Apr 12, 2014 This is a review of the Harbor Freight Cen-Tech 7 Function Digital Multimeter, Item # 6. The Cen-Tech Seven Function Digital Multimeter Model 90899 is an inexpensive, yet fully-featured device that you can use to measure the strength and efficiency of electrical circuits. This model features the ability to test for AC voltage, DC voltage, DC amperage and resistance (ohms), as well as functions for testing the strength and condition of diodes, transistors and dry cell batteries. It is sold with the two leads that you need to test your circuits and all you need to do to change functions is to adjust the dial. ![]() Testing AC voltage • Turn the main dial so the dot on the knob points to '750' in the 'ACV' section of the selector menu at the centre of the unit if you do not know at all what the voltage of your circuit is, or set it to '250' slightly to the right if you know that your circuit carries less than 200 volts. • Plug the red lead into the centre jack, which is marked 'VΩmA' and the black lead into the bottom jack, which is marked 'COM.' Switch your multimeter 'On' by sliding the switch under the main dial to the right. • Touch the exposed wires that supply the current you are testing simultaneously and carefully with the leads, or insert the leads into your wall outlet so that they touch the metal contacts. • Check the reading that appears on the LCD screen above the selector dial and note it, or turn the dial one stop to the right to the '250' setting to get a more accurate reading if the initial voltage reading is less than 200. ![]() • Turn your Cen-Tech 90899 off. Remove the test leads and store the device and leads together in a convenient place for future use. DC voltage measurements • Turn the main selector so that the dot points to the '1000' setting in the DCV section, slightly to the left of the centre of the selection menu. • Plug the red lead into the centre jack, which is marked 'VΩmA' and the black lead into the bottom jack, which is marked 'COM.' Switch your multimeter 'On' by sliding the switch under the main dial to the right. • Touch each of the wires that supply the current you are testing with each of the leads. • Note your reading as it appears on the LCD meter screen and if it is less than 200, turn the dial to the left so that the dot points to 200 volts DC. Cara menghitung bilangan biner. Take another reading and if it is less than 20 repeat the reading process after you turn the dial one more stop to the left to the 20 volts DC setting. Follow this reading with another reading after turning the dial yet another step if the reading is less than 2 volts -- 200m, 2,000 millivolts, as per the setting -- and take a final reading after turning the dial one more stop to the left, to the 200m setting, if the reading is less than 200 millivolts. • Turn the multimeter off and remove the leads for storage; storing the leads and meter together is recommended for convenience. DC current (amperage) measurements • Turn the main dial so the dot on the selector switch points to the '10 A' setting, which is located at the lower right of the selector menu, below the DCA selection list. • Plug the red lead into the top jack, which is labelled '10 ADC.' Connect the black lead to the bottom jack marked 'COM.'
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