pool ph/orp sensors
- Thread starter pittom
- Start date
CAI_Support
Senior Member
Ph pool sensor normally output 59mV/PH change, and its input impedance is 400MOhm.
If you could get an op-amp meeting those requirement, you could make the op-amp output in WebControl analog input range, then measurement is possible. Ross' IO board allows adding an op-amp, but its impedance is not high enough, you may have to pick a different op-amp has 400MOhm input impedance to replace Ross' stock op-amp.
If you could get an op-amp meeting those requirement, you could make the op-amp output in WebControl analog input range, then measurement is possible. Ross' IO board allows adding an op-amp, but its impedance is not high enough, you may have to pick a different op-amp has 400MOhm input impedance to replace Ross' stock op-amp.
CAI_Support
Senior Member
Chip like TI OPA656 has input impedance 10^12 Ohm, probably could do the trick. Most Ph or ORP sensor measurement also need to calculated with temperature influence considered. That could be done in PLC logic.
I was thinking of something like this
http://www.practicalmaker.com/products/arduino-shields/bnc-sensor-shield-assembled
http://www.youtube.com/watch?v=YGYd8z5uD4M
the water temp is 98F stand by 103F going in temp. Looking for ph reading 7 to 8
http://www.practicalmaker.com/products/arduino-shields/bnc-sensor-shield-assembled
http://www.youtube.com/watch?v=YGYd8z5uD4M
the water temp is 98F stand by 103F going in temp. Looking for ph reading 7 to 8
CAI_Support
Senior Member
That is just an op-amp, I am sure Ross' board can do it, too. I can not tell what its input impedance by looking the pictures.
CAI_Support said:
OK, after all the discussion I decided not to be lazy and just work it out.
The typical input current for the amp I am using, in the non-inverting configuration should be around 200 megohms.
In the worst-case input current, it should be around 25 megohms.
25 megohms is probably not really good enough for a precision pH sensor unless its output is buffered.
200 megohms is probably adequate.
So my board would likely work adequately.
Upside is that with
59mV/pH should give a total input swing of 0.826V from 0pH to 14pH
To interface with the WC8 analog input, this is a gain of just over 10dB which it will achieve *EASILY*.
(I'm using my amplifiers with shunts that produce only 50mV full scale)
CAI_Support
Senior Member
Thanks, Ross. If anyone has interest in that IO/amp board, please send private message directly to RossW.
It will be interesting to see how that pool ph and orp monitoring work out. Ph sensor does need to periodically calibrate against known solution. I think user can write PLC program to convert the voltage to PH value. In that PLC program, considering the temperature compensation to the PH value.
It will be interesting to see how that pool ph and orp monitoring work out. Ph sensor does need to periodically calibrate against known solution. I think user can write PLC program to convert the voltage to PH value. In that PLC program, considering the temperature compensation to the PH value.
pittom said:
Have built a board, tested and recalibrated for 0-1V inputs. Will be posting it to Tom shortly.
Also, for the interest of anyone else around, I also made a bunch of stand-alone 4-channel amplifiers. These use exactly the same chip and circuit, except that it has 4 channels instead of 3, and has screw terminals for output as well as input. (Excuse the crap soldering on the prototype, I couldn't find my glasses, it was soldered by feel (and not well! They're all done with hot air nowdays and are much neater than this!)
I'm very new to all this and I don't know my rump from a hole in the ground when it comes to most of what I been reading on this forum, with all that said I came accros this pH sensor, how would this fit into a WC setup:
http://www.vernier.com/products/sensors/ph-sensors/
I'm looking at going beyond controlling my wood boiler to controlling a complete Aquaponics setup, and pH is critical to monitor in Aquaponics.
http://www.vernier.com/products/sensors/ph-sensors/
I'm looking at going beyond controlling my wood boiler to controlling a complete Aquaponics setup, and pH is critical to monitor in Aquaponics.
Hi Chris,
I am going to start a new topic (or someone can)What did you make with wc8 or wc32. Right now i have 5-wc8 and a 1-wc32 controlling
1-hot tub (it is outside in pa very cold)keeps pipes from freezing,ph/orp sensor soon
2-pool with heater in summer time ph/orp sensor soon
2-home alarm system/automation
3-turtle and snake tank heat and lighting
4-2 zone home heating/cooling
5-rv/truck use it all year hunting/fishing,controlls heat lights and pipe/water temp from freezing.Cant wait till it is sim card ready
All of this is controlled from my cell phone(note 2) or pc.I wrote my own web page with all boards on it ( http://www.virtualmechanics.com/products/spinnerpro/ )
I am going to start a new topic (or someone can)What did you make with wc8 or wc32. Right now i have 5-wc8 and a 1-wc32 controlling
1-hot tub (it is outside in pa very cold)keeps pipes from freezing,ph/orp sensor soon
2-pool with heater in summer time ph/orp sensor soon
2-home alarm system/automation
3-turtle and snake tank heat and lighting
4-2 zone home heating/cooling
5-rv/truck use it all year hunting/fishing,controlls heat lights and pipe/water temp from freezing.Cant wait till it is sim card ready
All of this is controlled from my cell phone(note 2) or pc.I wrote my own web page with all boards on it ( http://www.virtualmechanics.com/products/spinnerpro/ )
