I've never seen an automotive pressure sensor that was absolute. They are all Gauge pressure. I very much doubt you have absolute transducers, most likely low accuracy gauge type
These are not what I would call high end transducers. This site claims 2% error without any explanation of how the error (if real) is calculated. Also you didn't mention how much off the 102 count your transducer.
Easy test. Connect the transducer to your arduino and leave it sit. Monitor the readings every couple of hours for maybe a day and see how stable it is. After that, repeat the test but warm or cool the transducer, see how much it changes with temperature. See if the short term change is stable enough for you to even consider.
For any pressure transducer the most unstable parameter is the zero offset. Even in the most costly sensors this is the most difficult characteristic to keep stable. And the arduino is not what I would call a precision device.
So I think you should look at your goals from the application side. A good rule of thumb is one should use a transducer at about 2/3 of the max range. This means you will require transducers with different ranges.
You mentioned your expected pressure values but you didn't mention what you need to measure to accomplish your goals. Is it there or not there? Or do you need values?
I realize you must stay with the Arduino for readings. However if you expect any precision I strongly suggest you get one with this chip on it MCP3421
The delta sigma conversion is the key here. They are inherently low noise and rejecting most periodic noise. You will need three of these, one for each transducer and one for the 5V transducer supply. I thought there was another type of delta sigma converter with multiple input channels but I couldn't find it in a quick eBay search.
Hi John Robert,
I was hoping you would chip in!
Thanks for the great ideas.
I have several transducers, 10, 30, 100&150psi max.
The two water tanks have a max water level of 2.2m which puts it in roughly in the range of the 10psi units.
The pool filter usually runs around 15psi, so I'll use the 30psi unit.
House line pressure is limited by regulator to 3bars, so the 100psi unit works there.
I characterized them all with a water column rig up to 3m over a couple of hours. Linearity was within acceptable range.
As mentioned before, my rain water temp is quite stable at 19°C, maybe dropping by a couple during a rainstorm...
Pool water varies between 25-30°C, depending on my solar thermal output...
I'm almost done with the firmware work and will see, if I can jury-rig a water column system for all 4 sensors at the same time. Since the software is logging every 15mins, this will make for some interesting data to share.
The plan would be power up the system, let it sit 10 mins, then record the 0m readings. Repeat in 24hrs, for 24hrs with 3m water column... This will sit in the workshop, so temperature swing will likely be about 10°C...
I'll report back.
Thanks again John Robert.
I'll keep your recommendation about MCP3421 in mind!