What is the relevant knowledge of sensors?
Sensor power up
The sensor is an active device used to measure current and voltage signals. An external DC power supply is required for the sensor to work.
1) After the power supply of the sensor is turned on, the measured signal on the primary side is passed in.
When the measured signal is input, the corresponding output of the sensor will be output. This output signal will change with the change of the measured signal on the primary side.
If the power-on sequence of the primary and secondary sides is reversed, the sensor may be damaged. I hope that you must pay attention to it in practice!
2) After the wiring on the secondary side of the sensor is correct, first switch on the DC power supply for the sensor.
For dual power sensors, the power supply is DC +/- 12V, +/- 15V or +/- 24V.
If it is a single-supply sensor, the power supply is DC + 5V.
The DC power supply of the sensor should be stable, and the fluctuation should be within +/- 5%. Too low or too high will affect the normal operation of the sensor, too high voltage may damage the sensor.
After the sensor's DC operating power is connected, the sensor is in standby mode. At this time, the secondary output will have a small signal output, as long as it is within the range allowed by the specification, it is normal.
Under the application of new technology, the sensors are calibrated and calibrated by laser resistance adjustment and software resistance adjustment. However, there are still some sensors on the market that use potentiometers. Usually these exposed potentiometers are made by the manufacturer at the factory For sensor calibration, it is used to adjust the zero point and accuracy of the sensor. After adjustment, it is fixed with red glue to prevent the potentiometer from being accidentally touched to change the resistance value. Then do not adjust the exposed potentiometer at will, otherwise it will affect the measurement accuracy of the sensor.
Selection of load resistance
Load resistance refers to the resistance connected to the output end of the sensor. Usually, the output current signal will limit the maximum value of the load resistance, and the minimum value of the load resistance will be limited when the voltage signal is output.
1) Current output type sensor
When the output signal of the sensor is a current signal, it usually needs to be converted into a voltage signal during sampling. At this time, a measurement resistor needs to be connected between the output terminal of the sensor and OV. The selection of the measurement resistance is limited by the size of the sensor's power supply voltage and the size of the measured signal, and it cannot be selected at will.
Under the same power supply voltage, the measured resistance value will affect the range of the primary signal that the sensor can measure. The smaller the resistance value, the larger the measured signal, the larger the measurement range, the larger the resistance value, and the smaller the measured signal. , The smaller the maximum measurement range. However, it should be noted that the measurement resistance value of some sensors cannot be reduced infinitely, otherwise the sensor will be damaged.
Usually in the specification, the manufacturer will indicate the number of ranges to measure the resistance, including the minimum and maximum values. As long as the value of this resistor is within the range specified in the specification, the sensor can work normally and meet the parameter indicators promised in the specification.
2) Voltage output type sensor
When the output signal of the sensor is a voltage signal, in order to ensure that the connection of the load resistance does not affect the attenuation of the output voltage value of the sensor, there is a limit on the minimum value of the load resistance.
The manufacturer will indicate the size of the load resistance in the specification, which is usually in the thousands of ohms. Therefore, when the output of the sensor is connected to the subsequent circuit, the equivalent resistance must be greater than the allowed load resistance. Otherwise, the output value of the sensor will decrease.
The above is a discussion of the problems in the use of sensors. With most sensors, if special circumstances are encountered, they need to be treated specifically for different manufacturers and different models. In practical applications, the correct treatment and use of sensors can do more with less in the work of system engineers and commissioning engineers.
If you want to know more, our website has product specifications for sensor， you can go to ALLICDATA ELECTRONICS LIMITED to get more information