Hydrostatic Level Sensors

Hydrostatic pressure sensing devices for measuring liquid level and converting it to an electrical signal to send to other instrumentation.

Hydrostatic level sensors for measuring the pressure generated by a static head of liquid. Use hydrostatic level sensors to measure fluid level in storage tanks, processing vessels, header tanks, pump inlet head and other applications where hydrostatic pressure is used to determine liquid height.

• LMP307 Submersible Level Transmitter - Submersible level transmitter for measuring liquid level with a 4-20mA current loop or a 0-10V voltage output plus optional ATEX approval for intrinsically safe use in hazardous areas in ranges from 1mH2O up to 250mH2O. The LMP307 is suitable for use on potable water with no leaching, and can be supplied with a drinking water certificate according to DVGW and KTW.
• LMK458 Marine Approved Hydrostatic Level Transmitter - Marine approved level transmitter with 4-20mA output for measuring level of contents inside ship ballast, fuel, liquid cargo or wastewater tanks
• LMK382 Low Range IP68 Waste Water Level Transmitter - Submersible Low Range waste water level transmitter with intrinsically safe option for monitoring the level of sewage and effluent in water treatment plants.
• LMP305 Borehole Level Transmitter - Submersible stainless steel pressure transmitter ideal for geotechnical surveying with a 19mm diameter for measuring hydrostatic water level in bore-holes.
• 18.605 G Low Cost Submersible Diesel Fuel and Water Tank Level Sensor - Low cost OEM diesel fuel or water level sensor for installing inside or outside a storage tank. 
• LMK387 Cleanable Sewage and Sludge Pressure/Level Sensor - Rugged and easily cleanable pressure/level sensor for use with waste water sewage or sludge.

• Cement plant process water basin level sensor
• Stilling well 3ft range SDI-12 interface lake water level sensor
• 12ft high ink tank screw-in 4-20mA output level sensor
• Remote water tank level monitoring via GSM mobile network
• Fleet management system submersible 3000mm height petrol tank level ATEX rated pressure sensor
• Industrial dishwasher 0-1m 0-10Vdc water level sensor
• Floating dry dock ballast tank 14ft range 4-20mA output submersible seawater level sensor
• Automatic fire pump engine 48 inch range 0-10Vdc output diesel tank level sensor
• -5…+50degC temperature and 10m range level dual 4-20mA submersible borehole transmitter
• Dairy farm 6m high milk storage vat 4-20mA level transmitter
• Brewing tank 2000mm range 0-5Vdc output stainless steel 316L beer level sensor
• Irrigation water channel and storage dam 10m range SDI-12 submersible level sensor

Description

Hydrostatic level sensors are pressure sensing devices specifically designed for use on liquid level measurement applications.

All liquids which are under the influence of gravity generate a hydrostatic pressure. This pressure is similar to the weight of a solid object, but because of the fluid state it is possible to measure how the weight of the liquid varies with height.

The resulting pressure at different heights is directly proportional to the weight of a liquid between the surface and a specific height point. The weight of the liquid can be derived from the mass and force (gravity). The mass can be derived from the density and volume of the liquid. The volume of a liquid can be derived from the dimensions of the vessel containing the liquid. If the vessel has a fixed length and width, then the height is directly proportional to the volume, mass, weight and therefore the pressure.

A hydrostatic level sensor is an instrument for measuring the height of a liquid and converting it to an electrical signal. The hydrostatic level signal output can then be utilised by other instrumentation to display, monitor, log or control the liquid level.

There are many different types of technology used to measure liquid level, there are sensors that can be mounted above the liquid such as ultrasonic or radar which bounce a sound or electromagnetic wave off the surface of the liquid and use the travel time to determine the distance from the liquid surface.

For liquid filled tanks a pressure sensor can be installed in a hole at the bottom of the tank which measures the hydrostatic pressure generated by gravity acting on the liquid.

Another method is to lower a hydrostatic level sensing probe into the tank and immerse it in the liquid to measure the pressure generated by gravity acting on the surrounding liquid.

Advantages

1. Easily fitted at ground level to any port or take off, which is also convenient for maintenance
2. No protrusion inside vessel
3. Not affected by any surface disturbances such as turbulence, foaming, vibration
4. Small compact size possible
5. Compatible for conductive or non-conductive fluids
6. Flush diaphragm types prevent clogging and works with thick liquids and slurries containing solids

Disadvantages

1. Pressurised or vacuum sealed vessels require a more complex installation
2. SG or density change affects calibration
3. Flush diaphragm types vulnerable to mechanical damage from debris, cleaning processes
4. Requires regular calibration due to gradual error shifts
5. Installed in a position below the lowest required liquid level
6. Fittings must be leak tight
7. Diaphragm movement vulnerable to clogging, wear and tear
8. High cost