Plant Nutrition and Growth Enhancers

The Importance of Regularly Recalibrating Your Digital pH Meter

If you're one of those growers who errrrrr never quite finds the time to do the 'detail work' in your garden, maybe this will inspire you!

Every hydroponic grower needs to be acutely aware of the importance of managing his nutrient solution's pH. The acidity / alkalinity of your nutrient solution directly affects the solubility of various compounds that make up your nutrient solution. The pH scale quantifies the amount of hydronium vs. hydroxide ions in your water. These ions are a bit like plane tickets! Each one represent opportunities for different compounds to 'jump onboard' and become dissolved in the solution.

Remember: Elements need to be fully dissolved in water before they can enter your plant. When an element (or more commonly, a compound of that element) is fully dissolved it is joined with water at the molecular level—only then can it pass through the Casparian strip—a band of cell wall material discovered by Robert Caspary that acts like a Homeland Security officer for your plants!

So, this brings me to pH meters. I currently use two: 

The Horticare by Trans Instruments is a great budget meter. It's been well used (and a little abused) over the last year but it's still doing great. Some budget meters don't last more than three months—not this puppy. 

HM Digital pH-200. This is my favorite pH meter. It's got a few really neat features. First off, it's water resistant so if I accidentally drop it into my nutrient tank it'll keep working. I've lost countless pH meters to slippery wet fingers—I'm glad those days are finally over. It shows the temperature of my nutrients—that's very handy. I was surprised at how warm my nutrients had become outdoors. Next year I'll invest in a chiller. The pH-200 also measures pH to two decimal points. Pretty neat—definitely strokes the geek in me although whether this has any practical benefits... maybe! pH is a logarithmic scale after all so even the tinyest difference means more than you might think.

This brings me on to the need to calibrate your pH meter every week. I know, I know, it's a drag—and doing it every week sounds like a regular drag—but, bear in mind that professional growers will calibrate their meters before each use! So, once a week isn't a bad compromise for us ... less rigorous hobbyists now is it?

Why You Should Calibrate Your pH Meter For Hydroponics Every Week!

You may be surprised by how much the readings from your pH meter can change over time and continual use. We show how easy it is to keep your pH meter accurate and your nutrient solution optimal!

Recalibrating Your Digital pH Meter for Hydroponics

The good news is — recalibrating your digital pH meter is easy! Well, it is with the Horticare and the HM Digital pH-200 anyway. All you need is some calibration fluid (I'm using pH 7.01 in the video) and a few seconds. Calibration fluid is simply a solution that has been specially manufactured to a guranteed pH—it's the external benchmark you need when doing any sort of calibration activity.

HM Digital's pH-200 has an automatic calibration feature which senses which type of calibration fluid you are using. I only use one type of calibration fluid in this video. Many growers swear by using two-point calibration. That is, they calibrate their meters to pH 4.0 and pH 7.0. I use pH 7.0 only because it's closer to the sort of target pH I'd want for hydroponics. (5.5 - 6.5)

As you can see in the video, both my meters were way out, measuring around 7.5 when they should be reading 7.0. That means that I was inadvertantly mixing up my nutrient solution to be more acidic than it needed to be. Okay, I'll admit it, I hadn't recalibrated for over two months—it's easy to get lazy. Hopefully this video will inspire you to treat your pH meters with a little more respect than I did!

One final word of advice. It's absolutely crucial that you keep the probe in your pH meter wet—not dry! You need to pour a little probe storage solution in the cap after each use. While I make up my own storage solution (just a little acidic water at pH 3.5) HM Digital recommend you purchase professional storage solution from your local indoor gardening store—it's inexpensive and tailor made for the job.