Hydrostatic Liquid Level Sensors

Collection of resources for selecting and using a hydrostatic liquid level sensor.

Use this page to navigate between products used for measuring depth and level, application articles about liquid level measurement, questions answered on measuring hydrostatic pressure, technical jargon about hydrostatic level measurement and some useful technical reference documentation.

Hydrostatic liquid level sensors are pressure sensors which are specifically configured to measure the vertical height of a given fluid above the installation point of the sensor. The measured hydrostatic pressure is directly proportional to liquid height and the conversion ratio is dependent on liquid density and local gravitational force.

Choose a hydrostatic liquid level sensor from the list below to view product specification details and request a price quotation.

Contents

Product Types

Hydrostatic Level Sensors - Hydrostatic pressure sensing devices for measuring liquid level and converting it to an electrical signal to send to other instrumentation.
Chemical Resistant Hydrostatic Liquid Level & Pressure Sensors - Pressure transmitters & transducers that are resistant to chemical corrosion for measuring the hydrostatic level of storage tanks or process pressures.
4-20mA Output Hydrostatic Level Transmitters & Sensors - Liquid level transmitters with a 4 to 20 milliamp current loop output signal for determining liquid depth or the fluid level by measuring the hydrostatic pressure.
Combined Temperature and Hydrostatic Liquid Level Sensors - Combined temperature & level sensors which provide a signal output for both temperature and hydrostatic pressure measurement from one device.
SDI-12 Hydrostatic Liquid Level Sensors - SDI-12 interface hydrostatic level sensors with a serial digital interface for measuring liquid depth and returning the reading to low powered telemetry instrumentation in remote locations.
Submersible Hydrostatic Level Sensors & Probes - Level sensors for submerging permanently in liquid to determine the level or depth of fluid by measuring the hydrostatic pressure.
Small Diameter Borehole Hydrostatic Liquid Level Sensors - Hydrostatic level sensors for measuring ground water level in small diameter bore-holes.
Seawater Hydrostatic Liquid Level Sensors - Hydrostatic level sensors which are suitable for immersing in seawater for long periods to monitor depth and tidal changes.
Absolute Unvented Reference Hydrostatic Liquid Level Sensors - Non-vented absolute range hydrostatic level sensors for measuring liquid level where it is not possible or practical to connect a vented gauge reference.
Marine Approved Hydrostatic Liquid Level Sensors - Marine approved hydrostatic liquid level sensors for use in marine environments.
Freshwater Hydrostatic Liquid Level Sensors - Liquid level sensors for measuring the level of freshwater in tanks, boreholes, reservoirs, rivers, canals, streams and wells.
Plastic Submersible Hydrostatic Liquid Level Sensors - Chemical resistant submersible level sensors with a PVC housing and ceramic diaphragm for measuring the hydrostatic level of harsh chemicals.
Plastic Externally Fitted Hydrostatic Liquid Level Sensors - Plastic liquid level sensors with a PVDF housing and Ceramic diaphragm for fitting to the outside of a chemical storage tank.
Brackish Water Hydrostatic Liquid Level Sensors - Brackish water depth and level sensors with housing material for use with tidal and coastal sea water.
Hazardous Area Externally Fitted Hydrostatic Liquid Level Sensors - Hazardous area external mount level sensors for use in zones where there is a high risk of explosive gases being present.
Hazardous Area Submersible Hydrostatic Liquid Level Sensors - ATEX/IECEx intrinsically safe IP68 sensors for liquid level measurement in intrinsically safe installations on petrochemical, pharmaceutical, landfill and sewage treatment sites.
0-10 Volts Output Hydrostatic Sensors, Probes & Transducers - Analog output hydrostatic sensors with a 0 to 10 volt amplified output signal for measuring liquid head pressure or fluid level.
Water Resistant Pressure Sensors with Strain Gauge Output - Water resistant strain gauge output pressure sensor for measuring hydrostatic liquid level or underwater system pressures.

Select a hydrostatic liquid level sensor for your application

Find product information for the type of hydrostatic liquid level sensor you are looking for. Liquid level sensors and probes for measuring and controlling hydrostatic fluid level in liquid storage tanks, boreholes, reservoirs, rivers, waterways, tidal water or sea water. Find liquid level instrumentation compatible with a range of media types such as water, saltwater, wastewater, diesel, petroleum, chemicals and caustics.

If you would like us to select a hydrostatic liquid level sensor for you, then please use this form to specify your requirements.

Product Help

High pH basic/alkaline

I am looking for a sensor to measure the change of level in a reactor which works at atmospheric pressure. The liquid in the reactor has a very basic pH (12-14), what type of level sensor could be used?

Typically we would suggest pressure sensors with a plastic housing, FFKM seals, and a ceramic diaphragm for acid/alkaline applications. However each chemical has unique properties, which also vary with different concentrations and temperature, so we recommend users assess suitability by comparing each material used in the construction of the sensor to the chemical being measured.

If you use a hydrostatic pressure sensor that is referenced to atmospheric pressure via a vent path behind the sensing diaphragm, then you do not need to compensate for atmospheric pressure in the reactor, since each will cancel the other out.

Altitude effect on hydrostatic reading

Does a hydrostatic level sensor give the same output signal if the tank is at sea level or say on a mountain 2000 metres high, since the air pressure acting on the liquid surface is lower on top of the mountain?

If the hydrostatic level sensor is vented to atmosphere on the reference side of the pressure sensing diaphragm, it will self compensate and be unaffected by changes in altitude.

Measuring water level using a pressure sensor is mainly affected by changes in density and gravity. A 2000 metres change in height will change the pressure by about 0.3 mmH2O due to changes in gravity, so only a very small amount.

Chlorine dioxide solution tank level

Do you have a sensor that can measure a corrosive liquid with a reasonable accuracy in small tank application? The liquid that will be measured is a generated chlorine dioxide solution, so PVDF and Teflon are usually the contacted material of choice. I think PVC would also be acceptable. The tanks are typically 49″ tall. The sensor can be mounted on the bottom of the tank or on the side at the bottom.

We would suggest either the LMK351 for screwing into the side of the tank at the bottom or the LMK809 for lowering to the bottom of the inside of the tank. Both sensors can have PVDF housings with a Ceramic diaphragm for chemical resistance, plus a choice of seal materials.

Groundwater level transmitter for 5/8 inch diameter tubing

I’m interested in your small diameter groundwater level transmitters, however I need something less than 12mm in diameter to fit inside a 5/8-inch ID tube. Do you have anything this small?

We would suggest the MTM3000 which is a submersible miniature pressure transducer with a diameter of 10 mm.

Vented or non-vented pressure transducer for measuring liquid level

We have a requirement to measure 0-10 meter column of water. In the past we have used a transducer with a 1 bar range and a 4-20 mA output. The accuracy needed is around +/- 5cms. We do not understand the advantage and difference between vented and non vented transducer, can you guide with this and suggest a suitable type of transducer to measure the water level?

10 mH20 is approximately the same as 1 bar, see our meters of water column page for a more precise conversion. A 5cm accuracy is equivalent to a 0.5% full scale accuracy for a 10mH2O range instrument.

Where possible you should always use a vented device, since it is a more accurate and a simpler method compared to using a non-vented pressure measurement device for measuring liquid level. The vast majority of installations use a vented pressure sensor to measure liquid level.

Reducing lightning damage to submersible water level probes

We have a problem with the control of a borehole pump. The borehole pump is at the base of the well at around 250 feet deep. The level control system has been wiped out by lightning on more than one occasion. The electrical circuit is fitted with surge protection and lightning arresting components, so I was wondering if the submersible level probes might have something to do with the problem?

If the screen wire which runs through the level probes signal cable is connected at the sensor end to a metal body and also connected to a grounding earth at the surface, this can increase the chance of damage from voltage surges induced by lightning strikes. If the screen is connected at both ends it is possible for an earth loop to be established. Since the level probe is submerged in water, an earth loop is created from the surface ground, down the length of the sensor cable, out through the sensor into the water, and eventually back to the surface ground.

If the level control system is subjected to a voltage surge due to a lightning strike in the vicinity, some of the high voltage energy which is diverted to ground by the lightning arrestors will flow around the earth loop and take a longer amount of time to dissipate. This lingering voltage surge can cause interference and permanent damage to sensitive circuitry such as sensor components and micro-electronics.

Since the purpose of the earthed screen wire is to protect the long signal cable (which effectively acts like an antenna picking up electromagnetic interference) from EMI, it only needs to be connected to an earthed ground at one end to provide protection from the normal levels of interference such as radio waves, electric motors and pumps. Check to see if the sensor screen is connected to ground at both ends, and if it is, try disconnecting it at the sensor end to see if that reduces the occurrence of failures due to lightning strikes.

It is very difficult to eliminate damage caused by lightning entirely since the energy involved is so great, but an optimised installation can greatly reduce the likelihood of damage and lower the recurring cost of replacement instrumentation in a lightning prone location.

How to use SG and tank height to specify pressure range

I need to measure the level of liquid by using pressure transmitter fitted at the bottom of the tank. Please suggest the formula to use to calculate the range for pressure transmitter?

The tank details are:

Height of tank is 3750 mm
dia of the tank is 2500 mm.
The specific gravity of the liquid is 1.3089

The formula for converting liquid level to pressure is:

Pressure = Liquid Height x Liquid Density x Local Gravity

Liquid Density = Water Density x Specific Gravity

Assuming the local gravity is 9.80665 m/s², the pressure range in this case would be:

Pressure Range = 3.75 x (1000 x 1.3089) x 9.80665

= 48,134.7157 Pa
= 0.48134.7157 bar
= 6.98135027 psi

Is volume ∝ hydrostatic pressure in any shape tank

If you use a submersible pressure sensor to measure the level of liquid in a square tank, will it give an accurate indication of the remaining volume, even if the tank is tipped up on one edge? Is the shape of the tank important, or do you only need to know the total volume and the height of the tank to get an accurate indication of remaining volume?

A submersible pressure sensor will provide a signal that is linearly proportional to liquid height and is independent of length & width of the tank.

If the sides of the tank are vertically uniform (horizontal cross sectional area does not change), the output signal will be linearly proportional to the volume left in the tank.

However if the sides are not uniform vertically, as is the case in your example with a tilted square tank, the output will not be linearly proportional to the volume left in the tank.

Wine Tank Levels

I am looking for a food grade pressure sensor to monitor wine tank levels. The tanks are either stainless steel or cement, and they range from 50.000 to 200.000 litres. Please advice if you have a suitable sensor with a 4-20mA output?

We would suggest the DMP331P which is a hygienic level sensor suitable for use with food & drink, as long as the food grade oil filled diaphragm seal option is specified. The components that will be in contact with the wine are all stainless steel 316L.