How to use the basic measurement function of automobile digital multimeter?
1.Proper use of basic measurement functions.
Automobile digital multimeter is an ideal instrument for detecting common electronic equipment of automobile, but it must be used correctly, and if it is not used properly, it can not get the correct data. The basic measuring function of automobile digital multimeter is described in Table 1 for reference.
Table 1. Use of basic measurement functions of a digital multimeter for automobiles.
Serial number | Measuring item | Measuring method |
1 | Temperature measuring method | (1) Place the auto digital multimeter item selection switch in the temperature (temp) block and press the function temperature (°c/f) button. (2) The black wire tie-up (that is connecting GND), the probe plug into the temperature measuring jack of the digital multimeter of the vehicle, and then the probe end to be connected to the object to be measured, the number displayed on the digital multimeter display is the temperature being measured. |
2 | Method of measuring bandwidth-to-width ratio | (1). Place the automotive digital multimeter item selection switch in the bandwidth ratio (duty cycle) block. The black wire of the multimeter (i.e. connecting GND), the red frequency-width ratio measurement method line and the signal output end that need to measure circuit are put into the multimeter. (2) Starting the engine to make it run, the frequency-to-width ratio of the pulse signal can be displayed on the digital multimeter display screen of the automobile. |
3 | Method of speed measurement | (1). Put the automotive digital multimeter item selection switch in the rotational speed (RPM) gear. The special plug for speed measurement is inserted into the iron seat hole and the common seat hole, and then the auxiliary accessories of the digital multimeter are sandwiched on the high-pressure ignition line of a certain cylinder of the automobile engine. (2). Starting the engine to make it run, and observing the automobile digital multimeter display screen can show the speed of the engine. |
4 | Method of measurement of starting current | (1). Place the automotive digital multimeter item selection switch in the 400mv (1mv equivalent to 1a current, where the starting current of the starter is measured using a voltage measurement method). The hall current sensor is sandwiched on the battery positive connection wire, the lead is inserted into the multimeter current measuring jack, and then the maximum / minimum function key of the digital multimeter is pressed. (2). After removing the high-voltage conductor in the central socket of the ignition coil (to ensure that the engine will not be started), the engine crankshaft is driven by a starter to turn the crankshaft for 2-5 s. At this time, the data displayed on the automobile digital multimeter display screen is the starting current value.
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5 | Method of measuring signal frequency | (1) Put the automotive digital multimeter item selection switch in the frequency (Freq) block. The black wire (connected to the ground wire) of the iron socket of the digital multimeter, the red wire drawn from the public socket hole of the digital multimeter and the detected signal line are put into the black wire (connected to the ground wire) of the automobile digital multimeter. (2). When the detected circuit is put into the working state, the data displayed on the automobile digital multimeter display screen is the measured frequency. |
6 | Method of measuring the closure angle of the primary side circuit of the ignition coil | (1). Put the automotive digital multimeter item selection switch in the closed angle (dwell) block. The black wire (connected to the ground wire) of the car digital multimeter is connected to the negative pole of the ignition coil from the common socket hole of the automobile digital multimeter, which is connected with the black wire (connected to the ground wire) of the automobile digital multimeter. (2). After starting the engine to make it run smoothly, the data displayed on the digital multimeter display screen is the closing angle of the primary circuit of the ignition coil. |
7 | Method of measuring resistor | (1). Put the automotive digital multimeter item selection switch in the appropriate range of resistance (Ω) block, after correcting the zero point of the meter, the resistor value can be measured. (2). The short circuit and open circuit fault of electrical components and circuits in automobile can find the fault location or cause by measuring resistor of automobile digital multimeter. It must be noted that the electrical resistor must not be measured on line in order to prevent damage to the detection instrument. |
8 | Method of measuring DC voltage | (1). Put the automotive digital multimeter item selection switch at the appropriate measurement range for the DC voltage (V) block, and two test pens are connected to both ends of the measured circuit or component so that the voltage value can be measured. (2). The method of DC voltage measurement can be used to detect the point voltage, signal voltage, power supply voltage, voltage drop on electrical components or parts of automobile circuit, so as to determine the cause or the general position of the fault.
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