Calibrating your pH pen and performing maintenance is extremely important to a successful cannabis crop. If you do not own a pH pen, you will want to by the end of this article. If you own a pH pen you will realize they aren’t without their troubles.
Owning a pH pen can create many problems such as inaccurate readings, early failure of probe and unstable pH reading. Calibrating your pH pen is only as good as the calibration methods and maintenance; therefor, the over all health of the probe. I will list a few key points that will help you calibrate your pen properly but also extend the life expectancy.
pH meter life span
Your pH pen is good for approx 12-18 months before the pen (meter) should be discarded. You can buy pH meters that have interchangeable probes AKA electrodes; in which, you can now extend the life expectancy of your pH meter. The pens that can be used to change your probe are serious to professional pH meters such as various Blue Lab and Hanna pH products. Some have various other functions and cannot be replaced such as pH, TDS + temperature all-in-one units.
Hanna H198100 Model
I personally use the specific growers Hanna HI98100 model. The price point is acceptable and I found to be the most reliable. The meter is also easy to calibrate your pen with two main calibration options. Options 1 is a two point calibration of 4.01pH and 6.86pH or Option 2, is a single point calibration of 6.86pH. You can also use calibration of 10.00pH as options but most follow instruction when promoted.
The Hanna H198100 model has an interchangeable electrode probe. The pH pen has a 1 button control and is simple to use. The instructions are easy to follow so I will not repeat the information. The Hanna pen is unique for several reasons.
- The pen has a hour glass meter that shows when the pen is measuring the pH. The hour glass symbol will stay illuminated every time it senses a pH change; it will stop measuring your pH if it does not sense a change in pH after 5 seconds.
- When measuring the pH prob will drop by specific increments which can help the grower understand how dramatically they are from their desired pH level. For example) I desire my soil-less pH level to be 6.4pH in vegetation and 6.2pH in flower. When I place my pH prob only 2 inches beneath the surface, my pH display will start counting down or up in increments of 1, 2 or 4. Closer I get to my desired pH level, the smaller the increment.
Most pH meters today have self calibration methods with a push of a button, so I will not say self calibration is unique and can be found on lower end models. As well as, most meters now come with double digit read outs making them within 0.02 accuracy.
Hydrate your electrode probe
When you first get your pH meter your pH probe will be dry. Its very important that you soak your pH pen within storage solution or at least your 6.86 or 7pH buffer solution for a minimal of 1 hour; some manufacturers call for 4-6 hours minimal
Calibrate your electrode probe
Once your probe has been soaked and hydrated it is time to calibrate. For most people, calibration between 4 and 7 is acceptable. You must make sure your calibration solution is stored within the correct parameters. Store conditions should be in a cool, dry place, making a grow room not an ideal to store your meter.
To calibrate your meter several important tips should be followed. You are required to follow your specific pens calibration instructions; in which, you know how to navigate the calibration options. Follow these steps below for the most accurate and successful calibration practices
- Make sure your probe is submerged in a clean 30ML measuring cup with zero debris. The calibration buffer must be new and not reused.
- When first stage calibration is complete, rinse of the probe with normal house water or RO water-never distilled water. Than your ready to dip your pH probe into your next calibration buffer of choice.
- After your pH pen is calibrated, rinse the pH pen under normal house water or RO water-never rinse with distilled water. Your pen is ready for use; do not take the pen from pH buffer to nutrient solution.
- Gently stir your nutrient solution until your pH stops fluctuating for approx 5 seconds. You can than assume your pH is generally accurate. Than wiggle your pH probe to see if the pH measurement jumps. If it does not, than you are accurate. If the pH measurement jumps than your pH chemistry is not balanced; and more time is required measuring.
- When done measuring your pH solution, rinse your pH pen with normal house water or RO water and place in storage solution. Storage solution can be placed within the cap or lid of pen.
- Never store your pH pen with distilled water.
- Never submerge your pH pen more than 2 inches below the water.
Getting an accurate pH reading
Getting an accurate pH reading with your pen can be tricky and does require some practice. Dipping your pH pen into the nutrient solution does not guarantee your accurate nor is it that simple.
First, dip your pH into the nutrient solution and hold stir gently mixing your water. Watch the pH scale up or down; keep stirring gently. It may take your pH pen 2-4 minutes to reach its accurate level. Ideally, its important to wait 5-10 minutes before checking your pH level when you initially add your first pH up or pH down to the nutrient solution; you must give it some time to balance the chemistry.
How often should I calibrate my pH pen?
Calibrating your pH pen fairly frequently is required. If you have to calibrate your pen every week because your nutrient solutions has humic acids than that is something specific to your calibration needs. Generally, if you pH your pen every two weeks you should be fairly accurate. But you must get to know your pen and the nutrient pH strengths your working with. You will discover what is normal and what is not after a grow cycle.
pH pen maintenance
Your pH pen will periodically require a maintenance cleaning. You can do this with a simply mild soap and water. With a soft bristle toothbrush, gently scrub the probe. You can also purchase a Blue Lab pH maintenance kit which is an all in one kit. The kit does include, storage solution, cleaning solution, multiple pH buffer packets for calibration as well as, mini tooth brush and measuring cups.
Maintenance should be done every time your pH probe looks dirty or after every crop. I generally put my pH pen into maintenance mode after each cycle because I mix water daily.
pH buffer solutions
The pH buffer solutions come in two packaged ways: in a bottle or single use mini packages. I am a huge fan of single use mini packages. I have several reason why.
- You waste very little each calibration compared to using the 250ML bottles.
- The packages have expiry date stamped on them.
- You don’t need to find clean containers or worry about cross contamination.
- You can insert your probe right into the package for measurement.
Always remember that your pH buffer solution does have an expire date and environmental factors will reduce the life span. Do not try and reuse the liquid. I tested that and found I was always 3-4 pH points off. In the pH world that is 30-40x more stronger or weaker; depends on how you look at it.
Beware of cheap pH pens
There are a lot of cheap pH pens on the market and its very tempting to purchase a meter with many reviews. I must admit, I have purchased many cheap pH pens in my growing career and I honestly, pH strips where almost as accurate. Never will I go back to a cheap meter-ever. Calibrating your pH pen is already annoying and finicky, its ever worse with a cheap pH.
The main issue with a cheap pH meter is: when calibrating your pH pen back to back, to double check accuracy, your pH meter may result in various calibration readings. Thus your now required to double check your pH accuracy by comparing pH nutrient solution read out with another pH pen. Using two pH pens is never fun nor is calibrating your pH pen several times.
I understand growing is very expensive and cost can easily impact your bank account or savings. If you can afford to make a grow room improvement, a pH meter should be a very serious consideration.
If you want to ready more about cannabis and pH water chemistry please review my blog about nutrient-feed-program + pH chemistry.