I found that the Atlas circuits are quite good and can be used with a wide range of devices and get solid, stable readings. AFAIK they take a few readings then average them to reduce noise.
I had trouble getting readings within the 0.1 accuracies with the supplied circuit but with the same probe and an Atlas circuit I could easily get 0.01 stability.
I agree that the cheaper probes need calibrating more often.
I always worry that when my rez empties, the probe wonât hit water. Then the ph will flux n the auto dosed will go crazy.
I was just planning to drop the probe in the bottom of the rez and leave it. If that isnt possible because of a connector or something, then maybe a floating holder so it sits on top of the water at all times - like a chunk of foam maybe?
It never occurred to me that the shield circuit would/could be a source of error. Good info to know!!
Thatâs what I use as the Milwaukee instructions say to not fully submerse them.
Ya I need to suction cup it to the bottom
The Atlas one can be submerged, and all the cable, up to the BNC, for the life of the product.
If you do have your PH probe in your main tank, make sure there is a small circulating pump or similar pointing at it to keep the solution flowing or you may be dosing and then overdosing before the probe reads any change.
I use the outlet from my chiller to make all the solution move clockwise, which also helps keep roots away from pump inlets.
But then that is moot because I have a sample pot with my sensors in that takes a diverted portion of the solution so I can read better the temperature actually being delivered to the roots.
For full disclosure, I donât know it is more accurate, I suspect it might sample readings to eliminate noise. If you are coding on your own Arduino, you could do that in softwareâŚ
(although the analog input on an Arduino is only 10 bit AFAIK which will put limits on accuracy as well)
Way I see it is why would they make a continuous monitor if you had to move the probe in and out and unscrew the cap that holds the KCl.
They also sell a doser that by design should also be kept in the res.
I bought a Milwaukee recently to go with my combo. I needed Prime delivery and it was cheaper and the Bluelab replacement had terrible recent reviews of missing storage solution.
Works good. Was calibrated right out the box. The storage cap isnât clear so may keep the probe tip cleaner less algae. Takes 5-10 seconds to stabilize.
As PH is pretty critical, Iâve only ever used probes that sit outside of the res- the always in automation style were too rich for my blood.
One thing of note with online shipping of replacement probes is it will always get bad reviews in and around winter time. The storage solution will often freeze and leak and or shatter in cross country travels in much below freezing temps. These products with broken storage solution can sit around on shelves for months on end, as well.
I used to always keep a few packs of hach PH paper handy just in case I was doubtful. That said, I donât remember ever using them. Funny how many things are so much nicer to have and not need than need and not have. Sold a pair of double duct portable ACs and 1/10 HP chiller around 10 years back for a pretty penny. Today I wish I hadnât.
I have the same probe. I take my reading, rinse with tap water and use the ph 7 calibration solution to store it in. Recalibrate when the check mark goes away.
My last meter lasted for over 10 years doing this. It was a gro check, but same difference. The meter never died, I just got rid of it because I had stopped growing for so long.
Awesome info thanks, I have been eyeing off one of those cheap Chinese Arduino PH Sensors/shields and given the probes can be bought for $10, so long as they are reasonably accurate itâs a bargain.
Cheap pH meters are not a good idea for hydro. You need to keep the pH between 5.6 to 5.8 and itâs just too tight a range.
A cheap meter could easily be more than 0.3 off⌠not worth it in the end.
Thatâs been my experience with the cheap tds/ph meters that are all over eBay. itâs good to mess about with this stuff in a situation where it no big deal if it doesnât work out 
. Iâve got a cheap liquid sensor I have put on the floor of my tent to turn off the circulation pump if it gets immersed and setting up timers with relay shields is simple enough, but Iâd still like to put together a ph doser. Iâve seen some neat DIY ones in aquariums that seem to function well enough, I figure if they are keeping fish alive, a plant has to be achievable. ..
OK, an update. My Atlas probe is still running strong but the cheapo one has given up the ghost. It now reads too low with too low a slope for me to want to use it any more. It lasted about 2 1/2 years of what I would call good use. This is well over half of the claimed life of the Atlas probe at around 1/4 the price.
Can I just make a distinction between âa cheapo meterâ and âa cheapo probeâ at this point?
A cheapo meter will have very very cheap, possibly badly designed, electronics reading the also very very cheap probe. It will not calibrate well, or for long, it will not be stable.
If you buy in a reasonable PH circuit to read your cheapo probe, or make one yourself, it is very likely to be much higher quality than the circuit in the cheapo meter. The circuit is where a lot of noise and inaccuracy enters the signal, not the probe. If you get a good probe and a cheap probe and connect them to the same circuit you will see this yourself.
The cheap probe will have less reference solution inside and it will not be as well sealed though so it will not have as long a service life and will need calibrating a little more often, but nowhere near as often as the cheapo meter.
Basically, with a cheapo meter, you will be lucky to get an accurate reading at all. With a cheapo probe and a reasonable circuit, you will get accurate readings but you will need to maintain (calibrate) it a little more often than an expensive probe and it will have a shorter operating life.