How to prevent pH meter use mistakes from occurring
pH meters can be a wonder for brewers, chemists, scientists and acid enthusiasts and kombucha makers alike but they sure can be finicky things to use and manage correctly.
Calibrate this, calibrate that.
Storage solution this, store in that.
Given the complexity and the science around their use, it's no wonder that user error can creep in and ruin a good reading.
In the case of quality pH meters, it's always good to follow the user instruction manual!
Here's a list of the most common user errors and mistakes that people sometimes make when using and storing their devices.
Storing the electrode 'dry' rather than in a proper storage solution
Electrodes are the sensitive parts of the pH meter, they do the hard work and are pretty complex scientific constructions.
Basically, they are designed to be kept wet because something-something science - the electrode will dry out, and be most likely rendered unusable if kept dry too long.
This is because a pH electrode’s sensing glass is generally composed of three distinct and discrete glass layers: a hydrated outer glass gel layer, a dry middle layer, and a hydrated inner layer.
The hydrated layers are responsible for giving the electrode the sensitivity needed to detect changes in pH.
If you fail to store your electrode in a fresh storage solution, you totally reduce the device's sensitivity.
This will mean drifting pH values can drift, you may be frustrated by slow response times from the unit, and obviously, you will get incorrect readings which means any judgment you make about your beer or solution will be founded on a lie.
A lie!
That said, there's many a chance that you can revive a 'dried out' electrode.
If you finally place the bulb and junction in some pH storage solution and leave for at least an hour, you may be able to revive it.
Assuming that works and you then want to use it (naturally!) remember to calibrate your pH meter before you test your sample.
Wiping the sensing glass
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| An original Beckman ph tester |
What you use to clean and how you clean the unit is very important.
The electrode works by sending a voltage to your meter that is based on the pH of the solution it has been placed in.
If you clean the glass probe by wiping it, say with a clean paper towel, the pH glass can produce a static electrical charge. This charge interferes with the probe's reading of the voltage which means the meter will give an inaccurate reading.
So, do not wipe the probes, let them soak in distilled or deionized water.
You can probably blot excess moisture off with a paper towel or cotton material how do not wipe it!
Not properly cleaning the electrode
If you do not clean your pH electrode regularly a coating known as the 'hydrated layer' may develop on the glass bulb. Once this layer settles in, it will cause your unit to display inaccurate readings.
Which just defeats the whole point of using a meter! So clean your electrode with a proper cleaning solution.
(in) frequency of calibration
Should you fail to regularly calibrate your pH tester, you will likely be greeted with completely inaccurate readings, and the longer you leave it, the more likely you will get incorrect numbers that mean the decisions you make are worthless.
Depending on the amount of use a unit gets, daily calibration may be ideal.
If you are an infrequent user, then you should probably consider calibrating prior to using your meter.
Having a low electrolyte fill level
Refillable electrodes allow you to replenish the electrolyte in the reference compartment once it begins to run down. If the electrolyte is not replaced as this occurs, your pH measurements will go awry.
The problem of 'erratic electrode response' is a common problem caused by inadequate electrolyte levels.
It's good practice then to ensure that your electrode is replenished and functional by maintaining the fill solution level at less than a half-inch from the fill hole cap.
Storing the electrode in deionized water
Never ever, ever store your electrode in water, even if you have run out of storage solution. It will render it useless.
In this case, it's all about the ions. You may remember them from chemistry class back in the day. is
An ion is a molecule that has a non-zero net electrical charge.
Got that?
Deionized water contains pretty much no ions. Your pH electrode is full of ions, both in the filling solution and in the hydrated part of the pH sensing glass.
So when an electrode is submerged in a solution that has no ions, the ions in the electrode will want to move out into the solution in an attempt to attain a new equilibrium.
Gradually the electrode will be spent of its ions and it will be unable to complete its task
If for some insane reason you have done this (which might be why you've found this page..?) there's a way you can try and fix the probe. If it is refillable, replace spent fluid with a potassium nitrate fill solution. Then place the electrode in the storage solution.
Give it a chance to do its thing.
You will then need to calibrate the unit before testing again.
Using an old electrode
It's odd that we have to state that it's a mistake to use an old dried-up electrode but there you go. A dry electrode will not have enough ions present to do the job and you won't get any useful readings.
Best, you get a replace probe - one that means the job - the round head style for testing with a beer wort or hydroponic solution and a conical head for 'solid' items such as soil.
Not fully submerging the probe in the solution
This is a pretty simple error to avoid. Make sure the whole pH sensing component and reference junction are submerged in your water, wort or other solution. This is so enough ions can be measured to enable a good reading.
In the market for a quality meter?
We recommend the Milwaukee MW102, a tried and true unit that suits the needs of beer brewers.
If you think all this is too much, you can always do a simple test with a pH strip.
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