The correct understanding of the wiring method of the liquid level sensor
will reduce the errors in the operation of the liquid level sensor, otherwise, it will easily lead to the damage of the liquid level sensor and affect the accuracy of measurement. Therefore, the wiring method of liquid level sensor is very important for our use. So how to connect the liquid level sensor? We will introduce the connection method.
The general output signal of a liquid level sensor is current 4-20MA, 0-20MA, or voltage 0-5V, 1-5V, 0-10V, etc. Usually, the current mode is two-wire or four-wire, a three-wire output of voltage. At present, many sensors do not have a 24VDC power supply, most of them are 10V. Some transmitters with high power consumption cannot be driven by a 10VDC power supply, but can only be connected with 24VDC power supply. In this way, there are four terminals in the liquid level: power supply +, power supply -, feedback + and feedback -.
The four-wire connection mode of liquid level sensor: power supply += power supply +; power supply - = power supply -; signal += feedback +, signal - = feedback.
Current-mode two-wire connection mode of liquid level sensor: power supply += power supply +; signal += feedback +, power supply - = feedback-.If you don't need a remote transmission, you only need to connect 24V voltage +, -, if you need the remote transmission, just compose a circuit, such as 24V + pressure gauge +, pressure gauge - 4-20mA +, 4-20mA - 24V - can. Take a look at the circuit diagram to confirm whether there are terminals in the middle.
Voltage-type three-wire connection mode of liquid level sensor: power supply += power supply +; power supply - (signal-) = power supply -; signal += feedback +, power supply - (signal-).
2. The Difference between the liquid level sensor and level switch
The liquid level switch is a kind of controller which can keep the water level constant by opening the valve of discharging or entering water according to the signal output of the liquid level sensor. It can also be said that the liquid level switch outputs a kind of switch signal. The liquid level switch first determines the height of the liquid level and then outputs the switching signal according to the height. The liquid level sensor converts the height of the liquid level into the form of electrical signals for output. We can process electrical signals such as plc, data acquisition or professional display to output liquid level. Although the principle of liquid level switch and liquid level sensor is the same, the liquid level switch is a switch control circuit, and the liquid level sensor is equivalent to the circuit components used for transformer and converter.
The optoelectronic liquid level sensor is a new type of contact point liquid level measurement and control device based on the principle that light reflects and refracts at the interface of two different media. With its simple structure, high positioning accuracy, as well as no mechanical parts, no debugging, high sensitivity, corrosion resistance, less power consumption, small size, and many other advantages, it has been gradually recognized by the market.
1. Since the output of liquid level sensor is only related to whether the photoelectric probe contacts the liquid level or not, it has nothing to do with other characteristics of medium, such as temperature, pressure, density, electrical parameters, etc.,Therefore, the photoelectric liquid level sensor has the advantages of accurate detection, high repetition accuracy, fast response, precise liquid level control, and can be directly installed and used without adjustment.
2. Because the probe of photoelectric liquid level sensor is relatively compact, it can be separately installed in a narrow space for special tanks or containers. In addition, a plurality of photoelectric probes can be installed on a measuring body to make multi-point liquid level sensors and controllers.
3. The liquid level sensor
has high reliability, long life and maintenance-free because all the components inside the sensor are sealed with resin, and there are no mechanical moving parts inside the sensor.