How to detect the quality of the sensor? Introduce several effective methods

Date：2022-06-21 17:20:00 Views：4314

Nowadays, the application of sensors is very common. There are many sensors in many scientific, industrial, medical and service fields. In case of sensor failure, we need to detect the sensor to determine where the failure occurs. There are many sensor detection methods. This paper has collected and sorted out some data, which is expected to be of great reference value to all readers.

1、 Fault symptom judgment method

It is the most intuitive and simple method to solve vehicle faults and judge whether sensors are good or bad by using experience judgment based on fault symptoms. However, it has two disadvantages: first, it takes a long time to accumulate experience, and it is impossible to reach a very high level in a short time; Second, the accuracy of judgment results is low and the possibility of misjudgment is high.

2、 Decoding detection method

Decoder is usually divided into original decoder and non original decoder. Reading and clearing the fault code is the main function of the decoder, so it is easy to determine the general direction and location of the fault, providing a direction for the detection and troubleshooting of the sensor. However, the following points should be noted:

1. not all faults have fault codes.

2. the meaning of the fault code shall be clarified, whether it is sensor or actuator fault or line fault; Line fault shall be distinguished from short circuit or open circuit, short circuit or open circuit with power supply, short circuit or open circuit with grounding, etc.

4. it is necessary to find out whether it is a historical fault code or a current fault code and the number of occurrences of the fault code. If it is a historical fault code, it means that the fault occurred earlier and does not appear now, but there is a certain amount of memory in the ECU; The current fault code indicates that it is a recent fault, and most of the current faults are closely related to the current system.

5. when the fault code cannot be read but the vehicle still has fault symptoms, the data stream of the decoder shall be used to conduct in-depth analysis and judgment on the sensor and actuator.

6. after troubleshooting with reference to the fault code, the decoder shall be used to clear the fault code, that is, the fault code memory shall be cleared from the ECU internal memory, and after the engine has been running for a period of time (if possible, the road test can be carried out), then the decoder shall be used to test whether similar fault phenomena will occur, or the same fault code shall be stored.

7. it is not recommended to remove the negative pole of the battery to clear the fault code.

3、 Test lamp test method

The test lamp includes self-made test lamp and special test lamp for detection; You can bring your own power supply or no power supply. The self-made test lamp can be made of light-emitting diodes (LEDs) connected in series with 300~500 Ω resistors. Its form is shown in the following figure. The test lamp mainly has the following functions:

1. check whether the sensor, electronic control element body or connecting circuit is on or off.

2. check whether the sensor reference voltage supply is normal.

3. according to the stroboscopic signal of the LED of the test lamp, you can check whether the sensor has pulse output or whether the ECU has execution signal output.

4. for vehicles with manual code adjustment and self diagnosis function, read the fault code manually.

4、 Multimeter test method

In addition to manual code adjustment and fault code reading in the early stage, the use of a pointer multimeter is generally not advocated. Even when detecting some components, especially semiconductor components and related ECU circuits, it is emphasized that a digital multimeter must be used. This is because the digital multimeter has large impedance and small current passing through components, which can avoid burning other components during measurement.

1. resistance detection method

The resistance detection method is mainly used to detect the resistance of variable resistance, potentiometer sensor and magnetoelectric sensor. For semiconductor components, it is generally necessary to compare with the measured values of standard components to draw a conclusion.

2. voltage detection method

For the active sensor, because it can generate voltage when it works, the voltage detection method can be used to detect whether the sensor works normally. For example, oxygen sensor, magnetoelectric crankshaft position / camshaft position sensor, knock sensor, etc.

3. current detection method

The current detection method is mainly used to generate a new type of integrated circuit sensor with current modulation signal

5、 Oscillograph method

The oscilloscope is mainly used to display the voltage waveform of input and output signals in the control system, so that the maintenance personnel can judge the fault of the electronic control system according to the waveform analysis. Oscillograph has faster display speed than general electronic equipment. It is the only detection instrument that can display instantaneous waveform. It is an important equipment in fault diagnosis of electronic control system. Oscilloscope detection is the most accurate and intuitive detection method, which can display the output current or voltage of the sensor in the form of waveform. It is also the development direction of the detection of electrical components such as sensors.

6、 Simulation method

The simulation method is used to simulate the input signal of the automobile computer with the sensor simulation tester under the condition that the sensor connection is disconnected and other lines are normally connected, so as to work instead of the sensor, and judge the quality of the sensor according to the disappearance or existence of the fault phenomenon. This kind of simulation method can simplify the analysis process, shorten the diagnosis time and reduce the economic losses caused by the blind replacement of parts.

7、 Substitution method

The substitution method is to find the fault of the suspect sensor by trial replacement, which is also called trial replacement method. The substitution method can determine the fault location or reduce the fault scope, but it may not be able to determine the fault cause. When repairing the sensor, it is better to use the sensor of the same model, the same model, and the same specification to temporarily replace the sensor in question. If the fault phenomenon does not disappear after replacement, it indicates that the fault is not caused by the sensor, and the fault is in other parts.

The detection method of the sensor is not unchanging. It often needs to make modifications according to the different characteristics of the detected sensor, so that there will be more ways to solve the problem. In fact, it is more important to absorb knowledge and experience in practice and improve the shortcomings of existing methods.