Leaving the pH probe in RDWC reservoir...?

Growroom Design
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#1

I was thinking here (i know, shouldn’t do that too much). Before i got into deep water, I would mix my food, pH the mix, and put the probe away in KCl storage solution.

Now, i find it a pain in the ass to take a reading then rinse and put the probe away twice a day. I’d much rather hit the button and walk away.

I am wondering if leaving the probe in the rez would shorten its service life?

I use Bluelab combo. Guardian uses the same probe, it even came with a suction cup for such mounting. But how often will I be replacing them? They last way over a year in KCl, and at $70 bucks a pop where i’m at, it matters if they only get 3 months.

Anyone have experience with Guardians and probe life, or any other real-time pH monitors that heave the probe in circulating solution 24/7? How often are you changing them?

Thanks folks
HH

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Looking for some help to design/build an automatic PH controller - cheap
#2

Generally, ideal solutions for cannabis are a little bit acidic.

I would buy the argument that anything left in solution, other than a plant, may begin to degrade.

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#3

No experience with the guardians myself but some thoughts that might be helpful:

I’ve had an “industrial” PH probe sitting in a relatively low-ec solution (circulating) for around six months and haven’t had any issues, stable PH readings. These particular probes are labeled for continuous solution contact.

For instance, https://www.atlas-scientific.com/_files/_datasheets/_probe/IpH_probe.pdf claims a life expectancy of 4 years (1 year cal) fully submersed in a salt solution.

For the Guardian PH probes, they state https://www.bluelab.com/Product-Manuals/Guardian-Monitor-Manuals/Bluelab-Guardian-Manual-ENG-JUL13.aspx :

The life time of a pH probe depends on the environment it is used in and the way that it is treated. To receive a long life from your pH probe, please ensure you follow the guide below.

They do not give an explicit estimation because it’s a function of the type of solution and how well the probe is maintained but would assume they have a relatively similar service life as other “industrial” type probes. They give a six month warrantee and a replacement probe has an OEM price of ~50USD.

But, as 99 says, the probes will eventually degrade. Clean, re-condition (in KCL) and re-calibrate them every so often (monthly for instance) to extend the service lifetime.

The primary mechanisms of eventual failure will probably be 1) fouling of the glass bulb with biological films, iron, or calcium 2) fouling of the reference junction 3) depletion of the electrolyte 4) biological growth in the glass bulb. Regular maintenance will extend the life by addressing these problems.

For the most part, PH probes will have a service lifetime and even the best will eventually fail or slow. The maintenance part play a large role on the duration of the service lifetime.

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#4

Thanks @Northern_Loki. Did not realize that biological growth in the glass bulb could be a problem. I run sterile so, hopefully, that is a mitigating factor. Atlas says dilute bleach can be used to clean films, so that will be getting done. I think i’ll try the following regiment:

  1. Each rez change, after pH is stabilized, clean and store/recondition the probe in KCl overnight, return to rez in the morning.
  2. Clean, condition and calibrate every 4 rez changes, bi-monthly, whichever comes first
  3. Buy another probe, keep it stored in KCl permanently, and use it to check the the functioning of the working probe every 3 months. If the first one starts significantly drifting from the reference, rotate them, and go buy a new reference probe.

Should be a good longitudinal case study

EDIT: I did find Bluelab’s instructions/specs pretty vague. That PDF from Atlas is much more informative

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#5

@99PerCent; i think so too. Just trying to figure out if the rate of degradation is warranted vs the cost of replacement. But it looks like it might be!

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#6

I have been looking at PH probes a lot over the last two years. Yes, leaving your probe in ‘extreme conditions’ will dramatically shorten its life. That said at the PH levels we deal with in hydro, being over 5.2, and the nutrient levels being as they are, they are not normally seen as ‘extreme’ by the manufacturer. I would not imagine you will shorten the life of your probe (assuming proper maintenance) by a noticeable amount if it was left in your solution.

@Northern_Loki I have one of those Atlas probes and I do not find it noticeably better or worse than the probe I got with an incredibly cheap Arduino PH sensor kit (entire kit was under £40). I have noticed probes generally last that long, although even that Atlas probe needs calibrating just as regularly as any other (they claim 1 year between calibrations).

The seal at the top of the probe on the Atlas seems better but for sensing, and lifespan, they seem identical. It may be that cheaper sensing circuits may have issues with cheaper probes, I do not know. I have been running both side by side for over a year now. They both have glass bulbs and they look almost identical except one has ‘Atlas Scientific’ printed on the side and the BNC on it looks a bit more expensive.

EDIT :

I am currently building one, and have been for two years now. Aside from times where I have accidentally broken the glass bulb, it is years between changes. I am still using the same probes I bought two years ago, and they show no signs of needing replacement running 24/7/365. On my Intellidose, I used the original PH probe for about five years before it drifted too far to be used.

After a year they all tend to drift a bit but not so much that it affects accuracy and most devices have a calibration setting to compensate for that. The interface for calibration is one of the next things I have to code.

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#7

Yes, I’m fairly certain that the Atlas is nothing more than a re-brand. I’ve seen something very similar in look and style for 1/3 the cost. Mostly for example purposes. Thanks for the durability/precision info re: arduino kit. Good to know.

This :point_up:. Though, regular maintenance is always a good idea (preventative). My probes do need cleaning as they do collect “stuff”.

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#8

This is great, thanks @MicroDoser. Hereby, in the hole she stays.

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#9

Pretty good plan, me thinks.

The biological growth in the glass occurs more in situations where the probe is somewhat abused, e.g. sitting at the bottom of a pond for 12 months. There are also somewhat dramatic ways to correct for such growth but typically they are just replaced since the chemicals used are a bit scary sounding.

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#10

I did look recently at the same place and they don’t include the same probe with the kit anymore.

All I would say in addition is to ensure no light is getting to your probe, especially the tip. Algae plays havoc with PH readings…

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#11

just install a tap at the bottom side

#12

Before I knew better, I’d just store my probe in ro water. But the probe would not read consistently after a week or two. Store the probe in kci storage solution, do urself a favor.

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#13

Well thats just the thing @Doulovebeef - I used to always keep them in KCl, but lots of pH monitor devices actually have a probe that stays in the rez 24/7, thus I’m curious how that will affect the proble life.

So far from the feedback I think the lifespan will be adequate, and the convenience is nice

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#14

The problem with distilled and RO water is that it leaches the ions out of the bulb solution quickly rendering it dead.

If you have a solution with a reasonable EC (like hydro) you should be ok. Condition it occasionally in KCL as per your plan. Or, when not in use, store it in the KCL solution. Never straight RO.

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#15

Any suggestions on where to look for the same probe, or another cheaper option that will work well? The Atlas sounds good, but the cost is too hi for me.

#16

This is the one that I currently use:


Already at 6 months life, barely needed any calibration after it stabilized. Note: I almost returned it at the first days at it not holded calibration, perhaps stored for too long/something. Now it is super stable.

I have this for replacement, not tested yet:
https://www.dfrobot.com/product-1074.html

The probe sits at the solution all the time in a pH/EC monitor.

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#17

This is the exact one I bought. It is still Incl. Tax: £26.82

In between posting about the probes and now, the cheaper one has started to become unstable and ‘wanders’ a bit more than it used to but the Atlas one is still going strong and staying stable.

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#18

Both of those look interesting. I like the reviews and your comments on the Milwaukee. I’ll add that to my list for sure.

Im glad to hear you have had good luck with that one. I had originally discounted it because of a comment I read somewhere about it not being suitable for constant immersion. Sounds like its working great for you though. At that price - including the shield - I may just go with it.

Thanks!!

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#19

I also read that and so I tried to be careful and not fully immerse it but reality had other ideas and it ended up fully under a few times but it did not seem to affect it.

It has been in nutrient solution constantly for over a year now and based on the life I estimated it to have when I bought it, the lifespan was not shortened.

I originally bought it as my very first, cheapest, way of reading PH using my own code. I was pleasantly surprised by the probe for the price. When used with better sensing circuitry it is far more accurate than when used with the supplied circuitry…

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#20

I used one of these “blue” chinese probes to monitor my reservoir solution in Brazil, it survived being immersed constantly.
The problem that I experienced was the need to calibrate a lot, sometimes more than once a week. The circuit was from a super cheap acquarium monitor, pehaps that was part of the problem.

Other times it was a lot more stable and not needed calibration. So the reliability of the readings where not great. But it survived these two growing cycles and perhaps could survive some more.
Of course this was my experience with a probe that can be from other manufacturer, it just looks as this one :slight_smile:

The Milwaukee that I have been using is rock solid, I check the need to calibrate and the deviations (when I get any) are normally at 0.1

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