What are the problems should be paid attention to when using automobile digital multimeter?

Last Update Time: 2019-03-08 11:15:46

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.

 

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.

 

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.

 

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.

 

 

 

This article is from Allicdata Electronics Limited. Reprinted need to indicate the source.