How Do Iknow if Ph Meter is Working?

[Bassman2003]

Hello,

I have a General 7011 pH meter which I am unsure if it is working correctly but am not sure the best way to test it.

It calibrates just fine but a couple a batches showed mash pH's at 5 even. Unless my water changed drastically I would not expect that mash Ph.

So is there a best way to test the meter and see if it is working? I only take room temp measurements so I did not overcook it.

Thanks for your help!

 

[Qhrumphf]

How are you acidifying (if you are)?

I've had a few instances where I've carelessly contaminated my mash pH sample with lactic acid (thoughtlessly collecting a sample in the same cup where I held the lactic pipette) and had pH readings well below what what makes sense. Getting a second clean sample and retesting has corrected back to a sensible reading.

 

[passedpawn]

Make sure to let the sample get to room temp before measuring. They all probably correct for sample temperature (mine does, and I think that works well). But if you have doubts, best to let the meter and sample be at same temp.

 

[Qhrumphf]

Calibration temp should be the same as well.

 

[Bassman2003]

Hello,

I use lactic acid along with some calcium chloride or gypsum. Everything is at room temps.

My question is about how do check to see if the meter is working properly? If I put it in the buffer solutions it comes up with the correct number but the beers did not have very much acidification.

A recent pale ale had 1 ml lactic with .4 CaCl and .35 Gypsum in the mash and measured 5.0 on the meter at room temp.

Last water report is attached.

 

[schematix]

My Hanna pHep meter is the same way. If you measure it in the 4 and 7 buffers its pretty close, but its unbelievable at mash pH (about -0.3). That was a $100 down the drain.

My MW102 always measures with a few hundreds of the bru'n'water prediction.

If you're not sure if its the meter or a mash, another option is to get another buffer close to the brewing range. They make a ph 5.0 buffer. If you're crafty you can make a buffer of just about any pH you want too.

 

[Silver_Is_Money]

Make sure to let the sample get to room temp before measuring. They all probably correct for sample temperature (mine does, and I think that works well). But if you have doubts, best to let the meter and sample be at same temp.

It's likely that temperature correction is only intended to be reliable in compensating for sample temperatures that deviate perhaps 5-10 degrees F. to either side of the calibration temperature (I.E., room temperature). It would not allow sufficient compensation for a room temperature adjusted mash pH if you stick the probe into a hot mash.

 

[Qhrumphf]

Hello,

I use lactic acid along with some calcium chloride or gypsum. Everything is at room temps.

My question is about how do check to see if the meter is working properly? If I put it in the buffer solutions it comes up with the correct number but the beers did not have very much acidification.

A recent pale ale had 1 ml lactic with .4 CaCl and .35 Gypsum in the mash and measured 5.0 on the meter at room temp.

Last water report is attached.

How often are you calibrating? I find that I need to calibrate meter (I use a Milwaukee MW102) every day I use it. The way you're storing the probe can be an issue too.

 

[ajdelange]

So is there a best way to test the meter and see if it is working?

Do the stability check at https://www.homebrewtalk.com/showthread.php?t=302256

 

[Horseflesh]

If you are not getting the mash pH numbers you expect, is it possible that something is amiss with the grain input? Maybe your LHBS changed to a new batch of a base malt with a different L rating, for example. Though .3 is a pretty big change...

 

[Bassman2003]

Thanks for your replies. I will have another read over the cal instructions and look at the stability.

I calibrate right before I take the mash sample which is about 30 min into my Sacc rest. The Pale ale was brewed with Rahr malt, so I would think it would be as expected. I have used Great Western for this recipe in the past as well (before the meter).

So if I do stability testing and the meter seems to be responding well to calibrations and being dipped back in the buffer solutions, at what point do I say "I trust the meter"? I just can't image only adding 1ml of lactic acid to a pale ale and blowing through the pH target with my water. Maybe the local water has changed a bit? Maybe a LaMotte test kit would be a good Christmas present?

 

[ajdelange]

If your electrode passes the stability test then you can trust it. That is what the stability test is for.

I will note that if you have a mash going and add liquid acid to it the pH will plummet because the acid is dispersed through the liquid part of the mash first and the electrode is measuring the liquid. It takes a lot of stirring to mix acid added to mash thoroughly throughout the mash and then it takes time for the acid to reach the basic malt components that neutralize it or perhaps it is better to say that the basic elements in the grain take time to pass into the liquid where they can neutralize the acid. It usually takes 20 minutes or so for pH to stabilize completely after addition of acid or base to a mash.

 

[mabrungard]

It usually takes 20 minutes or so for pH to stabilize completely after addition of acid or base to a mash.

This is especially true if your wort isn't recirculating through your mash. It is exceptionally difficult to stir a mash and get it homogenized.

 

[Bassman2003]

Thanks. I add all of the acids and minerals to the water before adding the grain. I calibrate right before I take a mash reading. I will look into the stability test.