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Help me calibrate my PH probe?

badbread

badbread

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Ok, I'm stumped.

So I got a RK2 for Christmas a few days before I went back home for the holidays. I rip it open set it all up, blah blah. I got a bunch of packets of calibration fluid for the PH probe and followed the directions.

Calibration attempt 1:
1. Take off the cap that keeps the tip wet
2. Rinse it in RO/DI
3. Rip open the 4 calibration fluid, set the RK2 to 4 and wait for a stable value. Thing is when I did this the first time it stayed around 450 and never moved up or down. I set it in at that value.
4. Rip open the 7 calibration fluid, didn't rinse the probe in RO/DI and waited for a stable value.
5. Re-installed in tank in the back chambers where there is constant flow.

With this I thought I was good, PH read between 7.8 and 8.2 for a while but then started drifting way up into the 8.45 range.

Calibration attempt 2:
1. Rinse it in RO/DI
2. Rip open the 4 packet, wait for a stable value. This time the number went way down into the 250's on the RK2. I waited until it stabalized and then locked it in.
3. Rinse in RO/DI again.
4. Rip open the 7 packet, wait for a stable value and locked it in.
5. Test the probe in the 7 Solution and it reads 7 right on the nose on the RK2.

This attempt my PH was hovering in the 7.6 range mid day.

Calibration attempt 3:
1. Float the 4 and 7 calibration packets in tank water for about 1 hour thinking maybe the colder temp of the fluid was throwing off the readings.
2. Rip open 4, wait, lock in
3. Rip open 7, wait, lock in
4. Rinse in RO/DI
5. Test in the 4 solution and it reads 4.01
6. Rinse in RO/DI
7. Test in the 7 solution and it reads 7.0 on the dot.
8. Rinse and return to another constant flow area in the back of the tank.


This is what the tank is currently set at now and its reading around 7.8

Shouldn't it be a lot higher than that during the day like somewhere around 8.2?

Is there something I'm doing wrong while calibrating or something I should do better?

Thanks,
Jay
 
Current.png


PH Graph:
PHGraph.png



Current stats, should be a new image every time it loads.
 
I think most people use 7.0 and 10.0 solution to calibrate the pH probe. I don't see anything wrong using 4 and 7 though but not too sure.
 
I know when I calibrate my Pinpoint pH meter; I have to place it in the solution, a long time, to get it to quit drifting. And I am suppose to go back and forth between the two pH calibration samples until I can actually place it in each one and not adjust the dial anymore.

Do you run a calcium reactor? If you do, your pH will be lower.

What about testing your pH with a test kit, just to see where it states your pH is. Dip strip or something.
 
It also depends on if you are doing a 2 point or 3 point cal. If you have the lab grade you would be doing a 3 point cal.
You would just add the 10.0 pH cal fluid to what you have been doing. If you have the standard pH probe do a 2 point cal at 7.0 and 10.0.
 
Thanks for the replies all!

Ravie, the RK2 software runs a web server, I have a dedicated laptop right next to the tank that runs it, the RK2 software basically creates a new image every 10 seconds or so and the image gets pulled from that machine.

Mike, I stopped by that aquarium store in Dublin today and picked up 7 and 10 solution, good to know its available in the city as well.

Vento, it's the standard grade pinpoint one.

So, on the calibration packets it gives temperatures and then (what I'm assuming) is how accurate the solution is at those temps. Should I float the packets in tank water for a while and then calibrate?
 
FYI what I do, is I pour the stuff into bottles (combined a few things gotten from the last bar swap), so that I don't have to rush out and spend another 3 bucks every time I want to calibrate my probes... don't know how effective it is, but it sure is cheap :D

But yeah, what the packet says is what the pH of that solution is for any given temperature, IIRC 77°F is 7.01 and 10.01 respectively, I'd float them if you cared that much about accuracy, however if you look at room temperature it's not terribly different, so might not make a big whoop to you.
 
SFSU- You can do that for awhile, but eventually you will get contamination and it wont be as accurate. I don't know how much change but at my work we just change out fluid every couple of weeks. Granted we have cal fluid in 1 gal jugs so changing out a couple of oz. at a time is no big deal.

Bad- You will be fine doing just a 2 point cal. Like others said do the 7.0 and 10.0. And for temp correction, What it means when they say it is temp corrected is when you have a temp probe to go with the pH probe. The meter will compensate for temp of the fluid. Its really not that big of a deal when we are talking about stuff at room temp. I honestly wouldn't really worry about it too much.
 
I believe you are supposed to calibrate 4 with 7 or 10, not 7 with 10. But I am not sure if that really makes a difference.

What do the RK2 directions say about all of it? I would do what they say. :D

FWIW, my pH gets to 8.5 during the day, so I think your first calibration may have been just fine.
 
Well just to inject an extra bit in here... you always want to calibrate as closely around the numbers that you are expecting. Now I initially said 7 and 10, because your pH should be in that range, however if one of the probes is being used for a calcium reactor (which I didn't think of because I don't use one :D) then calibrating around 4 and 7 won't be too bad since you'll be just below 7 in your reactor chamber IIRC.

Vento: Yeah I figure I'm contaminating them, but I just want a general baseline to go by as the actual level of my pH is not super critical unless it goes WAY out of whack, so if I drip kalk and I see some large spikes then I know to stop, that sort of thing.
 
Yeah, I used 7 and 10 because I don't have a cal reactor. I use the little one time use package that they sell. Toss it away after you done. Can't contaminate it :) ..

So how important pH level really is?? My pH drop to 7.6 at night and goes up to 8.2 when the light kick in. I don't really see any problem with my tank.
 
I'm curious as well Elite, I mean I've always read PH should be between 7.8 and 8.2(4), and there should be a swing, etc.. etc... but I'm not sure why.
 
The pH swings because of photosynthetic activity. More CO2 at night, so lower pH.
I don't think its all that important at all - you just want to ball park it. One of the most insidious things about pH testing is the fluctuation, which often results in people trying to control their pH which is a losing battle and can end up doing more damage than good.

I almost never check my pH. Before I got a monitor, I never did (after my first year back in reefing). I was, however, very happy to have the monitor when I overdosed kalk because it very quickly let me discover what happened.
 
[quote author=sfsuphysics link=topic=5802.msg72839#msg72839 date=1231174042]
Well just to inject an extra bit in here... you always want to calibrate as closely around the numbers that you are expecting. Now I initially said 7 and 10, because your pH should be in that range, however if one of the probes is being used for a calcium reactor (which I didn't think of because I don't use one :D) then calibrating around 4 and 7 won't be too bad since you'll be just below 7 in your reactor chamber IIRC.

Vento: Yeah I figure I'm contaminating them, but I just want a general baseline to go by as the actual level of my pH is not super critical unless it goes WAY out of whack, so if I drip kalk and I see some large spikes then I know to stop, that sort of thing.

[/quote]

I was about to say. Most meters now-a-day uses two-points calibration and like sfsuphysics says, should be calibrated in it's working range. I am using meters to read my display tank as well as my Ca reactors and calibrated them differently due to the non-linearity of the slope/offset deviation each range has. This is much important as the probe gets older so I do it more often once it hits 6 months age.
 
Just checked with Randy - calibrate with fluids that span the expected range. 7 and 10, or 9 if you can find it for reefing.

Thanks for making me check!

:D


Oh

http://www.advancedaquarist.com/issues/feb2004/chem.htm
 
[quote author=Thales link=topic=5802.msg72846#msg72846 date=1231176455]
The pH swings because of photosynthetic activity. More CO2 at night, so lower pH.
I don't think its all that important at all - you just want to ball park it. One of the most insidious things about pH testing is the fluctuation, which often results in people trying to control their pH which is a losing battle and can end up doing more damage than good.

I almost never check my pH. Before I got a monitor, I never did (after my first year back in reefing). I was, however, very happy to have the monitor when I overdosed kalk because it very quickly let me discover what happened.
[/quote]

Knowing PH is most important when you dose stuff like kalk or have a CA reactor. I hadn't used mine in a while (I HAD a crappy CA reactor) I was happy to find it again, but not happy when the probe busted in my hands...but you have to replace the probe every year or so anyway.

I'm trying a small CA reactor (the cheapo Via Aqua Acro-Cal) which is tiny, but I got it for $30 on sale and I have the CO2 equipment from my crappy eBay reactor ... so I ordered the generic PH probe from bulk reef supply. If you use a CA reactor, you need really the PH monitor to dial in the reactor. Otherwise, I went a few years without knowing what the ph in my tank was.

V
 
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