A liquid level sensor (static pressure level gauge/liquid level transmitter/liquid level sensor/water level sensor) is a pressure sensor used to measure liquid levels. Static pressure input type liquid level sensor (level gauge) is based on the principle that the measured liquid static pressure is proportional to the height of the liquid. It uses an isolated diffusion silicon sensitive element or ceramic capacitive pressure sensitive sensor to convert the static pressure into an electrical signal. After temperature compensation and linear correction, it is converted into a standard electrical signal (usually 4-20mA/1-5VDC).

In the production processes of daily chemical products, food and beverage, pharmaceuticals and other industries, liquid level monitoring is indispensable. The importance of liquid level sensors is becoming increasingly prominent, and even directly affects the quality of products. Only by correctly understanding the wiring method of the liquid level sensor can errors in the operation of the liquid level sensor be reduced. Otherwise, it is easy to cause damage to the liquid level sensor and affect the accuracy of measurement. Below, we will introduce how to wire the liquid level sensor.

Liquid level sensor is a common sensor for measuring liquid level position, which converts the height of the position into an electrical signal for output. The liquid level sensor is a modular circuit with advantages such as acid resistance, moisture resistance, shock resistance, and corrosion resistance. The circuit contains a constant current feedback circuit and an internal protection circuit, which can ensure that the output current does not exceed 28mA. Therefore, it can reliably protect the power supply and prevent damage to the secondary instrument.

Liquid level sensors typically output signals with currents of 4-20mA, 0-20mA, or voltages of 0-5V, 1-5V, 0-10V, etc. The current type is usually a two-wire or four wire system, while the voltage type is a three wire system output. At present, many do not have a 24VDC power supply, most of which are 10V. Some transmitters with high power consumption cannot be driven by a 10VDC power supply, so they can only be powered by an external 24VDC power supply. In this way, the liquid level sensor has four wiring terminals: power supply+, power supply -, feedback+, and feedback -.

Current type two-wire connection ratio for liquid level sensor wiring: power supply+=power supply+; Signal+==feedback+, power supply -==feedback -. If remote transmission is not required, only 24V voltage+needs to be connected. If remote transmission is needed, a circuit needs to be formed, such as 24V+connected to pressure gauge+, pressure gauge - connected to 4-20mA+, 4-20mA - connected to 24V -. There may be terminals in the middle, please refer to the circuit diagram.

Voltage type three wire wiring method for liquid level sensor wiring: power supply+=power supply+; Power Supply - (Signal -)==Power Supply -; Signal+==Feedback+, Power - (Signal -).

Four wire wiring method for liquid level sensor: power supply+==power supply+; Power Supply -==Power Supply -; Signal+==Feedback+, Signal -==Feedback -.

Some people may ask why the principle of liquid level switch and liquid level sensor is the same, and why the wiring method of liquid level switch is different? That's because the liquid level switch is a controller that opens the drain or inlet valve based on the signal output of the liquid level sensor to maintain a constant water level. It can also be said that the output of the liquid level switch is a switch signal. The liquid level switch first determines the height of the liquid level and outputs a switch signal based on this height. And the liquid level sensor converts the height of the liquid level into an electrical signal for output. We can process electrical signals, such as connecting them to PLCs, data collectors, or professional displays to output the height of the liquid level. Also, although the principles of the liquid level switch and the liquid level sensor are the same. However, the liquid level switch is a switch control circuit, while the liquid level sensor is equivalent to a circuit component used for voltage and current conversion.