I bought an air pressure sensor. Can that be wet ??
Can I connect a hose to the sensor y measure water pressure ?
The module sensor is one of this
XGZP6857 XGZP6857A
5V 0-40KPa
any help is welcome
the chip is rated only for clean, dry air or non-corrosive gases
the datasheet specifically states
"The only direct pressure medium you can use is dry air. The use of other media, in particular, corrosive gases (organic solvent based gases, sulfurous acid based gases, and hydrogen sulfide based gases, etc.) and media that contains moisture or foreign substances will cause malfunction and damage. Please do not use them"
Technically yes, if your sensor is above water and hose is filled with air, you can read water pressure. But it would violate "dry air" requirement on the description since the air in hose will become humid.
You need gas-barrier membrane hermetically sealed to inner surface of the hose. I see this pretty difficult as diy approach.
Maybe, exactly what do you plan on doing?
Air pressure sensors often have relative small ranges, while water pressure goes up much faster.
The range you mentioned 0..40 kPa is equivalent about 4 meter water depth (depending on salinity temperature (et al).
Thinking out loud:
I would place the sensor in a balloon filled with dry air. Glue the wires water tight, so no water leaks in. Then measure a new reference for air pressure above water. By putting the balloon under water the pressure will increase.
Latex is not good air barrier, maybe foil balloon could work..
If you measure through the side of the hose yes but be aware that flow in the hose will decrease pressure perpendicular to the flow (from the sides).
If stand a clear tube full of air sealed at the top into the side of the hose, change in water pressure will change the length of the air column which at the top has a nice dry air pressure sensor.
The more pressure that air column is under, the less that air will support water vapor.
I recall vacuum pumps had protective inline filters with a membrane.
At a guess, the membrane was PTFE. Made by Whatman. Millipore did selective syringe inline filters too.
I wonder if something like a rubber membrane would work, as in expansion vessels.
Another approach would be to dry the air with a desiccant. Molecular sieves, silica gel, plain or self-indicating. All easy to re-activate.
PTFE passes any gas and vapor, it's often used as waterproofing when gas permeability is desired.
If you describe your specific application, you can get better suggestions.
In case you want to use it as water level sensor of water storage tank, you can find better options. It would be quite difficult to make this sensor/hose combo to work in long term.
Expanded PTFE but not PTFE in general.
You are right.
Yes
It's used to separate water containing dissolved ammonia from pH electrodes.
The ammonia gas pssses through the PTFE membrane and alters the pH at the electrode.
By adding sodium hydroxide to water containing ammonia compounds, ammonia gas is produced.
It converts an ordinary pH elecode into an ammonia specific electrode.
Ordinary gas grade PTFE plumbing tape works really well
Gas grade sounds counterintuitive here, I would expect something that does not pass gas.
Maybe because it's heavily compressed in plumbing fittings?
In the US, the legal PTFE tape for use with gas fittings is the yellow stuff which is much thicker and denser than the common white tape.
My point was that "gas grade" tape is likely used to prevent gas passing. So using it for gas permeable membrane is counterintuitive. But maybe strong compression could make permeable membrane "non-porous sealant" ?
It does work.
I built dozens of ammonia continuous flow monitors.
When gas grade PTFE is used in plumbing and it's specified for gas (methane, natural gas) it's primarily purpose is to seal the threads on tapered fittings.
The leakage, if any, would have to pass through the convoluted thread pattern.
I used loads of the stuff in plumbing and gas systems.
The only gas that caused problems was hydrogen and we had to source high quality fittings like Swagelok.
As it's thicker than standard grade, it's much tougher but still allows the ammonia gas molecules to get through