Excepts from An Introduction to Using the Agilent 54622D Digital Oscilloscope E3631A DC Power Supply 34401A Digital Multimeter and 33220A Arbitrary Waveform Generator by Walter Banzhaf University of Hartford Ward College of Technology USA Part Four The Agilent 34401A Digital Multimeter 1 Measuring DC and AC Voltage 2 Measuring Resistance 3 Measuring Current Part Four The Agilent 34401A Digital Multimeter The DMM digital multimeter is a very important laboratory instrument This section will show you how to make three of the basic measurements voltage resistance and current The 34401A has many capabilities beyond measuring V R and I consult the Agilent User s Guide for information on measuring frequency period continuity diodes and using the many features and functions of this DMM When you turn the DMM on it will be in the Power On and Reset State Function DC volts Input resistance 10M may be changed to 10G for 100 mV 1 V 10 V DC ranges Range Resolution Autorange 5 digits Measuring DC and AC Voltage Key points You must insert the voltmeter leads across the two points in a circuit for which you want to measure the voltage Use the red and black input jacks as shown below You can use the rear panel red and black input jacks also be sure to select front or rear If you use front and rear you can easily and quickly select one of two voltages The DMM will Autorange unless you override it by selecting a range You can choose the number of digits displayed using the DIGITS buttons Be sure to select DC V or AC V as needed AC voltage displayed is the true RMS value of the waveform AC voltage is accurate to less than 1 up to 100 kHz Input impedance for AC V is 1M in parallel with 100 pF not including test leads Input resistance for DC V is 10M unless changed to 10G for 100 mV 1 V 10 V DC ranges Use these two red and black terminals Measuring Resistance Key points NEVER measure resistance in a live circuit Turn off all power to the circuit If an ohmmeter is used in a live circuit at best you will get incorrect readings at worst you can seriously damage the DMM You must insert the ohmmeter leads across the two points in a circuit for which you want to measure the resistance Use the red and black input jacks as shown below Use the red and black input jacks on the right as shown below You can use the rear panel red and black input jacks also be sure to select front or rear If you use front and rear you can easily and quickly select one of two voltages The DMM will Autorange unless you override it by selecting a range You can choose the number of digits displayed using the DIGITS buttons Be sure to select 2W ohms two wire 4W ohms four wire is a more complex measurement that gives greater accuracy by eliminating the contact resistance of the leads to the device under test Make sure your hands don t contact both test leads if they do then you re measuring the device under test in parallel with you See User s Guide page 216 for the test current for each resistance range Measuring Current Key points You must insert the ammeter leads in series to measure current in a circuit Use the red and black input jacks on the right as shown below You can use the rear panel red and black input jacks also be sure to select front or rear If you use front and rear you can easily and quickly select one of two currents The DMM will Autorange unless you override it by selecting a range You can choose the number of digits displayed using the DIGITS buttons Be sure to select DC I or AC I to measure DC and AC current See User s Guide page 216 for the Burden Voltage for each current range
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