It is important to calibrate/adjust your pH meter (technically speaking to calibrate the pH electrode in the pH sensor) sooner or later, depending on how accurately you want it to measure. Calibration depends on the required measurements as well as application areas concerned.
For example, the accuracy of the measurement is very critical in industries like Life Science. As such, here, it is required to measure pH in regular intervals. On the other hand, in a wastewater treatment plant, since the pH of water in applications doesn´t change at a rapid rate when compared to the Life Science industry, calibration is not that critical.
What pH meter calibration?
If you calibrate a pH sensor, then you measure the value you receive in a known solution, usually a pH buffer, and control the difference. If you adjust a pH electrode, then you correct its current measurement value to a reference value, usually the one printed on the buffer bottle.
Simple, right? We commonly do the second point, adjustment, but we call it calibration. Before you start, make sure the transmitter signal won’t cause issues in your process when you disconnect it. Also, make sure you program your transmitter for the buffer solution(s) you use.
Speaking of which, you should have the following supplies:
- Cleaning solution
- Distilled water
- Clean beakers
- Buffer solution that you trust (two is better, if you have another)
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How to calibrate a pH meter
Examine the pH electrode
First, check the pH electrode for contamination or damage. If it’s damaged, then fix it or toss it. If it’s just dirty, then use the cleaning solution according to its directions. Whether you use acids, washing liquid, or alkali, choose a solution appropriate for your process and the contamination.
Flush the pH sensor
Next, flush your sensor with distilled water. Do this, even if you didn’t have to clean it, to rinse away anything that may contaminate the buffer solution you’ll use in Step 3. After flushing, dab or pat away excess water with the paper towels. Don’t rub; you might charge or damage the sensor.
Immerse the pH electrode
Fill a beaker with your first buffer solution, then immerse your electrode in it. I know it’s tempting to just drop the sensor directly into the buffer bottle, but you’ll avoid contamination and extend the life of your buffer if you use the beaker.
Calibrate the pH meter
Now you can start your calibration/adjustment. Keep an eye on the stability of the value; an old pH meter might react sluggishly. When the value stabilizes, set the device to accept this calibration/adjustment point.
Rinse the pH sensor and repeat
Flush the pH sensor with distilled water again, then immerse it in another clean beaker with the second buffer solution.
How often do I need to calibrate my pH meter?
How often you need to adjust the sensor depends on the following:
- Accuracy your process needs
- Stress your process conditions put on the sensor
- Sensor’s ability to withstand that stress
In a drinking water application, you can expect stable conditions, so you may only need to calibrate once a month. A measuring point with a high temperature or high pH might need a weekly tweak. Use your experience – or borrow someone else’s – and pay attention to the diagnostics your system provides.
Adjustments in the field sometimes come with environmental challenges. However, digital sensors make maintenance much easier. In many cases, the microprocessor that converts the signal can do more, like store the adjustment values in its memory. That way, you can bring the sensor into a lab or workshop, connect it to a suitable device, and perform your adjustment. Then you can either reinstall it or set it aside as a nicely adjusted backup.
A good pH meter calibration or adjustment will not only improve your process accuracy but also save time and money. Cleaning and adjusting your pH sensor properly will prolong its life, especially if you can do it in the workshop instead of in the field. Hope this guide helps those of you with pH sensors.
To know more about pH meter calibration, you can get in touch with our engineers.