ATLPipeEngineer
Civil/Environmental
Can you do that with a pressure transducer or is the depth too low?
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What is best method to measure level in 15-foot deep clear well?
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There are submersible pressure transmitters that measure the hydrostatic head pressure - very accurate, easy to install. They come in different ranges, you'd need a one on the lower range for only 15' water.
Here's one that is 0-15 feet range:
Link
The transmitter hangs off the end of a cable that has two electricsl signel/power wires and small plastic tube that provides a vent to atmosphere for the reference side of the pressure transmitter. It is advisable to terminate the vent tube in a desiccant package to limit the amount of humidity that gets into the tube, because moisture will condense in the coolest part when the cool part below dewpoint temperature and if water collects in the vent tube, then the transmitter will show an erroneous lower than expected level because the condensed water appears to be a high reference pressure and pressure transmitter work by subtracting the reference side from the measured side.
4-20ma signal are reliable with a commercial 24Vd power supply. Lots of devices to read-out the signal - you probably know what you need on that end.
Bubblers use a regular pressure transmitter but require a constant flow pneumatic regulator and a constant supply of compressed air. 100 year old technology and still used today, though.
There are ultrasonic and radar, non-contact transmitters. Now about 6th and 5th generations, much better than the 1980's versions. Neither can distinguish between water level and foam, but I doubt you're going to have foam in a clear well. Both can have difficulty dealing with water on their transmitter face (ultrasonic) or antenna (radar). They too are industry standard 2 -wire, 4-20mA devices.
Here's one that is 0-15 feet range:
Link
The transmitter hangs off the end of a cable that has two electricsl signel/power wires and small plastic tube that provides a vent to atmosphere for the reference side of the pressure transmitter. It is advisable to terminate the vent tube in a desiccant package to limit the amount of humidity that gets into the tube, because moisture will condense in the coolest part when the cool part below dewpoint temperature and if water collects in the vent tube, then the transmitter will show an erroneous lower than expected level because the condensed water appears to be a high reference pressure and pressure transmitter work by subtracting the reference side from the measured side.
4-20ma signal are reliable with a commercial 24Vd power supply. Lots of devices to read-out the signal - you probably know what you need on that end.
Bubblers use a regular pressure transmitter but require a constant flow pneumatic regulator and a constant supply of compressed air. 100 year old technology and still used today, though.
There are ultrasonic and radar, non-contact transmitters. Now about 6th and 5th generations, much better than the 1980's versions. Neither can distinguish between water level and foam, but I doubt you're going to have foam in a clear well. Both can have difficulty dealing with water on their transmitter face (ultrasonic) or antenna (radar). They too are industry standard 2 -wire, 4-20mA devices.
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Sight glass? (I kid).
A stick with a float or a float to a string pot/string encoder?
Is it the water column depth that is important or the water level? If there is a reference point that is in the upper level of the water then any pressure below that point is computable. Lots of options depending on the precise function that is to be performed based on the information.
A stick with a float or a float to a string pot/string encoder?
Is it the water column depth that is important or the water level? If there is a reference point that is in the upper level of the water then any pressure below that point is computable. Lots of options depending on the precise function that is to be performed based on the information.
15 ft only? I've got a 25-ft tape measure you could borrow
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
A lot of ultrasonic proximity sensors have parallel distance outputs too that are right in that distance realm. I'd prefer those since nothing is in the water then.
Keith Cress
kcress -
Keith Cress
kcress -
If there is no access to the side of the clear well, I would recommend a submersible Level Transmitter. If you have access on the side, use a differential pressure transmitter. If there is velocity in the tank, use a stilling well.
Options
Stilling well
DP Transmitter
Options
Stilling well
DP Transmitter
There is a long list of technologies you can use. If you want non-contact then I prefer ultrasonic or radar. I have seen but never used the submersible transmitters. I assume they output absolute pressure as there is no differential input. For a clearwell it seems a good option. There are also many types of immersion type probes but I think newer technologies have made them largely obsolete as they have the disadvantage of being the length of the entire sensing range.
Brad Waybright
The more you know, the more you know you don't know.
Brad Waybright
The more you know, the more you know you don't know.
>submersible transmitters. I assume they output absolute pressure as there is no differential input.
No, submersibles definitely measure gauge pressure. They all have a flexible atmospheric reference tube that runs the entire length of the wire cable.
No, submersibles definitely measure gauge pressure. They all have a flexible atmospheric reference tube that runs the entire length of the wire cable.
Submersible level transmitters measure the hydrostatic pressure from the bottom of the wet well, not on the cable and typically have a 4-20 ma output.
Ultrasonic or radar. Disadvantages: Ultrasonic level sensors are typically a more expensive option and require more care in their installation to ensure there are no obstructions (i.e. pipes, cables, walls, rails, etc.) within the cone angle that would impede the sound wave travel. In many lift stations there just isn’t a good place to mount the sensor and avoid these obstructions. Next, there is more time involved in the initial setup as their outputs typically need calibrated for every station based on where the sensor is mounted. Foam and condensation are also issues for this technology; as foam will produce false level readings and condensation on the sensor head, can eliminate the signal altogether. Lastly, most of these sensors are not designed to be submerged so flooded stations would ruin the sensors.
Ultrasonic or radar. Disadvantages: Ultrasonic level sensors are typically a more expensive option and require more care in their installation to ensure there are no obstructions (i.e. pipes, cables, walls, rails, etc.) within the cone angle that would impede the sound wave travel. In many lift stations there just isn’t a good place to mount the sensor and avoid these obstructions. Next, there is more time involved in the initial setup as their outputs typically need calibrated for every station based on where the sensor is mounted. Foam and condensation are also issues for this technology; as foam will produce false level readings and condensation on the sensor head, can eliminate the signal altogether. Lastly, most of these sensors are not designed to be submerged so flooded stations would ruin the sensors.
Near and dear to my heart, there are laser level meters:
Accuracy is only ±4 cm, but its beam footprint is only about 30 cm at 100 m
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
Accuracy is only ±4 cm, but its beam footprint is only about 30 cm at 100 m
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
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