pH Meter Calibration

[Hannabrew]

Which model Omega meter are you speaking of?

Omega PHH-7011

 

[jpb2716]

That's the meter that I have. I love it. If you're only doing 12 or so batches a year, you won't need to change out the probe for many many years

 

[ajdelange]

I wouldn't count on that. Electrodes tend to age out rather than wear out. That said I've had electrodes go more than 5 years. I wouldn't count on that though.

 

[Hannabrew]

So I purchased the Hach Pro Plus and did my first brew with it. I think I did everything right and after taking a ph reading 15 min into the mash (after a good stir) my reading came out to just about exactly what Bru n Water suggested it would be.

Since I use a cooler mash, one thing I'm struggling with is how to take these ph readings without losing heat. From what I've read I need to wait until at least the 15 min mark to take a reading and potentially should be taking it more than once yet everytime I open the lid I'm letting out a ton of heat and I noticed my mash dropped 2 degrees from just one reading.

Any suggestions?

 

[ajdelange]

Hole (normally closed with a stopper of some sort) in the lid and a wine thief?

 

[Hannabrew]

Hole (normally closed with a stopper of some sort) in the lid and a wine thief?

I suppose that's a good plan but then I'm breaching the lid. I guess it boils down to if the multiple pH readings are worth the potential temp loss of altering my lid?

I'm assuming a reading in the beginning of the mash after a hearty stir is not good enough right?

 

[rprego]

I've been thinking about the same issue... Would there be any reason that taking a sample from the spigot on the mash tun wouldn't work?

 

[Hannabrew]

I've been thinking about the same issue... Would there be any reason that taking a sample from the spigot on the mash tun wouldn't work?

My thought is that the water that pools under the FB is not a good example of the rest of the mash. And that's even with some pump recirculation in the beginning of the mash. When I go to vorlauf it is usually clear for the first pint or so.

 

[ajdelange]

A hearty stir or two or seven throughout the whole mashing process is a good idea from the POV of the mash itself but also in terms of getting a representative pH reading. This is the problem with drawing from a single point (i.e. the output tap which is otherwise a good suggestion) but obviously, in a situation where even opening the lid results in excess heat loss, is not a good idea unless one were to open the lid, take the sample, add a bit of boiling water, stir and close the lid. If you can't do that (too full) it would be a good idea, both from the POV of mash performance and sample integrity, to pick up the cooler and slosh the contents around before taking a sample (wine thief or spigot).

 

[Hannabrew]

I like the idea of adding some boiling water each time I open it. I suppose I'd have to figure out what works for my setup. Could I just "borrow" from the sparge water?

 

[Hannabrew]

Where did The Forum land on storage of the Pro+? I've seen a couple of differing opinions posted and didn't know if there is a consensus amongst the group. I'm currently storing it with a bit of RO water however it is drying up quickly so I'm concerned about it drying up and me not knowing until it's too late

 

[Hannabrew]

I'm going to assume the advice is still to store in the cap with some water.

I tried doing a stability test last night and realized how much of a noob I am at this. I have a few questions I was hoping to get answered.

1) If my storage water dries up, what is the best way to rehydrate the bulb? 10-15 minutes in tap water?

2) I'm using premixed buffers and I realize that for calibrating I will always want fresh buffers however for the stability test do I need fresh buffers for each testing? If so, it seems like I'll use my whole bottle before the stability test is through!

3) How do I know when a reading is stabilized? When I put my meter into the 7 solution for calibration it started at 7.12 and gradually kept climbing down and never seemed to stop. I gave up when it was at 6.91. Every time I thought it had stabilized it would drop another tenth. This was over the course of about 5 minutes. It never stayed on any given reading for longer than a minute though.

4) When rinsing with DI water, how important is it to get all the water out of the sample cup? I've been pretty OCD about it but I'm wondering if I need to be...is it the PH of any risidual water we're worried about affecting the buffer or the dilution of it? As for the meter itself, I've been spraying it and as AJ mentioned just using a paper towel to wick at it without putting any pressure on the bulb.

5) Once I calibrate 7 and 4 and save, shouldn't my reading be 4.00 if it's still sitting in the buffer? I was getting 3.99 (which I realize is within the accuracy range just thought it would show exact right after calibration).

6) When I put the meter in the sample, should I move it around before locking the cap on or lock the cap on and then shake it around?

7) I RTFM and didn't see anywhere that mentioned where we could find the slope/offset values on this meter...correct me if I'm wrong. If we don't know what it's using, how do I know that the meter is calibrated any given time I turn it on? Do I just plan on calibrating every day/time I use it?

8) with ATC, do I need to be concerned with the temperature at all when recording the readings? I will always cool my samples down to room temp (~70F) but want to make sure that the slight variances shouldn't matter. Assuming ATC accounts for temp differences, why do we need to chart temp when doing a stabilization test?

9) Other than spraying with DI water right after use, is there any need for cleaning solution? I think I read in this thread it was unneeded but just wanted to verify.

I think that's all for now. Thanks in advance.

-pHNoob

 

[ajdelange]

I'm going to assume the advice is still to store in the cap with some water.

Yes.

1) If my storage water dries up, what is the best way to rehydrate the bulb? 10-15 minutes in tap water?

Or RO water or DI water or 7 buffer,

2) I'm using premixed buffers and I realize that for calibrating I will always want fresh buffers however for the stability test do I need fresh buffers for each testing?

You want fresh buffers each time you run a test but for a single test just put the electrode in 4 buffer, stir occasionally and record displayed pH.

3) How do I know when a reading is stabilized? When I put my meter into the 7 solution for calibration it started at 7.12 and gradually kept climbing down and never seemed to stop. I gave up when it was at 6.91.

You record every 5 minutes or so. What you are looking for is it stabilizing. It should stop stabilize after a few minutes. An erratic history is indicative on an unstable meter/electrode and one that is, therefore, innaccurate.

Every time I thought it had stabilized it would drop another tenth. This was over the course of about 5 minutes. It never stayed on any given reading for longer than a minute though.

Not a good sign. The sticky has a plot from a stable meter.

4) When rinsing with DI water, how important is it to get all the water out of the sample cup? I've been pretty OCD about it but I'm wondering if I need to be...is it the PH of any risidual water we're worried about affecting the buffer or the dilution of it?

Yes, it is responsible for 'dilution error' but that shouldn't amount to a hill of beans. Turn the cup upside down and rap it on the counter. That should get 99.9% of the rinse water out.

As for the meter itself, I've been spraying it and as AJ mentioned just using a paper towel to wick at it without putting any pressure on the bulb.

Should be fine.

5) Once I calibrate 7 and 4 and save, shouldn't my reading be 4.00 if it's still sitting in the buffer? I was getting 3.99 (which I realize is within the accuracy range just thought it would show exact right after calibration).

Were the noise figure of your meter 0 and the electrode perfectly stable, yes. O/W no. A drift of 0.01 is perfectly acceptable as long as you stay near 3.99 for a half hour or hour or two.

6) When I put the meter in the sample, should I move it around before locking the cap on or lock the cap on and then shake it around?

Either.

7) I RTFM and didn't see anywhere that mentioned where we could find the slope/offset values on this meter...correct me if I'm wrong.

Don't believe this meter displays either. That is usually a feature of more expensive meters.

If we don't know what it's using, how do I know that the meter is calibrated any given time I turn it on? Do I just plan on calibrating every day/time I use it?

Yes, recal, or at least do a cal check, every time you use it. When the electrode wears out the meter will tell you it can't cal.

8) with ATC, do I need to be concerned with the temperature at all when recording the readings?

Yes, because the pH of the buffers change with temperature. Try to hold buffer temp constant during a stability test.

9) Other than spraying with DI water right after use, is there any need for cleaning solution? I think I read in this thread it was unneeded but just wanted to verify.

I have not found it necessaary even with electrodes I have used for years but that doesn't mean that you won't.

 

[Hannabrew]

Thanks AJ...so since this is brand new, should I reach out to Hach about exchanging it since it doesn't appear to cal properly (constantly drifting downwards)?

 

[ajdelange]

Yes, I would.

 

[z-bob]

I finally bought a pH meter -- the Hach Pocket Pro+. I was surprised that it only had one little packet of 7.00 buffer solution (I thought there would be a packet of 7 and a packet of 4 so you could do a 2-point calibration). So I'll need to buy some buffers sooner than I expected. What are the shelf lives of premixed buffers, a year? 2 years? Not sure what size bottles to get, 250ml or 500ml.

 

[day_trippr]

I have the same meter. If you fill to just below the line on the sample cup, that's 10 milliliters.
If you brew 20 times a year and check the calibration every session that's 200 ml.
I've been buying sets of 250 ml bottles here.
They have at least a one year validity period. I think that might be typical of pre-mixed test solutions...

Cheers!

 

[z-bob]

Link doesn't work. How about these?

https://www.amazon.com/dp/B01F7OXRG2/?tag=skimlinks_replacement-20
https://www.amazon.com/dp/B017H73794/?tag=skimlinks_replacement-20

I thought it took a lot more than 10ml per sample.

 

[day_trippr]

DOH! Apologies for the stupid link trick (fixed).
This three solution kit is what I've been buying...

Cheers!

 

[user 246304]

Used to use another set of (Nelson-Jameson) buffers, and never stored in storage solution - stored in pH4 solution, though I think I did titrate make up a solution at some point.

Any thoughts on this solution (I'm getting the Hach as well, though I used to use the Extech).

 

[z-bob]

DOH! Apologies for the stupid link trick (fixed).
This three solution kit is what I've been buying...

Cheers!

Thanks. Do you actually use the pH 10 buffer? That one is perishable; it's a carbonate/bicarbonate buffer and readily absorbs CO2 from the air.

If you need a high-pH buffer, you can make your own 9.18 solution from borax and distilled water (1.9 grams per 500ml of water) and mix it fresh every time.

I'll order the Biopharm 7 and 4 buffers, and just do a 1-point calibration this weekend while I'm learning to use my new toy.

 

[day_trippr]

Sorry, I totally missed the above post & question way back in October.
If @z-bob is still around...the answer is one of my meters (Hanna phep 98128) doesn't support 3 point calibration so for that one I only use the 10 to check the high end of the meter's scope. My other meter (Hach PP+) does support 3 point and I do use the 10 solution for that meter just on GPs.

Speaking of which...I went to calibrate my Hach last night and it was stuck on ~4.53 no matter what I dipped it in.
Finally took an actually look at the sensor...

Yeah, I don't think that's gonna ever cal again

Don't know how I managed that - I'm a hard-core tool guy across numerous disciplines and take care of my stuff. I even use a Fluke IR gun before sticking a pH meter in anything if there's any chance of over-temperature exposure (cheap insurance) and yet this barely two year old probe went to Meter Heaven the hard way...

Cheers!

 

[mabrungard]

Houston, we have a problem.

 

[ajdelange]

My other meter (Hach PP+) does support 3 point and I do use the 10 solution for that meter just on GPs.

Don't know what GP's are. I'll point out, though, that your meter assumes linearity between buffers so that, for example, if you are checking mash pH there is no point in calibrating against the 10 buffer. Calibration data derived from 10 buffer are used only for measurements between 7 and 10 pH.

 

[day_trippr]

"General Principle"
I use my pH meters for more than brewing, so knowing that a meter's scope is accurate at testable points is reassuring...

Cheers!

 

[day_trippr]

I got a nice scare when an allegedly brand new replacement sensor for my PP+ arrived direct from Hach's Amazon presence - with a reactive slope that was roughly 1/∞. So slow it couldn't really be calibrated as the reading wouldn't get with .5 of any sample. Eventually I tried accepting the readings anyway, but when the cal routine ended the meter immediately started flashing the "SENSOR?" error.

FML, I thought whatever took out the original sensor took out the meter as well! I tried using the Hach probe cleaner but even with a 2 hour soak there was no change in behavior. Sat down and had a beer while pondering what just happened, and realized it had to be a defective sensor, so I boxed the probe back up and went through the AMZN replace & return sequence.

Two days later the replacement for the replacement showed up and this one is perfect. And wicked fast - switching samples through the cal routine it was already reading within a few hundredths of the next sample before I had the cap back on the bottle. It's actually faster than the original probe ever was.

So the $75 bitch slap wasn't without a small bonus...

Cheers!

 

[Hannabrew]

I tried calibrating my Hach pH meter today and was surprised to find that even after multiple calibrations, it's still not reading the 4.1 sample correctly...it's reading around 3.95 or so. It reads the 7 solution just fine.

This pH meter is less than a year old and has been reliable up until recently. I just so happen to have another brand new Hach (long story) so I decided to give that a spin...same result.

Could my 4.1 solution be bad? I did just get new bottles.

 

[ajdelange]

It doesn't matter if the buffer is bad. The meter thinks it is at 4.01 and adjusts slope and offset so that it reads 4.01 initially even if the pH is, in fact, 3.95 (which, for a buffer labeled 4.01 ± 0.02, it could be). Initially is in bold for a reason. Intitially your meter thought the pH of the buffer was 4.01. It doesn't now. It thinks it is 3.95. Thus represents a drift of 0.06 pH in however long it was between the time you calibrated and the time you rechecked the buffer. Read the pH calibration Sticky in this forum and carry out the stability check described there.

Now the fact that two meters behave in exactly the same way is unlikely. That doesn't mean it can't happen - just that it happens rarely. A new meter will often exhibit strange behaviour on the day it is commissioned but should settle in quickly after that. The stability test is designed to help you diagnose problems like this. Try it and let us know what happens.

 

[Hannabrew]

I thought it should read 4.01 even if solution was bad but then I'm really confused...both of my meters and now a buddy of mine's meter (same model) are all reading the same after a fresh calibration. So that's 3 different hach meters reading 3.95 after calibrating with that same solution to 4.01. All at ~72F.

I have done the stability test on main hach a few months ago and it was rock solid...the problem with testing it now is it fails the very first test seconds after calibrating it so is it even worth doing the subsequent tests.

 

[ajdelange]

This is getting weirder. Yes, it is still worthwhile to leave the meter in the buffer and observe what goes on over a few minutes time. If it stays steady at 3.95 then the electrode is stable. You just didn't wait long enough before accepting the cal reading. Be sure to monitor that when you do calibrations and be sure the reading is stable before pressing the button to accept it. With a new meter it should be pretty stable after 30 seconds but even with a new meter it is worth while to wait a further minute or even 2 before accepting cal.