Having a pH meter for home DIY projects can be a useful tool. We use our pH meter to test the pH in many of our hobbies. Things like homebrewing, charcuterie, cheesemaking, fermentation, gardening, and even some cooking all require accurate pH testing. A pH meter does require some care and attention in order for it to maintain it’s accuracy. Part of that involves proper calibration.
Over time and with regular use your pH meter will need to be calibrated to maintain it’s high level of accuracy. Today we will be talking about how to calibrate your unit, how often you should calibrate, and when you should change your pH buffers out. If you follow these steps your Apera Instruments pH meter will give you the most accurate readings for a long time.
Every pH meter is slightly different on how it’s calibrated but the concept is basically the same. When you calibrate your pH meter you are creating “Points of Calibration”. Each point of calibration that you create extends the range of accuracy for you meter. You can do a 1 point calibration, a 2 point calibration, or a 3 point calibration.
We will be using the Apera Instruments PH60S-Z for this demonstration (as it’s the one I have), but most Apera Instruments pH meters can be calibrated the same way. If you are in the market for a pH meter be sure to select the one that suits your specific needs. The main differences between each meter comes down to the probes. Some are better for liquids while others are better for solids. The unit I am using (with the spear tip) works extremely well in liquid or solid samples and it’s the one I recommend if you are into DIY projects, as this one unit can handle all that you can throw at it.
When it comes to calibrating your pH meter there’s really only one thing you need to know. “What is the pH range of the samples that I’m testing”. The answer to this question will help you decide on how to calibrate your unit.
Let me explain. There are 4 ways you can calibrate your pH meter and depending on what samples you are testing will determine which way you calibrate.
The first way is a one point calibration. This means you only calibrate using 1 pH buffer solution, the 7.00ph. When you do a 1 point calibration your pH meter the range of accuracy is limited to the 7.0ph area. So if you are testing samples where the ph is generally around the 7.0 ph you can get away with only doing a 1 point. Examples of things you might test with a 1 point calibration would be swimming pools, neutral soil, and aquariums.
If you tend to test samples that are more acidic (a pH of less than 7) then you will need to do a 2 point calibration. A 2 point calibration increases the range of accuracy for your ph meter. So to do a 2 point calibration you will start off with the 7.00 pH (this is your first point) then you will do a second point with the 4.00 ph. After the second point your pH meter will have been calibrated to be more accurate with acidic samples. This is the option I mainly choose as nearly all of my samples will have a target ph that’s less than 7.0. Examples of these types of samples are wine, beer, sauerkraut, salami, cheese, and kombucha.
On the other hand, if you test samples that are mainly alkaline (a pH greater than 7) you will need to calibrate your unit to be more accurate towards the alkaline side. If that’s the case you would do a 2 point calibration starting with your first point being 7.00ph and your second point being 10.01ph. Once finished you unit will have been calibrated to be more accurate with alkaline samples. Examples of these types of samples include urine, blood, seawater, cleaning ammonia, and baking soda solutions.
The fourth and final option for calibration is to do a 3 point calibration. This option is selected if you don’t know the range of the samples that you will be testing or you plan on testing both acid and alkaline samples. To perform a 3 point calibration you will simple enter the calibration mode and set your first point at 7.00 pH, next you will repeat the same steps to set the second calibration point at 4,00ph, then finally you will finish by repeating the same steps to set the third calibration point at 10.01pH. This allows you to have a pH meter that is accurate with a wider pH range allowing you to test both acidic and alkaline sample.
Something to consider
Most hobbyist will rarely if ever test alkaline samples in their projects. So, If you only test acid samples, it’s not necessary to do a 3 point calibration on your unit. A 3 point calibration is only necessary if you test both acid and alkaline sample.
How often should you calibrate your pH meter?
Your pH meter will come out of calibration over time and depending on what type of samples are being tested. My advice to home users of pH meters is to calibrate every time you use it. This is what I do and it guarantees accurate results. Besides the process only takes 60 seconds to calibrate. Alternatively, if you use your pH meter rather frequently you can always dip your pH meter into one of your pH buffer solutions (7.00 or 4.00) and see what the reading looks like. If the unit measures a reading that within 0.03 then you don’t need to calibrate and you can proceed with testing your samples. So here’s the example. If you dip your meter into a 7.00 solution and the reading either reads 7.03 or 6.97 then you are good to go, but if the reading comes back outside of that 0.03 range I would recommend calibrating the unit.
When should you discard the calibration liquids?
The standard pH solution have a shelf life and the accuracy of your pH meter is dependent on the freshness of your solutions. With this in mind it’s important to know when to discard old calibration solutions and replace them with fresh. The 7.00 pH buffer solution is the most stable and can last the longest. The 7.00 pH solution should be discarded after 5-10 uses (If you only use your pH meter once a month then you should always discard the old solutions and start with fresh solutions).
The 4.00 as well as the 10.01 ph buffer solutions tend to deteriorate a lot quicker. Therefore you should discard these solutions after every 2-5 uses (If you only use your pH meter once a month then you should always discard the old solutions and start with fresh solutions).
If you follow these practices of calibrating your pH meter you will have accurate readings for a long time. My suggestion would be to have extra refill containers on hand that are kept in a cool dark place. Depending on how you use your unit you can either get the 8oz refills or the 16oz refills (with a cal pod included). I buy the 7.00 pH refill and the 4.00 pH refill as I never test any alkaline samples.
Follow These Steps when calibrating your Apera Instruments pH Meter
- Start by pouring some of your pH buffer solution into it’s designated vial (or cal pod)
- Remove the cap from your pH meter and rinse in some distilled water, blot or shake dry.
- Power on the unit by short pressing the power button (top button on the control panel)
- Enter calibration mode by long pressing the calibration button (bottom button on the panel)
- Start by placing the pH meter in the 7.00 solution and give it a swirl. Once you get a stable reading (indicated by a smiley face) short press the calibration button to register the reading.
- Rinse the probe then blot or shake dry. You’ve just created your first calibration point.
- Next enter calibration mode again by long pressing the calibration button
- For your second point calibration you can either use the 4.00 solution of the 10.01 solution.
- If you are only doing a 2 point calibration then choose the solution that you want your pH meter to be more accurate in. For example I tend to only test acidic samples so I generally always just choose the 4.00 solution to finish a 2 point calibration. If you tend to only test alkaline samples you would choose the 10.01 solution.
- Once you place your probe in the appropriate solution, give it a swirl, and wait from a stable reading.
- As soon as you get a smiley face, short press the calibration button to enter the reading , rinse the probe, then blot or shake dry.
- If you are only doing a 2 point calibration (like I do) then you are finished and you can now test your samples.
- If you want to proceed to a 3 point calibration then enter into calibration mode one more time and insert your probe into the appropriate liquid (your probe will prompt you as to the options you have).
- Once you get a stable reading, short press the calibration button to enter the reading, rinse the probe, then blot or shake dry.
- You have now completed a 3 point calibration and you can now test your samples.
- ***WHEN YOU START THE PROCESS OF CALIBRATION DO NOT POWER OFF YOUR PH METER TILL YOU AR EFINISHED***
Here are a few things you might find useful when calibrating your Apera Instruments pH meter
- Apera pH Meter (with Bluetooth) PH60S-Z
- Apera Instruments pH meter (non Bluetooth version) PH60S
- Calibration Pod
- 7.00 & 4.00 Calibration Buffer solution refills (with free calibration pod)
- KimTech Delicate Wipes
Enjoy the video. If you have any questions feel free to ask away. If you make this at home I’d love to hear about how it came out!!
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