NBL-L-WLPS Submersible Water Level Transmitter

The NiuBoL NBL-L-WLPS Submersible Water Level Transmitter is an IP68 hydrostatic level sensor designed for continuous liquid-level measurement in tanks, wells, reservoirs, rivers, irrigation systems, industrial pools and other water or liquid monitoring applications.

The transmitter uses a diffused silicon piezoresistive sensing element. The probe is immersed directly in the measured liquid, where hydrostatic pressure changes according to the liquid level. An internal signal-processing circuit converts the pressure measurement into digital level data for transmission through RS485 Modbus RTU.

A vent tube inside the special cable connects the reference side of the pressure sensor to atmospheric pressure, helping compensate for atmospheric-pressure changes. The stainless-steel probe, protective cap, anti-clogging liquid inlet and sealed cable structure are designed for long-term submerged measurement.

NBL-L-WLPS Submersible Level Transmitter Technical Specifications

How the NBL-L-WLPS Submersible Level Transmitter Works

When the probe is submerged below the liquid surface, the pressure-sensitive diaphragm detects the hydrostatic pressure generated by the liquid column above the sensing point.

For a liquid with known density, hydrostatic pressure is related to level by:

P = ρgh

The diffused silicon sensor converts this pressure into an electrical signal. The built-in microprocessor and signal-processing circuit then calculate the level value and transmit it through the RS485 Modbus interface.

Why Does a Submersible Level Sensor Need a Vented Cable?

The NBL-L-WLPS uses a special cable containing an internal atmospheric vent tube. This tube allows the reference side of the pressure sensor to remain connected to atmospheric pressure.

This is important because atmospheric pressure changes independently of the water level. Atmospheric compensation allows the transmitter to determine the pressure produced primarily by the liquid column rather than treating atmospheric-pressure changes as level changes.

NBL-L-WLPS Product Features

Available Measurement Ranges and Accuracy Classes

The NBL-L-WLPS is not limited to one fixed 1000 mm range. Different full-scale ranges can be selected according to the actual liquid depth, and customized ranges are available for special projects.

For product selection, specify the expected minimum and maximum liquid level, measured medium, medium temperature, cable length and required accuracy class.

Installation Methods

The NBL-L-WLPS can be installed vertically, inclined or horizontally depending on the tank, channel or monitoring structure. The sensing end must remain exposed to the measured liquid and should not become buried in sediment.

RS485 Wiring

Two cable-color configurations are documented for the RS485 version. Always follow the wire identification supplied with the actual sensor.

Important: When several RS485 devices share one bus, each device must use a unique Modbus address.

RS485 Modbus Communication Parameters

NBL-L-WLPS Modbus Register Map

Modbus Level Value Example

For example, for a 0–3 m level transmitter configured with three decimal places, if register 0004H returns decimal value 101:

101 × 10^-3 = 0.101 m

The actual decimal position and engineering unit should be read from the relevant Modbus registers rather than assuming one fixed scaling value for every measuring range.

Typical Applications

Common Problems and Troubleshooting

Maintenance and Handling

NBL-L-WLPS Submersible Level Transmitter FAQ

Q1. What principle does the NBL-L-WLPS use?

A1. It uses a diffused silicon piezoresistive pressure sensor to determine liquid level from hydrostatic pressure.

Q2. Is the measurement range fixed at 1 meter?

A2. No. Different measuring ranges can be selected according to project requirements, and customized ranges are available.

Q3. What is the standard power supply?

A3. The supported DC supply range is 10–30 V, with 24 VDC as the typical supply.

Q4. What is the default RS485 baud rate?

A4. The default baud rate is 4800 bps. The communication baud rate can be configured from 1200 to 115200 bps.

Q5. What is the default Modbus address?

A5. The factory default address is 0x01. Each sensor should be assigned a unique address when multiple devices share one RS485 network.

Q6. Why is there a vent tube inside the cable?

A6. The vent tube provides atmospheric-pressure compensation for the gauge-pressure sensing element. It must remain open and protected from water ingress.

Q7. Can the transmitter measure oil?

A7. It can be used with water, oil and other liquids that are non-corrosive to stainless steel. For continuous measurement, the source specification limits medium temperature to 60°C or below.

Q8. Can it be installed horizontally?

A8. Yes. Vertical, inclined and horizontal installation are supported, provided that the sensing end is exposed to the liquid and is not blocked or buried by sediment.

Q9. Can RS485 communication reach 2000 meters?

A9. The transmitter specification states communication distances up to 2000 m. Actual performance depends on cable type, topology, interference, baud rate, termination, power supply and field conditions.

Q10. Can the data be sent to a cloud or private server?

A10. Yes. The RS485 Modbus transmitter can connect to a compatible RTU, data logger or IoT gateway, which can then transmit the measurement data through 4G, Ethernet, Wi-Fi, LoRaWAN or other supported communication systems.

NBL-L-WLPS for Water Level and Liquid Level Monitoring

The NBL-L-WLPS Submersible Water Level Transmitter combines a diffused silicon pressure sensor, IP68 submerged construction, vented atmospheric-reference cable and RS485 Modbus communication for continuous water and liquid-level monitoring.

When selecting the transmitter, specify the required measuring range, measured medium, cable length, accuracy class, installation conditions and communication requirements so the sensor can be configured for the application.