Feith digital multimeter application in the automotive industry

Digital multimeter is one of the indispensable products in the field of electronic testing and maintenance, and its application is more and more extensive. A digital multimeter is a measuring instrument that uses the principle of analog-to-digital conversion to convert the measured data into digital quantities and displays the results in digital form. Compared with the analog multimeter, the digital multimeter has the advantages of high precision, high speed, large input impedance, digital display, accurate reading, strong anti-interference ability, and high degree of measurement automation. Therefore, the digital multimeter is widely used and is favored by users.

Shenzhen Festec Technology Co., Ltd. launched a series of high-end digital multimeter products, including super-functional data communication true RMS multimeter (FT365/FT368), industrial data communication true RMS multimeter (FT335/FT338), wide frequency response True-RMS multimeter (FT212/FT215/FT217) and auto-ranging multimeter (FT163/FT168/FT6/FT8).

With the development of the automotive industry, more and more electrical devices are now being used in automobiles. When troubleshooting the electrical parts of automobiles, multimeters are one of the most commonly used automotive electrical maintenance tools for testing voltages. Current and resistance. The super-functional data communication true-rms multimeter (FT365/FT368) introduced by Fission Technology has been widely used in the automotive industry. The following describes several examples of automotive electrical faults to illustrate the application of digital multimeters.

1. Anti-lock brake system (ABS) detection. Due to the influence of traffic conditions such as roads, climate, traffic management and driving qualities, the vehicle must be constantly braked and emergency braked. In an emergency situation, when the brakes are slammed, the brake force is immediately maximized and the wheels are locked. If the front wheel is locked, the steering will fail; if the rear wheel is locked, the car will tend to slip or flick. If you find that the wheel speed sensor in the brake system is not working properly, use a digital multimeter to measure the resistance of the coil. The resistance is largely broken, and the resistance is short-circuited. The sensor heads need to be replaced.

2, the car's own flameout fault detection. When overhauling the EFI engine, maintenance personnel often overlook the inspection of power supply and ground wire. The computer must provide sufficient voltage and good grounding during normal operation. Other electronic controllers should also meet the same conditions. The line uses its own housing, there is no green ground, which should be taken seriously during the inspection, and in some cases, the power supply is poor, the problem is mostly on the power supply line. For this, use a digital multimeter to check the battery voltage during the test. With the computer, the electronic control voltage is the same. In short, if the computer checks the power supply and ground wire in the case of outputting normal code, it may be able to find the real cause of the failure.

3, automobile engine jitter black smoke detection. The oxygen sensor installed in the front of the exhaust muffler is actually a solid battery. In normal operation, it can emit 0.25-0.85V electromotive force, corresponding to the combustion condition of lean rich gas mixture. The electromotive force is fed back to the 28th and 10th feet of the computer (ECU) to control the gasoline injection to achieve the best air-fuel ratio (14.7). In order to shorten the heating process of the oxygen sensor, the sensor is electrically heated. Refer to Figure 2 for the specific method of measuring and measuring the oxygen sensor enthalpy on the vehicle (measurement should use a high-impedance digital multimeter). During the test, it was found that the electromotive force was zero, indicating that the sensor was damaged, which caused the computer to misreceive the “lean” mixture signal. As a result, the vehicle’s fuel consumption increased and the exhaust gas emitted black smoke. Replaced by a new sensor, the engine returned to normal operation, so the drop was eliminated.

4, the car computer control system testing. When testing automotive computer systems, it is strictly forbidden to disconnect the battery line while the engine is running, to prevent the generator from losing the load and causing excessive voltage damage to the computer; at the same time, since most automotive engine computers have permanent power, it is forbidden to disconnect the battery. Before disassembling the computer, so as to avoid the self-induction potential caused by computer damage, and prohibit the insertion and removal of the computer with the inductance of the components when the engine is running. When detecting the computer board and related components, the corresponding computer terminal connected to the injector should be found according to the circuit diagram or the actual line direction, and then use the digital multimeter's break-through to start from the determined computer terminal along the printed circuit of the computer. Look inside until you find a transistor or transistor bank and test for damage. After this, you can quickly test the fault of the computer control system.

5, fault detection and maintenance of automotive air conditioning faults. In the air-conditioning system of a car, whether it is manual control or automatic control of the air-conditioning, the cutting off and the engagement of the electromagnetic clutch of the compressor are generally realized by the computer. Therefore, in the breakdown of the automobile air-conditioning system, a considerable part of the faults appear on the computer. . (1) When testing the computer system of an automobile air conditioner, use a digital multimeter to measure the breaks, search from the determined air conditioning control terminal, and trace it in little bits along the printed circuit of the computer until it finds a certain transistor or triode. Rows, test for damage. (2) In the air conditioning operation panel installed in the air conditioning cooling operation, using a digital multimeter voltage block connected to a base line to be confirmed, open the A / C switch, which should display 5V, close the switch should show 0V. Use this method to test the two wires and repeatedly confirm that the base is met. When confirming the emitter, if it is a triode row, its emission is very much at both ends of the row, and the end of the measurement through the multimeter is connected to the ground of the computer, and the other end is connected to the ground terminal considered to be a row. The pass pin is the emitter of the transistor. (3) Remove the roughly determined transistor from the circuit board and use the multimeter's diode to measure the triode's properties. (4) Select the transducer of the digital multimeter, insert the base of the triode into B, and insert the other two legs into C and E. If the displayed value is between 200 and 300, verify that the pin is inserted, C represents the set Electrode, E represents the emitter. Then determine whether this transistor is PNP type or NPN type. P is positive and N is negative. (5) When the selected transistor is to be soldered to the circuit board, use a digital multimeter to measure the breakage, use the positive and negative probes against the collector and emitter of the transistor, and control the base and the base of the circuit board. Connect the line, turn on the air conditioner, and see if the multimeter shows continuity. If it turns on, prove that this transistor can be used. After the welding is completed, the multimeter should be used to measure each pin should not be connected to each other. Through the above steps, you can quickly repair the car air conditioner.

From the above-mentioned point of view, the application of the super-functional data communication true RMS multimeter (FT365/FT368) introduced by Fiss Technology in the automotive industry is still very extensive, of course, there are other applications that are not mentioned in this paper. It is believed that the practical application of the digital multimeter automotive industry will continue to be discovered.