How to use a multimeter by princemoses

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									Digital Multimeter

http://www.physics.smu.edu/~scalise/apparatus/multimeter/

Digital Multimeter

1. Function/Range Switch: selects the function (voltmeter, ammeter, or ohmmeter) and the range for the measurement. 2. COM Input Terminal:Common ground, used in ALL measurements. 3. V Input Terminal: for voltage or resistance measurements.

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Digital Multimeter

http://www.physics.smu.edu/~scalise/apparatus/multimeter/

4. 200 mA Input Terminal: for small current measurements. 5. 10 A Input Terminal: for large current measurements. 6. Low Battery LCD: appears when the battery needs replacement.

Precautions for Voltage Measurements
Plug the black test lead into the COM jack. Plug the red test lead into the V jack. Set the function/range switch to either DC volts in the upper left, or AC volts in the upper right. If you do not know the approximate voltage about to be measured, use the largest voltage range available. Connect the free ends of the red and black test leads ACROSS the device to the measured. Voltage is always measured with the meter in PARALLEL with the device. If the LCD displays either "1." or "-1." with all other digits blank, the voltage is beyond the selected range. Use the switch to select a larger range. Once you know the approximate voltage across the device, then use the switch to select the lowest voltage range that will still accomodate the voltage across the device. For example: Range 1000 VDC 200 VDC 20 VDC 2 VDC Actual value 18.75 V 18.75 V 18.75 V 18.75 V Display 19 18.8 18.75 1. Comments Reduce range Reduce range Correct range Overload - increase range

Precautions for Current Measurements
Turn the power off to the device and discharge any capacitors! Plug the black test lead into the COM jack.
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Digital Multimeter

http://www.physics.smu.edu/~scalise/apparatus/multimeter/

Plug the red test lead into either the 200 mA jack for small current measurements, or the 10 A jack for large current measurements. If you do not know the approximate current about to be measured, use the 10 A jack. Set the function/range switch to either DC amperes in the lower right, or AC amperes in the middle right. Break open the circuit at the point where you want to measure the current by removing one of the wires. Connect the free end of the red test lead to one place at which the wire was attached. Connect the free end of the black test lead to the other place at which the wire was attached. Current is always measured with the meter in SERIES with the device. If you do not understand the difference between SERIES and PARALLEL, ask your TA. Using the current meter incorrectly will blow the fuse or damage the meter. (It will also cost you points on your lab writeup.) Reapply the power to the device. If the LCD displays either "1." or "-1." with all other digits blank, the current is beyond the selected range. Use the switch to select a larger range. Once you know the approximate current through the device, then use the switch to select the lowest current range that will still accomodate the current through the device. Turn the power off to the device before removing the meter from the circuit.

Precautions for Resistance Measurements
Turn the power off to the device and discharge any capacitors! Plug the black test lead into the COM jack. Plug the red test lead into the V jack. Set the function/range switch to ohms ( ) in the lower left. If you do not know the approximate resistance about to be measured, use the largest range available. Connect the free ends of the red and black test leads ACROSS the device to the measured. Resistance is always measured with the meter in PARALLEL with the device. If the LCD displays either "1." or "-1." with all other digits blank, the resistance is beyond the selected range. Use the switch to select a larger range. Once you know the approximate resistance of the device, then use the switch to select the lowest range that will still accomodate the resistance of the device.

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1/27/2010 7:54 PM

Digital Multimeter

http://www.physics.smu.edu/~scalise/apparatus/multimeter/

Picture of a meter in parallel with device
Measure voltage and resistance this way:

Picture of a meter in series with device
Measure current this way:

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