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Tank Level Application with Ultrasonic Sensor


A company that produces various liquids had a need for an indicator that could display, in liters, the amount of solvent in a tank. Because the solvent is corrosive, an ultrasonic level sensor was used. This type of sensor uses ultrasonic signals, bounced off of the top of the liquid, to determine distance, or depth. The customer calibrated this sensor to produce 4 mA of current when the tank was empty, and 20 mA of current when the tank was full. This signal was to be measured by a 4-20 mA meter, calibrated to read in gallons. Any one of our 4-20 mA meters would have worked for this application, if the tank had parallel sides, but this tank was round, horizontal to the ground. This meant that while the signal measured was linear to depth, it was not linear to liters of liquid in the tank. (There is more volume per cm of depth in the middle of the tank, compared to very little volume per cm of depth near the top and bottom.) Because this signal is non- linear, an PXP panel meter was best suited to fit this customer's needs. Instead of selecting a reading of 0 at 4 mA, and 2000 at 20 mA, he was able to program 16 points along our input curve !

Water Detection in Diesel Storage Tanks

Model 38 Capacitance Level Transmitter Provides Cost Effective Oil Measurement with Water Detection Features

Oil or diesel tank level measurement applications often have a small water level below the hydrocarbon layer. This is typically a result of condensation or entrained water in the hydrocarbon liquid which eventually settles out. Most technologies accuracy is either affected by this lower water level or cannot operate correctly at all. The model 38 capacitance transmitter will allow the accurate measurement of the hydrocarbon level, as well as detect the water layer below. This feature will control your hydrocarbon level while continuously checking for water. How does it work? In a vertical capacitance probe installation, low dielectric constant (1.6-9) hydrocarbon levels such as crude oil, diesel, vegetable oil, etc. can be accurately measured. The level has a corresponding 4-20 mA output signal. When a high (+10) dielectric liquid such as water is detected by the probe, the mA output will indicate past the 20mA scale and over range at 20.6 mA. The 20.6 mA output indicates that the capacitance range of the transmitter has been exceeded and indicates that water or another high dielectric liquid is touching the probe.

This output can then be used by a PLC or any other control device to open a valve at the bottom of the tank to remove any water level touching the probe. Once the water level drops below the tip of the probe, the mA output will instantly lower and begin tracking the hydrocarbon level again. Controlled testing has revealed that measuring the hydrocarbon level and detecting the water below this level are both accurate and repeatable. In order to achieve these results, the transmitter must be configured and calibrated in the vessel with oil or another hydrocarbon only in contact with the probe. A bare probe must be used for all hydrocarbon based liquid applications and should be at the necessary length to detect the water level, usually 3”-4” from the bottom of the tank. With no moving parts and a reasonable price the model 38 solves two problems with one instrument and provides a cost effective level solution.


Low Cost Loop Powered, 4-20 mAdc Output
Integral Transmitter with Dual Compartment Housing
Solid State, Microprocessor Based - No Moving Parts
Complete Digital Calibration - Eliminates Analog Pots
External Magnet Calibration - No Need to Open Case
Partial Fill Tank Calibration - 2 Points With Only Partial Fill
Explosion Proof Enclosure, Intrinsically Safe Probes• Rugged Probe Designs
Eliminates Explosion Proof Conduit Seal Requirement
OptionsRemote Mounting up to 200 Ft. / 61 m
External Power Supply / Field Indicators
Variety of Probes Available• 316L SS Dual Compartment Housing

Hydrostatic Head

The 400 series of submersible pressure transmitters includes a number of completely submersible pressure-sensing transmitter models ranging from 0 to 1m water column to 0 to 500m, that contain an air vent tube for providing a pressure differential relationship between the hydrostatic head and the atmosphere. The transducer contains associated electronic circuitry for providing an analogue output, has an IP 68 protection rating, and requires a 24 Vdc ± 10% Power Supply
These transmitters can be used in applications such as:

Tank Level
Well Monitoring
Ground Water Monitoring
Down Hole
Surface Water Monitoring
Level Monitoring


Level monitoring & control of Water Reservoirs without contact, with or without remote display

Level Monitoring/Control of Wastewater, Fats, Oils, Grease (FOG), collection/inspection manholes & grease trap/interceptors, from overflow

Level measurement / control of wastewater collection manholes without contact. Compact Ultrasonic sensors with integrated digital indication, 1 or 2 contacts for maximum / minimum level or 0-10V / 4-20mA analog output.

Storm water manhole level measurement/control with ultrasonic sensor

Grease manhole level measurement/control with ultrasonic sensor

see ultrasonic sensors category