# Ph Meters



## Carpman (8 Dec 2016)

I'm assuming that Ph meters are better than liquid tests and are more convenient.
Are they worth it ?
Any reccomendations ?


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## KipperSarnie (8 Dec 2016)

I prefer them because I find trying to ID the reading against a colour chart almost impossible.
I use one from EPorter ltd via Amazon £31 far superior to a cheapie from eBay which I also have.


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## AverageWhiteBloke (8 Dec 2016)

It's a dilemma I often find myself facing. For sure PH pens are going to be more accurate than liquid test kits because it will tell you what the ph is as oppose to what you think it is if that makes sense? Liquid tests depend on the lighting and I would say confirmation bias. As in if you feel your tank co2 is high you will probably see that with a liquid test and convince yourself. However PH pens are also only as accurate as you make them. Realistically if you want to feel for sure that your test is correct you would have to test with a known sample before and after. Generally ph4 and ph7 are used. They also need cleaned regularly.

The issue I had was obsession, you start fussing over .2 which in reality is nothing. Then you start thinking should I trust this meter because it was only £10 on ebay. From what I have read and going by some of the more experienced scapers the Hannah meters seem to be highly regarded but then you're starting to get in the £100+ bracket. Something I've been considering for a while but I worry I'll start worrying about that .2 difference again 

Just my opinion, but in answer to your question I think they are more accurate if used properly.


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## sciencefiction (8 Dec 2016)

AverageWhiteBloke said:


> From what I have read and going by some of the more experienced scapers the Hannah meters seem to be highly regarded but then you're starting to get in the £100+ bracket. Something I've been considering for a while but I worry I'll start worrying about that .2 difference again



I was drooling at a 200 euro Hannah TDS/Ph pen combo pen the other day....


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## rebel (8 Dec 2016)

http://www.ebay.com.au/itm/Auto-Cal...149323?hash=item25ba863c0b:g:uGkAAOSwqfNXjIAI

Might be enough for our purposes. You need to calibrate and store them properly.


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## rebel (8 Dec 2016)

or this one with the solution sachets.
http://www.ebay.com.au/itm/Digital-...871584?hash=item2ef8c0a9e0:g:2c4AAOSw-0xYR8Di


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## jolt100 (9 Dec 2016)

I bought a Voltcraft meter at £58 inc probe and have been very pleased with it. hope this link works.. 

http://pages.ebay.com/link/?nav=item.view&id=121594920180&alt=web


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## dw1305 (9 Dec 2016)

Hi all, 





sciencefiction said:


> I was drooling at a 200 euro Hannah TDS/Ph pen combo pen the other day....


I've bought some of these for work. There is a potential problem with them, in that the storage solution for the pH electrode is a very "salty" 4 mol KCl ( mol KCl = 74.56 gl-1)solution. 

You have to be very thorough in rinsing off the electrode (in DI water) before you use the probe to measure conductivity, as even the smallest trace of the storage solution left on the probe will raise the conductivity reading.  

cheers Darrel


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## dw1305 (9 Dec 2016)

Hi all, 





jolt100 said:


> I bought a Voltcraft meter at £58 inc probe


That looks OK.

cheers Darrel


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## AverageWhiteBloke (9 Dec 2016)

sciencefiction said:


> I was drooling at a 200 euro Hannah TDS/Ph pen combo pen the other day....


I think I know which one you mean, I have my eye on the same one. Something I'll probably treat myself to one day when I'm feeling flush. 
I got a combination TDS ph pen off ebay for around £25 but unfortunately the TDS side wouldn't calibrate down to the levels I'm dealing with, it seemed to be designed for higher values. I ended up buying another TDS meter for £7 which turned out you couldn't calibrate at all even though it showed the calibration hole in the image. I emailed them and they asked if I wanted a refund or a new one so I said if the new one will calibrate I'll take one and they sent another which also wouldn't calibrate. When I emailed them again English clearly wasn't their first language and I eventually just gave up. Ironically all three meters I now own give roughly the same reading even though I have no idea if it is the correct one  I sort of just take the average as it's not that important more of a guide. 
Now the PH side of the first meter seems to be fairly accurate. I can calibrate it prior to profiling my ph levels throughout the co2 on period then test t pen again at the end and it's still in calibration. 
Looking back though that was £30 I could have put towards the hannah. Never has the saying you buy cheap you buy twice rang so true.


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## papa_c (9 Dec 2016)

Interesting discussion, the issue with pH pens is maintaining the accuracy, the electrode needs to be kept wet in storage solution which is simply not di/RO water. I have a hanna combo pH/tds pen which was great to start and because I did not store it in the solution it now loses calibration within a week, need to replace the electrode at a cost of about £60.

I Bought a cheap £10 pH pen off of eBay and it does the job as we are not looking for accuracy to the 1/1000. I simply verify the accuracy against a pH buffer solution prior to using it.

I also have a pen probe linked to raspberry pi which is in the tank permanently reading pH every 20 minutes and emails a profile on a daily basis to monitor, it also runs my dosing pumps for EI to build it cost about £100 including making the circuit boards myself, it is my escape project while the boss watches EastEnders!  Target will be to post this to DIY project section when I get a spare hour or two


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## dw1305 (9 Dec 2016)

Hi all,





papa_cee said:


> Interesting discussion, the issue with pH pens is maintaining the accuracy, the electrode needs to be kept wet in storage solution which is simply not di/RO water. I have a hanna combo pH/tds pen which was great to start and because I did not store it in the solution it now loses calibration within a week, need to replace the electrode at a cost of about £60.


That is it really,  pH meters are quite high maintenance bits of kit. If people use them properly; two point calibration in pH7 and pH4, or pH10, buffers before every use and store the electrode in the correct molarity storage solution etc, they will get ~ accurate results, if they don't they won't.

You can buy solid state <"ISFET pH meters">, which simplifies electrode storage, but they are quite expensive to buy and there are still some issues.

cheers Darrel


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## KipperSarnie (9 Dec 2016)

How accurate do we really need?
I use ph4 & ph7 calibration fluid & calibrate only when I need to compare ph from an outside source that has been tested with a different meter.
Most of the time I'm comparing ph between tanks for the movement of fish so if both / all tanks read about the same (below ph7) then as far as I'm concerned all is ok.
If the ph is not in my desired range then I will also calibrate before sampling all again.


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## papa_c (9 Dec 2016)

For me I am only working to one decimal place. I feel 1/100 of a point movement is somewhat irrelevant in the hobby, for measuring CO2 by the 1 point drop whether it is .95 or 1.05 has little difference.


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## dw1305 (9 Dec 2016)

Hi all,





KipperSarnie said:


> How accurate do we really need? I use ph4 & ph7 calibration fluid & calibrate only when I need to compare ph from an outside source that has been tested with a different meter.


The problem is that pH is a really strange measurement, it is both a log10 scale and a ratio. As you move towards pure water pH becomes less and less meaningful as a measurement. 

cheers Darrel


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## sciencefiction (9 Dec 2016)

Interesting discussion...I need a new TDS meter.. Would anyone recommend a specific good one, regardless of price...links if possible.  It must be as automated and easy to use as possible. My old one cost 20 quid and did well for years but just stopped working all of a sudden. I am dropping the Ph/TDS meter combo idea...I don't need my Ph tested that much as it hasn't bulged in years  I though it would be handy though but sounds like too much hassle.


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## papa_c (9 Dec 2016)

Here's the one I bought, includes calibration sachets as well, not water proof but seems ok to me.....

https://www.amazon.co.uk/gp/product/B01J9KSOFY/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

Cheers, Chris


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## papa_c (9 Dec 2016)

It's that cheap you can stick it on the Christmas list as a stocking filler


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## papa_c (9 Dec 2016)

Stupid me, need to read more carefully after two glasses of wine! If its TDS you want try this one

https://www.amazon.co.uk/EZ-Digital...UTF8&qid=1481322392&sr=8-2&keywords=tds+meter


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## dw1305 (10 Dec 2016)

Hi all, 
Conductivity meters are a lot more straight forward than pH meters, so even a cheap meter will give you a reasonably accurate result. Any meter that offers low range (0 - 999 microS or 0 - 1999 microS) and automatic temperature compensation will give you a reasonably accurate (within ~10 microS) result.  

All TDS meters are really conductivity meters, they just use a conversion factor (usually 0.64 ~ 100microS = 64ppm TDS) to estimate TDS. 

You should be able to get a low range meter for ~£50.

All conductivity meters basically have 4 electrodes (ideally platinum coated), 2 outer and 2 inner, and an AC current is applied to the outer pair of the electrodes and then the amount of current (potential) between the inner pair is measured. Pure H2O is an electrical insulator and sea water has a conductivity of about 54,000 microS.

You can also easily make up your own calibration solutions from KCl (0.01 M KCl = 1411 μS at 25°C). Although I very rarely need to re-calibrate the lab. conductivity meters.

cheers Darrel


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