Application of Tektronix Digital Multimeter in the Automotive Industry

3. Detection of automobile engine shaking and black smoke. The oxygen sensor installed in the front of the exhaust pipe 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 and rich mixture. Its electromotive force is fed back to the 28th and 10th pins of the computer (ECU) to control gasoline injection and achieve the best air-fuel ratio (14.7). In order to shorten the heating process of the oxygen sensor, the sensor is electrically heated. See Figure 2 for the specific method of checking and measuring the oxygen sensor on the vehicle (a high-impedance digital multimeter should be used when measuring). During the detection, it was found that the electromotive force was zero, indicating that the sensor was damaged, so that the computer mistakenly received the "lean" mixture signal, resulting in increased fuel consumption and black smoke from the exhaust. After replacing it with a new sensor, the engine operation returned to normal, so the degradation was eliminated.

4. Inspection of the automobile computer control system. When inspecting the automobile computer system, it is strictly forbidden to disconnect the battery line when the engine is running to prevent the generator from losing load and causing excessive voltage to damage the computer; at the same time, because most automobile engine computers have permanent power supplies, it is forbidden to disassemble the computer before disconnecting the battery to avoid generating self-inductance potential and causing damage to the computer, and it is strictly forbidden to plug and unplug computer-related components with inductive properties when the engine is running. When inspecting the computer board and related components, the corresponding computer terminal connected to the injector should be found according to the circuit diagram or the direction of the actual line, and then the on-off block of the digital multimeter should be used to start from the determined computer terminal and search along the computer's printed circuit inward until a certain transistor or transistor row is found to test whether there is any damage. This can quickly test the fault of the computer control system.

5. Fault detection and repair of automobile air conditioning failures. In the automobile air conditioning system, whether it is manually controlled or automatically controlled, the disconnection and engagement of the compressor electromagnetic clutch are generally controlled by the computer. Therefore, a considerable number of automobile air conditioning system failures occur in the computer. (1) When testing the computer system of the automobile air conditioner, use the measurement on-off block of the digital multimeter to start from the determined air conditioning control terminal and search inward along the computer's printed circuit little by little until a certain transistor or transistor row is found to test whether there is any damage. (2) When the air conditioning operation panel is set to the air conditioning cooling operation state, use the voltage block of the digital multimeter to connect to a base line to be confirmed, turn on the A/C switch, it should display 5V, and when the switch is turned off, it should display 0V. Use this method to test the two wires, and repeatedly confirm that the one that meets the conditions is the base. When confirming the emitter, if it is a transistor row, the emitter is usually at the two ends of the row. Use the multimeter's measurement switch to connect one end to the ground terminal of the computer and the other end to the ground terminal of the row. The pin that can be turned on is the emitter of the transistor. (3) Remove the roughly determined transistor from the circuit board and use the multimeter's diode measurement block to measure the properties of the transistor. (4) Select the digital multimeter's transistor measurement block, insert the base of the transistor into B, and the other two pins into C and E respectively. If the displayed value is between 200 and 300, it proves that the pins are inserted correctly. C represents the collector and E represents the emitter. Then determine whether the transistor is PNP or NPN. P is the positive pole and N is the negative pole. (5) When the selected transistor is to be soldered to the circuit board, use the digital multimeter to measure the on-off position, use the positive and negative test leads to touch the collector and emitter of the transistor, connect the base to the base control line of the circuit board, turn on the air conditioner, and see if the multimeter shows conduction. If it is, it proves that the transistor can be used. After the soldering is completed, use a multimeter to measure that the pins should not be connected to each other. Through the above steps, the car air conditioner can be repaired quickly.

From what has been explained above, it can be seen that the super-functional data communication true RMS multimeter (FT365/FT368) launched by Feisi Technology is still widely used in the automotive industry. Of course, there are other applications that are not mentioned in this article. I believe that the practical application of digital multimeters in the automotive industry will continue to be discovered.