the voltage is less than 200 volts.
Turn the meter off. Slide the power switch to the “Off” position.
Measuring DC Current
Place the red lead’s plug end into the jack marked “10A.” Place the black lead’s plug end into the jack marked “COM.”
Set the multimeter to read DC current. Turn the range selector knob to the “10A” position.
Turn the meter on. Slide the power switch to the “On” position.
Touch each probe to the item for which current is being measured. Use the probe ends of the leads.
Read the digital display’s indicated current. Adjust the range selector knob to the “200 mA setting.” Move the red plug to the “VmA” jack if the reading is 200 mAmps or less.
Turn the meter off. Slide the power switch to the “Off” position.
Measuring Resistance
Turn off the power to the device for which resistance is being measured. This ensures the multimeter will not be damaged.
Place the red lead’s plug end into the jack marked “V-ohm-mA.” Place the black lead’s plug end into the jack marked “COM.”
Set the multimeter to read resistance. Turn the range selector knob to the “200 ohm" position.
Turn the meter on. Slide the power switch to the “On” position.
Touch the red and black probes together. The display should indicate a resistance of 0 ohms.
Touch each probe to the item for which resistance is being measured. Use the probe ends of the leads.
Read the digital display’s indicated resistance. Adjust the range selector knob to the next higher setting if the meter reads “1.”
Turn the meter off. Slide the power switch to the “Off” position.
Measuring Transistor hFE or Gain
Set the multimeter to read transistor hFE. Turn the range selector knob to the “hFE” position.
Turn the meter on. Slide the power switch to the “On” position.
Insert the transistor pins into the appropriate transistor jack; either “NPN” or “PNP.” Place the transistor’s emitter pin in the “E” jack. Place the collector in the “C” jack. Place the base in the “B” jack. Obtain the type of transistor and pin out from online reference material.
Read the transistor’s hFE indicated on the digital display.
Turn the meter off. Slide the power switch to the “Off” position.
Measuring Diode Voltage Drop.
Place the red lead’s plug end into the jack marked “V-ohm-mA.” Place the black lead’s plug end into the jack marked “COM.”
Set the multimeter to read diode voltage drop. Turn the range selector knob to the diode position.
Turn the meter on. Slide the power switch to the “On” position.
Touch the black probe to the diode’s cathode. Touch the red lead to the diode’s anode. Use the probe ends of the leads. The cathode has a dot or ring marking on the diode.
Read the diode voltage drop indicated on the digital display.
Turn the meter off. Slide the power switch to the “Off” position.
References
Writer Bio
Robert Osborne has written professionally since 2010. He writes for eHow, specializing in aircraft and boat maintenance, home renovation and electrical engineering. Osborne earned his Bachelor of Science in electrical engineering from George Washington University.
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