Hi (my first post and can I say many thanks to Kyle for setting this forum up - Im a bit of a newbie to electro chem or electro mech stuff and Ive found it hard to find info)
Ive designed a set up with one PH probe one ORP probe their EZO boards mounted on a T2 mounted on Arduino. It is designed to test swimming pool water and fire a dosing pump to add liquid chlorine when readings are within parameters. The calculation formula requires the PH to convert the ORP into Cl,ppm but Im falling over at the first step of getting the PH probe working
I desk tested and calibrated - all looked fine and realistic ( calib using test solutions, used pool water and compared to a chem test kit results)
the actual installation calls for the probes to be some 20 feet away from the Arduino
I bought properly insulated extension cables and these are routed well away from power supplies and pumps.
I know youve got to calibrate again after the extension
trouble is this did no make much sense - first the PH was reading 0 - issuing the Phext,1 command showed it was reading -2.45 - proceeded with calib mid point first - great it returns 7.00
changed solution to pH4.0 reading comes back 7.00 - wait a full 10 mins - now jumping 3.990 to 7.0
carried out calib moved on to cal,high,10 and using appropriate solution(Ph10.0). this time could not get it to return anywhere near 10.00 even after 20 mins.
the status reads ?STATUS,P,3.88
the slope reads ,?Slope 0.0,-2.00,518.81
Im not sure but that seems to tell me I’ve got a healthy 3.88 v at the probe despite the long cable
but the slope seems all over the place
I’ve tested the connections - they are good and tight bnc ones
I’m just not sure what else to test - all suggestions gratefully received - If anyone’s interested in a similar project I can post my arduino code (not pretty!) in the public domain in a separate post but right now I’ve just using a test rig where I can send individual commands to the EZO devices. Its nothing to do with my Arduino code
TIA and all the best