The Cen-Tech 7 function multimeter is an inexpensive meter readily found in a multitude of stores for under $10. It is a small battery-operated, pocket-style meter that will work for the individual that occasionally needs the use of a multimeter. The multimeter provides accurate digital readings for AC/DC voltage, DC current, resistance, transistor tests, diode tests and battery tests.
Turn on the meter. Put the black meter lead in the lower meter connection marked "COM," and the red lead in the middle meter connection marked Volts/Ohms/mA. Connect the leads to the circuit you are measuring. To measure AC voltage, turn the selector to the correct AC voltage range. Read the voltage.
Turn the middle selector switch to "1000 DCV." Read the DC voltage measurement. Continue to decrease the voltage range until you obtain a full-scale reading without going over the maximum range voltage.
Place the meter in series with the device or component to measure amps. Place the red lead in the top meter lead connection marked "10ADC." Turn the center selector switch to the "10A" position. Read the direct current amperage. If less than 200 milliamps, turn the center selector to "200m" and move the red lead to the Volts/Ohms/mA, then retest the circuit until you obtain a full-scale reading without going over the maximum range current.
Turn the center selector to "200 ohms." The screen should read "1" for infinite resistance. Touch the leads to the component you are measuring. Read the resistance. If the meter still reads "1," turn the center selector to the next higher resistance range and remeasure until a "1" is no longer displayed. Read the resistance.
Determine what type of transistor you are testing by looking up the number and finding it on a specification sheet. An NPN transistor would go into the NPN side of the tester with the emitter in the E hole, the collector in the C hole and the base in the B hole. A PNP transistor would go into the PNP side with the emitter, collector and base in their respective holes. Turn the center selector to hFE. Read the hFE and compare to the data sheet.
Turn the center selector to the diode position. Touch the red lead to the anode end of the diode and the black lead to the cathode end of the diode. The reading will be the forward voltage drop. If you obtain the reading of "1," the leads are reversed.
Turn the center selector to the battery position. Touch the red lead to the positive end of the battery and the black lead to the negative end of the battery. For a 9-volt battery, a full charge would be 25 or greater milliamps. For a 1 1/2-volt battery, a full charge would be 4 or greater milliamps.