Digital pH meters

Scott,

I have this one which is a very nice unit.....

http://www.hannainst.com/usa/prods2.cfm?id=002004&ProdCode=HI 991401

I used to leave it in one place (mounted) but it is pretty responsive when moving the probe around...

 

Any ph meter should be ok, i use one that has the pH probe and Temp probe seperate, some come combined in one.

Just ensure that you calibrate it. i do it once a week on water change.

 

Scott,

All that info is in the link I provided

They do include TWO fluids for a low and high calibration... It is easy to calibrate and the instructions are very clear...

By doing a dual stage calibration it ensures a better accuracy rate,,

Just have to watch the probes that they don't get algae covered....

I wiped mine weekly.. not sure if a quick excel dip would hurt, but never tried it...

 

The pH meter is indeed a fairly simple circuit but some are built better then others. The nicer ones will have a temperature probe and automatically compensate the pH reading for the temperature but this isn't critical for our use. Some will also have a 3 point calibration vs. a 2 point. I'd expect the 3 point calibration to be more accurate & more expensive but again, not critical for our use. The probes on the other hand come in a wide variety of quality & design but you can be sure any bargain unit will come with a cheap probe if it comes with one at all. Cheap probes run ~$50 and will last up to a year but probably less. A "double junction" probe would be slightly better for our purposes but they cost a bit more.

As for the calibration solution, this is the only option that makes any sense in my mind: http://www.hach.com/hc/browse.exploded.category.products/PRODCAT0640/NewLinkLabel=pH+Buffer+Pillows
They are powder pillows that you mix with distilled water to give you your calibration / buffer solution. These are by far the cheapest unit cost and are lab grade quality.

Here's a great site for more info on pH meters & probes: http://www.ph-meter.info/

 

deleted deleted

 

It's not about clogging them. It's about preserving the reference solution. The two junctions are in series, not in parallel, if you will. A single junction probe will allow the ions in the reference solution to leech out of the probe much faster. For in-line / continuous monitoring of aquarium water this is a real issue because the probe is constantly submerged in aquarium water vs. in a lab setting where the probe may be used for a few minutes to take a reading and then placed back into a storage solution. Ultra-high dollar probes will allow for draining & refilling of the reference solution & thus a much longer life-span. Even fancier probes use a salt bridge instead of a permeable junction. As far as clogging the junction goes, the worst thing for our inexpensive probes is to leave the bulb exposed to air long enough for the junction to dry out. That can ruin a probe in a matter of minutes.

 

hmm, since we only need a general reference, that still sounds like too much hastle. I think I will just stick with the drop checker and AP test kit. I only want to see if a change occurred since we use other methods to determine proper CO2 levels ie...proper PH.

 

I don't find mine to be a hassle at all. I mean, calibration is quick & easy and surprisingly only needs to be done every couple of weeks for me. Even though pH is a poor reference of CO2 using hardness charts it's still a fine reference once you learn what pH your water is with 30ppm CO2. For instance, I know that at 6.55 a couple of my fish start gasping at the surface. 6.60 is a safe number. I can see that number lit by LED all the way across the room which is doubly nice considering I'm horribly color blind and determining what is green isn't always easy for me. That pH meter has saved my fish from poor CO2 adjustments twice now.

 

Check this out.

For aquarium use, my Milwaukee and Pinpoint pH probes are double junction and they aren't lab grade. I have a Hanna pH probe too and it is a double junction probe as well.

But, a few years ago I took some biotech courses at the local college. Their lab probes were all single junction. LOL

 

Thats a good point. Assuming that KH2PO4 ppm is generally constant for instance, you will know what ppm CO2 a certain ph is in your tank. Using color does suck. Morning light makes the drop checker look one color and then aquarium lights in the afternoon make it look another. There's no way to see the color difference between 6.55 and 6.60.

Another toy to buy.. Thaanksss!