In the production processes of daily chemical products, food and beverages, and pharmaceuticals, liquid level monitoring is indispensable, making liquid level sensors increasingly important and even directly affecting product quality. Only by correctly understanding the wiring method of liquid level sensors can errors be reduced during operation; otherwise, the sensor can easily be damaged, affecting measurement accuracy. Below is an introduction to how to wire a liquid level sensor.
A liquid level sensor is a common sensor for measuring liquid level, converting the height of the liquid into an electrical signal for output. Liquid level sensors are modular circuits with advantages such as acid resistance, moisture resistance, shock resistance, and corrosion resistance. The internal circuitry includes a constant current feedback circuit and internal protection circuitry, ensuring that the maximum output current does not exceed 28mA, thus reliably protecting the power supply and preventing damage to secondary instruments.
Liquid level sensors typically output current signals of 4-20mA or 0-20mA, or voltage signals of 0-5V, 1-5V, or 0-10V. Current-type sensors usually have two-wire or four-wire outputs, while voltage-type sensors typically have three-wire outputs. Currently, many sensors do not have a 24VDC power supply; most are 10V. Some high-power transmitters cannot be driven by a 10VDC power supply, so an external 24VDC power supply is required. This results in four terminals for the liquid level sensor: power supply +, power supply -, feedback +, and feedback -.
For liquid level sensor wiring, the current-type two-wire connection method is as follows: Power supply + == Power supply +; Signal + == Feedback +; Power supply - == Feedback -. If it is not for remote transmission, simply connect to 24V voltage + and -. If it is for remote transmission, a circuit needs to be formed. For example, connect 24V + to pressure gauge +, pressure gauge - to 4~20mA +, and 4~20mA - to 24V -. There may be terminals in between, so you need to refer to the circuit diagram.
The voltage-type three-wire wiring method for liquid level sensors is as follows: Power+ == Power supply+; Power-(signal-) == Power supply-; Signal+ == Feedback+, Power-(signal-).
Four-wire wiring method for liquid level sensor: Power + == Power supply +; Power - == Power supply -; Signal + == Feedback +; Signal - == Feedback -.
Some people might ask why the wiring methods for level switches and level sensors differ even though they operate on the same principle. This is because a level switch is a controller that opens a valve to release or release water, maintaining a constant water level, based on the signal output from a level sensor. In other words, a level switch outputs a switching signal; it first determines the liquid level and then outputs a switching signal accordingly. A level sensor, on the other hand, converts the liquid level into an electrical signal for output. This electrical signal can be processed, for example, and connected to a PLC, data acquisition unit, or professional display to output the liquid level. Furthermore, although level switches and level sensors operate on the same principle, a level switch is a switching control circuit, while a level sensor is essentially a circuit component used for voltage and current conversion.
