What are the problems should be paid attention to when using automobile digital multimeter?
Some problems listed in table 1 should be paid attention to in practical use, although it is very convenient and effective to use automobile digital multimeter to detect the faults of automobile electrical appliances.
Tables 1. The use of automobile digital multimeter should pay attention to problems.
Serial number | Items to be noted | Specific request description |
1 | Familiar with the use of testing instruments. | Before using the automobile digital multimeter, you should familiarize yourself with the use of the testing functions of the meter. Although there are many types of automobile digital multimeter, their detection principle is very similar to the operation method, so as long as they are familiar with the user method of a certain table, There is no problem with the use of other digital multimeter models. |
2 | Exclude the possibility of fuse, wire harness connector anomalies first | Before the automobile digital multimeter is used to detect the faults of automobile electrical appliances, the fuse and wire harness connector in the relevant system of the vehicle should be checked first if they are in good condition. The status of each fuse and harness connector can be checked according to the installation location described in the repaired vehicle maintenance manual to confirm that it is in good condition.
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3 | Eliminate the possibility of insufficient electricity supply. | Check the electrical system's power supply connections (emphasis should be placed on battery positive connections and tie-up wires, where the probability of failure is as high as possible due to poor contact for oxidation) good contact and measurement of the battery's adequacy of electricity, If the supply voltage is less than 11V, the detection error will increase, and even the false detection results will appear. |
4 | The input impedance of the digital multimeter shall meet the requirements. | If the digital multimeter used is used with a lower impedance,that will cause the data detected to be inaccurate and, in severe cases, even cause damage to microcomputer integrated circuits, sensors or other components in the electronic control system. Therefore, before the fault detection, it is necessary to read the manual of the digital multimeter in order to confirm that the value of the input impedance meets the testing requirements. |
5 | The measurement instrument should be properly connected. | The jacks on the digital multimeter panel of the car are marked with polarity marks. When measuring the current, be sure to pay attention to the correctness of the connection between the positive and negative polarity.
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6 | The measuring range should be correct. | In parameter measurement, the selected range should be gradually transformed from a high to a low range, and the best range should be selected according to the observed situation of the measurement, so that the instrument can be prevented from being damaged. Select a range shift, as far as possible at a 1 / 2 position of the full range. |
7 | Power down and then remove the harness. | When detecting electronic controllers, sensors, actuators, it is often necessary to disconnect the harness connector from the control circuit, but it must be done when the power is disconnected. That is to say, the battery negative lap wire should be removed before the connector to disconnect the harness connector of the control circuit, and must not be charged to disconnect the peripheral circuit of the electronic controller. Prevent damage to the electronic controller or related components to correctly distinguish the connector plugs from receptacles. |
8 | Correctly distinguish the connector plug and socket | Harness connectors used in cars are divided into two parts (plugs and sockets)-part connected to the harness of the vehicle and-part connected to electronic controllers, sensors, actuators and other components or components, etc. The two plug together to play the role of circuit connection. Therefore, in the course of fault detection, one must distinguish which part of the connector, in order to prevent errors.
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9 | Prevents high voltage from entering the interior of the electronic controller | When measuring the resistance of each pin of the electronic controller, the common multimeter can not be used to measure it, and high resistance and high precision digital meter should be used. |
10 | Voltage measurement should be carried out with a load. | Multimeter, there must be at least 10MΩ internal resistance, in particular, the higher voltage cannot be introduced to the electronic controller internal to prevent damage to the electronic controller internal components. |
11 | Method for correctly measuring ECU parameters. | Sensors, relays, actuators and other devices used in automobiles are all connected to the electronic control unit ECU through connectors, so they can be measured on the corresponding end-pins of the ECU connector when fault detection is carried out.
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This article is from Allicdata Electronics Limited. Reprinted need to indicate the source.