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Liquid Level Measurement
Measuring the amount of liquid present inside a storage vessel, pressure vessel or tank is a common requirement in the process control, effluent treatment and water treatment sectors.
Depending upon the type of liquid present in a vessel and any process conditions that are being undertaken there are a number of ways in which to measure the level inside tanks and vessels.
Ultrasonic Level Measurement
Ultrasonic Level Transmitters are an excellent way of measuring the liquid level in both open and closed vessels.
The ultrasonic level transmitters work by sending out an ultrasonic signal which reverberates from the liquid level and back to the transceiver. By using sophisticated electronics to compensate for environmental factors, including temperature, the changes in the height of the liquid from the transceiver can be accurately calculated.
By calibrating the ultrasonic level transmitter to the maximum height, minimum height and distance from the transceiver to the liquid level the liquid level can be easily calculated.
Our range of ultrasonic level transmitters use an isolated 4-20mA output which is directly compatible with our 4-20mA controllers to give a localised display. A 4-20mA signal can then be relayed to a PLC or digital chart recorder (or connected directly), which can precise volumes of liquid to be calculated.
Ultrasonic Level Transmitters aren't suitable for liquids that have low vapour pressures, that can foam or where there is turbulence on the surface of the liquid (such as liquids that are under agitation from an industrial mixer). Where this is the case, we offer hydrostatic level transmitters.
Hydrostatic Liquid Level Measurement
An alternative to ultrasonic level transmitters are our range of hydrostatic level transmitters.
These use the hydrostatic principle of calculating the pressure exerted by a head of liquid onto a precision sensor. Using the pressure information the height of the liquid present in a tank is calculated by the electronics in the sensor. This information is then transmitted to a compatible device such as our 4-20mA controllers, PLC or another compatible 4-20mA device.
One key component of using a hydrostatic liquid level sensor is to ensure that specify gravity of the measured solution is accounted for in connected instrument - which can be a 4-20mA controller such as the BC7635, a PLC or another device. This is normally pretty straightforward in the instrument calibration or setup and our technical team can talk you through any setup required.
Insertion Hydrostatic Level Sensor
An insertion hydrostatic level sensor has a front mounted BSP thread which is designed to be screwed into a threaded fitting or boss located at the bottom of a tank.
The insertion transmitters are manufactured in 316 stainless steel with a ceramic or stainless steel diaphragm - which means that the material to be measured should be compatible with 316 stainless steel.
The ranges or the insertion hydrostatic level transmitters is from 0 - 0.1 Bar through to 0 - 10 Bar with threaded connections from 1/4" BSP through to 1" BSP.
The outputs of the insertion hydrostatic level sensors are 4-20mA to for use with a compatible instrument.
Suspended Hydrostatic Level Sensors
As an alternative to a threaded insertion hydrostatic level sensor - we offer suspended level sensors which are perfect for suspending into open vessels, tanks or process vessels.
Rather than having an exposed diaphragm which reacts to changes in pressure - the suspended pressure transducers are supplied with a length of cable which is used to lower the hydrostatic level sensor into the tank. As the level of fluid increases on the hydrostatic level sensor the subsequent increase in pressure results in a change in the output 4-20mA signal which correlates to the level of liquid in the tank.
The suspended level transmitters are available in both 316 Stainless Steel and PVC with Ceramic sensor for increased chemical compatibility.
The suspended hydrostatic level sensors use a special vented cable which is designed to allow the suspended level transmitters to operate from ranges from as low as 0 - 0.5 metres of depth and as high as 0 - 200 metres depth.
4-20mA Controllers
As all of our level measurement transmitters use a 4-20mA signal to transmit the signal corresponding to the liquid level, we also offer a range of 4-20mA controllers.
These instruments supply power to loop powered devices, and then using the same two wires, receive the 4-20mA signal which is displayed on the front of the instrument. In addition to displaying the 4-20mA value scaled to corresponding measurement such as percentage depth, the 4-20mA controllers also offer 2 x relay set points, an alarm relay, and the ability to re-transmit a 4-20mA device to another instrument or PLC.
Liquid Level Measurement Range
Ultrasonic Level Sensors
Ultrasonic Level transmitters for measuring the liquid level in tanks and vessels where the liquid is non-foaming and without a low vapour pressure.
Manufactured in chemically resistant PVDF with loop powered 4-20mA output and 2" BSP threaded mounting.
The MF-C has a measuring range of 0.4 to 8 metres in length and features sophisticated temperature compensation for accurate level measurement.
Hydrostatic Level Sensors
The Hydrostatic Level Sensor range includes both our Suspended Hydrostatic Level Sensors for lowering into tanks using the attached cables, and our Insertion Hydrostatic Level Sensors which have a mounting thread which is designed to be screwed into the bottom of a tank to measure the liquid level inside.
All the hydrostatic level sensors output an industry standard 4-20mA signal for use with range of compatible devices.
The insertion hydrostatic level sensors offer ranges from as low as 0 - 0.5 Bar and as high as 0 - 10 Bar pressure.
The suspended hydrostatic level sensors offer ranges from as low as 0 - 0.5 Metres depth and as high as 0 - 200 Metres depth.
4-20mA Controllers
Our 4-20mA controller range includes panel mounting and surface mounting instruments designed to work with an industry standard 4-20mA signal.
Our controller range can supply power to a compatible 4-20mA loop powered device, and interpret the incoming change in current. This can then be displayed locally on the instrument LCD (liquid crystal display) and scaled as required to indicate percentages and absolute values where 4mA = X and 20mA = Y.
In addition to the local display our 4-20mA controllers include 2 individual set-points with corresponding relays which give high and low control, an alarm relay and the ability to output a second 4-20mA signal for integration to a PLC, digital chart recorder or an online data logging device.