Make sure you set the voltage settings for AC or DC properly or you risk shorting the meter. Household current, air conditioner and heater current, and any current that powers a device such as a refrigerator is AC current even if it is produced by a battery-operated generator. Current that is produced by a wall outlet adapter at the power plug is DC current, as are power produced by the power supply of your computer and the power produced by your car or boat battery lighter socket.
The Sperry DM-201A is a four-function multimeter that tests the voltage and resistance of AC and DC circuits and power sources, as well as the condition of diodes. This model, which is discontinued as of this writing, has an easy-to-read digital display and requires a 9-volt battery for operation. You change the setting of the central dial and the positions of the test leads in order to select between the four testing functions of the DM-201A.
Remove the test leads and turn the main selector dial so that the dot on the dial handle points to the "Off" (top central) position on the multimeter housing menu. Turn the device over so that the display is facing upside-down on a work surface or in the palm of your hand.
Remove the four housing screws and open the back case. Snap the 9-volt battery that is included with your multimeter, or a fresh alkaline nine-volt battery, onto the battery connector so that the crimped end of the connector is clamped tightly onto the smooth terminal of the battery, and vice versa.
Reinsert and tighten the screws.
Insert the black (negative) test lead into the "Com" jack located in the lower middle of the unit, below the dial, and the red (positive) lead into the "V-Ω" jack at the lower right of your multimeter. Connect the two ends of the leads together.
Move the range selector dial through the following settings:
600DCV 200DCV 20DCV 2DCV 200 2K 20K 200K
and make sure that the digital display reads 000, 00.0, 0.00, .000 for the first four settings and 1_ ., 1.,1. and 1_ _. for the last four settings, respectively. Send your multimeter in for warranty service if you see any other results for the test readings.
Proceed to test your circuit or equipment as needed so long as all test readings match those listed above.
Check the ratings that are posted on your electrical fixtures or appliances to make sure that voltage does not exceed 600 volts AC or DC. If it does exceed this limit, do not attempt to test the voltage with your Sperry DM-210A.
Plug the black test lead into the "Com" jack at the center of the three jacks located at the bottom of your meter, and insert the plug of the red test leads into the rightmost jack, which is labeled "V-Ω" (volts-ohms).
Set the selector dial to the "600ACV" or "200DCV" position, depending on whether the circuit or device you are testing is AC or DC.
Touch each of the two leads to one of the terminals or wires that supplies current to the circuit you are testing. Avoid touching sources of high voltage with any part of your body and do not touch the metal parts (probes) of your meter leads.
Note the reading in the LCD display window of your multimeter. If it is below 200 volts AC or 20 volts DC, turn the dial to the left so that you choose the next lowest setting for the type of voltage you are testing. This is 200V AC or 20V DC. Note the reading again. For AC circuitry, this is the final reading. For DC voltage, if it is below 2 volts DC then turn the dial to the left again for the 2V DC setting and note the final reading.
Remove the leads from the circuit wires or terminals. Turn the meter off and remove the leads from the jacks for storage.
Testing Resistance and Diodes
Insert the black test lead into the "Com" jack at the bottom center of your unit below the selector dial. Plug the red test lead into the "V-Ω" terminal at the bottom right of your meter.
De-energize the circuit or diode you are about to test by turning all power off and discharging any residual power.
Turn the main selector switch to the ohm (Ω) range that is necessary for operation of the circuit or diode you are testing. Check your owner's manual for the proper range if you are testing circuits or diodes in a piece of electronic equipment or an electric appliance.
Connect each of the test leads to the leads or terminals of the device or part being tested, making sure to observe proper polarity; the black lead is negative and the red lead is positive. Connect the red lead to the anode of a diode and the black lead to its cathode.
Note the reading. A blank reading means that the reading is higher than the range you selected. Turn the dial to the right until you get a proper reading.
Make sure that the red lead is securely connected to the anode of your diode and check the reading again if you obtain a reading of  when testing a diode. If  appears in the LCD screen of the meter once again, then replace the diode as it is clearly defective. Repeat the test procedure on the replacement diode before you solder it or otherwise connect it to your circuit board or device.
Take the leads off the circuit wires or terminals or diode leads. Turn the meter off and remove the test leads from the jacks for storage.
John DeMerceau is an American expatriate entrepreneur, marketing analyst and Web developer. He now lives and works in southeast Asia, where he creates websites and branding/marketing reports for international clients. DeMerceau graduated from Columbia University with a Bachelor of Arts in history.