How To Use A Cen Tech Digital Multimeter
Cen-Tech makes several digital multimeters. However, you don’t have to follow separate instructions for each. You can use any of the seven functions if you are familiar with the 98025 model. This model can measure AC and DC voltage, current, resistance and it can also test transistors, diodes and batteries.
Get ready to use the Multimeter
The main selector wheel is located on the front end of the multimeter. This wheel allows you to select the function and the sensitivity you want for the measurement. On the bottom right, you’ll see three jack inputs in a vertical arrangement. These are marked from top to bottom – 10ADC VOmA, COM. These jacks can be used to fit the leads. You’ll find a multipin transistor/hFE jack on the left for testing transistors. A button to turn the On/Off switch is also visible. This button will turn on the LED display.
Measurement of Voltage and Current
Rotate the selector until it points to 750 in AC voltage section (ACV). The red lead should be plugged into the jack marked “VOmA” and the black lead into jack “COM”. Note the reading by touching the exposed wires in the circuit that you are testing. To get a better reading, change the AC voltage section selector to 250 to see if it is lower than 250 volts.
You can measure DC voltage by removing the red lead from the jack marked VOA and the black lead from the jack mark COM. The dial will then be turned counterclockwise until it reaches the 1000 setting in DC voltage section (DCV). The leads should be touched to determine the reading. Move the dial to the setting that gives the lowest reading. Move the dial to the next setting if the reading is below 20 To get the best reading, keep turning the dial until it reaches 200 mV.
Switch the red lead to the 10 ADC Jack and the black lead to the COM Jack. This will measure current. The dial should be set to 10 A (10A), the meter must be on, and the lead to the circuit wires must be touched. Note the reading. If the reading is below 0.2 am, turn off the meter and place the red lead in the VmA Jack. Next, move the dial counterclockwise to reach the 220m setting of the DC amp (DCA). Take another reading by turning on the meter. To increase the accuracy of your reading, continue turning the dial clockwise (all the way to 200 u, if necessary).
Measuring Resistance & Continuity
The resistance measurement unit must supply a small current. Make sure that the voltage function is enabled in the circuit to ensure the meter reads 0. The red lead should be inserted in the VOmA jack, and the black lead into COM. Turn on the multimeter, and move the selector towards the 200 position in O. Make sure you touch the leads together before taking a measurement. Note the reading by touching the leads to the exposed wires. Turn the dial counterclockwise if the reading is 1. Continue turning the dial until the reading is different than 1.
To test continuity, you can use the resistance function. Adjust the dial to the 2000k position of the ohm section, and measure the circuit like you would for resistance. The circuit is considered open if the reading is 1. Any reading other than 1, indicates that the circuit is closed.
Test Diodes, Transistors and Batteries
The multimeter can be used to measure the voltage drop across a diode. This can be done to compare it with the specifications of the diode and to determine if it is still working. Turn the dial to locate the diode section at the 6 o’clock position, next to the lowest setting of the ohm section. Inject the red lead into VOmA jack, and the black lead into COM. Turn on the meter. The reading is in millivolts. Touch the red and black leads at the terminals of the diode. If the reading is 1, you can reverse the leads and try again.
This meter can be used to test 9V, D, C, AA, and AAA batteries. To the right of ACV, turn the dial to the battery section. Turn on the meter by inserting the red lead in the VOmA jack, and the other into the COM jack. Note the reading by touching the red lead to its positive terminal and the black lead towards the negative. This function is not suitable for testing 6V and 12V vehicles batteries. Instead, use the voltmeter.
To test a transistor turn the dial to hFE, which is to right of the diode setting. The transistor should be plugged into the multipin NPN/PNP connector. The transistor manual may be helpful in determining the correct orientation. Turn on the meter and take a note of the reading. Compare it with the specifications for the transistor.
Also Read: What Are Vet Techs