Hello all,
I've recently set out on a project that needs to read air pressure in a pipe/tube. It should not ever have to read more than 300psi, usually it'll be reading around 80psi. It then needs to transmit the pressure readout to another arduino a mile or less away.
What I still cannot find is a digital air pressure gauge or meter that screws into a pipe or tube socket and reads the pressure and gives a readout with a +-0.5psi accuracy to the Arduino. Can anyone point me to a product or company that offers this? I prefer that it's IP rated 55 or better and costs less than $500. It must not operate on more than 5v. Thanks!
Bump.
Again, all I need is a digital pressure guage compatible with Arduino that can read around at least 125 psi. Preferably water and dust resistant, but it's not necessary.
Thanks and regards,
Chris
Your spec looks a little too industrial for the average hobbyist, so I'd suggest contacting a firm like this http://www.hydrotechnik.co.uk/ to find a gauge with digital output, then come back to the forum for help with implementation.
I have no connection with the company in the link. I just picked the first local company that Gurgle found, that's where I'd start.
@Martin-X thanks for the link!
http://www.hydrotechnik.co.uk/product/es-10-mini-stainless-steel-pressure-transducer-0-to-20-bar-range-m8x1-male-thread-connection
seems like a good option to me at the lowest pressure range. I don't know how to read the pressure from it with an Arduino, though. And I don't think any of their guages or meters with a screen or dial have an output, but prove me wrong.
So, basically, how do I read the pressure value from the product linked to above?
Thanks and regards,
Chris
Note: I know I've done a lot of also/edit/note posts, this is because for some reason the laptop I'm using doesn't like to let me edit anything except the main post, so sorry about that. I'll have it looked into when I get home.
In my previous post, after further research:
- Link #1 has no way to be read by an Arduino, it's purely screen based readout.
- Link #2 was broken but is my best bet. Updated link below.
- Link #3 is a pressure switch, not a gauge or meter, so it only modifies a circuit past a certain pressure, whereas I need Arduino to read the value of the pressure.
This (click) is my best bet at a pressure meter/gauge that can give send a pressure reading to an Arduino, but it is a transducer, so it sends the pressure by voltage based on how high the pressure reading is, but I don't know how accurate this is and how accurate of a voltmeter I can find to interpret it. Plus it uses too many volts to supply with Arduino and I don't think it's designed to be screwed in to a pipe, but prove me wrong.
www.wika.us seems to carry gauges that look to be like I need, but I have to go so I'll post again if I find what I need there. If anyone can point me to a particular company or model, I'd appreciate it.
Thanks and regards,
Chris
Newest update: It seems all of Wika's products use Electrical output meaning you have to interpret the voltage it puts out as a certain PSI reading which is not preffered and I don't know how accurate it is. So for anyone just now reading this article:
I am trying to find an inline or "screw in" (don't know the term) air pressure meter/gauge/dial that outputs the pressure in a signal that Arduino can understand.
I would much prefer if it was a digital signal because it's my understanding that analog can be less accurate and it takes a little more code (I think?), but if it's an accurate voltage signal than that's OK. If it has an IP Rating of 54 it's even better, but some products have no IP rating and that's fine too. If it can run on 5v or less that's great, but anything is fine, and it's rare but if it's self powered that's amazing. This entire paragraph is just preferences.
Thanks and regards,
Chris
The Wika gauges look the most promising. To improve your chances of finding more like that, try the term "Ratiometric" in your searches. The best resolution you can achieve with voltage output will be Max PSI / 1024, so for a 300PSI gauge you'll get measurements with a 0.3 PSI resolution (resolution shouldn't be confused with accuracy, by the way).
@Martin-X Correct me if I'm wrong, but resolution is how accurate the voltage is in proportion to pressure, accuracy is how accurate the gauge is able to read the pressure, yes? Sorry if I sound like a bit of a noob here. And I am also correct in assuming that ratiometric just means that the output voltage rises proportionally with the pressure? So if the sensor can read 0-200 PSI and output 0-10 volts, for example, 0psi=0v, 200psi=10v, 50psi=2.5v, 100psi=5v, and so on?
I'll continue looking for these and look back at Wika's supply.
Thanks!
Chris
Turns out this is the best option from Wika: http://www.wika.us/pgt21_en_us.WIKA?ProductGroup=60605&21=1018
Depending on how high the output voltage can go, I need to put resistor(s) on wire coming back to analog and account for the change. Basically the analog slot will work as my voltmeter and the arduino will do the math to figure out the pressure based on the return voltage. Thanks for the help @Martin-X, if anyone wants to add anything that's fine, but this is pretty much solved. Thanks!
Chris
Build_and_Break:
resolution is how accurate the voltage is in proportion to pressure
Not quite, resolution is the smallest change in pressure that can be determined by an Arduino. There's a good discussion on the Arduino ADC here analogRead - divide by 1023 or 1024? - Programming Questions - Arduino Forum which may be of interest.
Build_and_Break:
accuracy is how accurate the gauge is able to read the pressure, yes?
Yes.
Build_and_Break:
ratiometric just means that the output voltage rises proportionally with the pressure?
Yes, it's a fancy word for linear output.
Best of luck with your project.
ratiometric just means that the output voltage rises proportionally with the pressure?
"Ratiometric" means that the gauge output voltage at a given pressure is proportional to the gauge input voltage (i.e. the power supply). Usually, it applies to gauges that use a Wheatstone bridge sensing element arrangement.
The PGT21 gauge you linked is not ratiometric, but you can select from several output voltage and input voltage ranges.
Thanks! @Martin-X and @jremington !
@jremington Not that I don't believe you, but how can you tell that it is not ratiometric? I see no mention of it anywhere on its product page or datasheet, which is odd. I also can't seem to find any sensors on Google that are labeled or described as ratiometric, linear, or strain gauge, besides from some questionable and unofficial retailers with little product info. 
Any help is appreciated.
Thanks, Chris
@jremington After reading your latest reply a few time I'm a little confused still, I'll admit.
Suppose I have a sensor which takes 10 volts and outputs 0 to 10 volts. It has a range of 0 to 200 PSI. Suppose it reads 120 and outputs 6 volts. Suppose it read 90 PSI and it outputs 4.5 volts.
Does this make it ratiometric?
Or do you mean to be ratiometric the sensor must also accept any voltage and still return a voltage proportional to the pressure?
Even though the Wika sensor I linked to isn't ratiometric like you said, will it still output a voltage proportional to the pressure reading like the example sensor I described above?
Thanks, Chris
If the gauge were ratiometric, it would say so on the data sheet. Instead, the gauge you linked has a calibrated output, with voltage (or current) proportional to pressure, selected from several possible ranges.
Google "ratiometric pressure gauge" for a more detailed explanation, but here is one: What is Ratiometric Output? | From UK Sensor Experts
Thanks for the clarification, @jremington
This thread is once again solved, but I'll leave it open for up to 7 days to allow for additional comments.
Thanks and regards,
Chris