# How often do you replace your PH probe?



## m.lemay (Jul 28, 2002)

I just replaced my old one that came with the Milwaukee unit it was there for 21/2-3 years. It was way overdue. It still worked but the response time was slow,like you said, but what also happened is that the sensitivity or repeatability was off making somewhat unreliable. I would say that after 2 years i should have replaced it. Slow response I can deal with but inaccuracy, no way. I replaced it with a Broadley James probe from Drs foster and smith, I think I paid $29 for it.


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## KevinC (May 24, 2004)

OK, I don't have a pH probe in my tank, but I use many of them at work. The ones we have allow you to replace the fill solution (there is a collar with a hole in it near the top - empty it out, rinse with ion-free water, and replace from a bottle that came with the probe). Depending on the type of reference electrode, the solution is either saturated KCl or 4M KCl saturated with AgCl. 

I suspect the slow response might be fixed by replacing the fill solution. If the probes don't have a hole for refill, check a scientific supply place and buy one that does - up front it will be more $$, but in the long run it would be a lot cheaper.

Kevin


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## magicmagni (Nov 7, 2003)

That's something I may look into next time Kevin. The old one that was in my tank had no fluid in it so I guess it just runs out of fluid over time.


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## Jackfrost (Jan 8, 2005)

I must be setting a record. 3 years !

I clean it in a dilluted 50% denatured alchool 50% water solution using a small soft brush. It takes while but once I am done the bulb is crystal clear. I re-calibrate and off we go.

Its a Milwaukee SMS MA911 probe.

No delays and is right on.

As I said...shocked !

Nick


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## Momotaro (Feb 21, 2003)

> I clean it in a dilluted 50% denatured alchool 50% water solution using a small soft brush. It takes while but once I am done the bulb is crystal clear. I re-calibrate and off we go.


Those are the very same instructions I got from Milwaukee! That cleaning/decontaminating method works like a charm. 

Mike


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## magicmagni (Nov 7, 2003)

Do you folks using the Milwaukee notice that the reference solution inside the probe dissipates over the service life like Kevin describes? Wondering if this is just a thing that happens with the type of probe that pinpoint uses and if so if the Milwaukee one is interchangeable with the one I have- assuming it is better. Mine uses a BNC connector to the unit.

See what started this whole thread for me was that toward the end of the service life of the probe the relays in the unit that triggered the C02 solenoid would click on and off rapidly when the PH was right on the edge of the trigger point of 6.67 This was very annoying.


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## m.lemay (Jul 28, 2002)

I wouldn't say that the Milwaukee probe is better than the Pinpoint. I'm pretty sure all the PH probes are interchangeable, at least all the ones I've seen are.

Marcel


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## Jackfrost (Jan 8, 2005)

Marcel you are correct. probes are interchangeable.

Soloution wise I use the pinpoint 7 and 4 for calibration. The 4 is to adjust the slope. I find that after the initial calibration on the unit, the slope error will not affect the range of ph 6.5 to 7.5 that most aquarists are interested in. In four years my slope error has never drifted by more than 0.1.

I would have liked the Miliwaukee even more if it had two significant figures of resolution rather one. That is one thing I like about the pinpoint ph controller.


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## shalu (Jan 16, 2003)

I haven't cleaned and recalibrated my pinpoint probe for more than two years, since I got it. Have not noticed any slow down in response.


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## magicmagni (Nov 7, 2003)

shalu said:


> I haven't cleaned and re-calibrated my pinpoint probe for more than two years, since I got it. Have not noticed any slow down in response.


That's amazing. Now you got me all jealous. LOL 

Well I checked with American Marine and they say that it should be replaced every 10 months....so according to them I'm right on track, but now thinking about it I'm figuring that this recommendation is based on a probe in saltwater ,which is a more corrosive environment.

I though about refilling the probe with solution like Kevin describes above, but honestly don't want to hassle with all that I think. That probe for $29 that m.lemay brought up sounds reasonable. I wonder how that one is holding up? Sure beats paying $50 every 10 months.


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## Jackfrost (Jan 8, 2005)

Does anyone know who has the best price on a pinpoint controller ?


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## KevinC (May 24, 2004)

magicmagni said:


> That's amazing. Now you got me all jealous. LOL
> 
> Well I checked with American Marine and they say that it should be replaced every 10 months....so according to them I'm right on track, but now thinking about it I'm figuring that this recommendation is based on a probe in saltwater ,which is a more corrosive environment.
> 
> I though about refilling the probe with solution like Kevin describes above, but honestly don't want to hassle with all that I think. That probe for $29 that m.lemay brought up sounds reasonable. I wonder how that one is holding up? Sure beats paying $50 every 10 months.


Fill solution is available from Fisher Scientific (www.fishersci.com), catalog #SP138-500 or #SP135-500 (depends on the type of reference electrode) for $23.30 or $26.80 - this is a 500ml bottle - enough for YEARS of cleaning/refilling the electrode. In combination with the surface cleaning mentioned earlier, the pH probe might outlast you! Their electrodes are a lot more than $50 though - starting at about $103.

There are a few electrodes out there that use a "gelled" fill solution - this would be a lot more difficult to replace, but the claim is these are "low maintenance".

Kevin


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## Momotaro (Feb 21, 2003)

> Does anyone know who has the best price on a pinpoint controller ?


Why Pinpoint? You can get a Milwaukee SMS 122 for about $75!

Thats a good price!


Mike


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## Jackfrost (Jan 8, 2005)

I already own a Milwaukee.

I wanted to try a pinpoint for my 90G.

Nick


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## Aftica (Nov 26, 2003)

*Probe compatibility*

Anyone able to tell me offhand if the Pinpoint replacement pH Electrode / probe will fit *and* work on the Milwaukee SMS122 controller?

Where I live it's much easier to get the Pinpoint probes than the Milwaukee or Broadley James probes.

Thanks...


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