BillyWu
Dutch Passion enthusiast
Hi folks. I usually try to follow scientific procedure when it comes to using analytical instruments, such as pH meters and PPM meters. I can imagine this guide will be particularly helpful to new growers and especially those in hydroponics 
Introduction
This little guide explains the principles of contamination and how to properly maintain and use your instruments. These principles are ESSENTIAL for accuracy when it comes to analysing various things, such as run-off pH, PPM/EC in water and even temperature/humidity
Instrument usage
pH meter - Ah, the essential tool in every grower's repertoire. The simple pH meter varies in size, price and functionality. Some come with in-built temperature probes as well as pH, and some even do PPM/EC, pH AND temperature all in one!
pH meters are VITAL to growing, as pH is very important to the plant. pH is the measuring of hydrogen ions which gives water acidity and alkalinity. I won't get into the exact science, but pH extremes can be VERY bad for your plant. pH 0.0 - 6.9 is considered acidic, pH 7 is considered neutral and pH 7.1 - 14.0 is considered alkaline.
Found online at Wikipedia, http://upload.wikimedia.org/wikipedia/commons/b/bb/PHscalenolang.svg
You can find graphs for what pH is best for your soil or soil-less medium, but generally pH 6.5 is best for soil and pH 5.8 is best for hydroponics. pH affects what nutrients your plant's roots can uptake from your reservoir or soil, so the closer you get it to these values, the better your plant will grow!
Found online at THCtalk.com, http://www.thctalk.com/gallery/data/500/user17219_pic14203_1233853343.gif
To measure pH for soil: Water your plant as usual. Pour enough water in to get roughly 10% of your initial watering volume as run-off from the bottom of the plant pot. The first few drops give the most accurate pH reading. Simply extract enough water to put your pH probe into, give it a little time until the reading stabilizes and doesn't move and that's your pH! If your find it is not at the desired value, Google how to change soil pH
To measure pH for hydroponics: Generally people extract a sample from their reservoir and measure that. I recommend you do not put the probe straight into the reservoir as that could possibly cause contamination from foreign substances, which I will get on to later. Extract a small sample from the reservoir and measure that instead. pH in hydroponics is easier to change than soil, just use a few drops of pH up or pH down!
Now, to keep your pH probe working optimally, it requires care and maintenance. Here are some points to get the best results from your pH meter:
PPM/EC meter
PPM or EC meters (same thing) measure the electrical conductivity (EC) or parts per million (PPM) in your water. What this means is how many total dissolved solids (TDS - basically salts) are present within your sample. The total dissolved solids values can be good or bad. EC is measured in microsiemens per centimeter (µS/CM). For hydroponics, EC is used to measure the strength of nutrients present in your reservoir. Example: Someone says they have an EC of 1.8 in their reservoir. This would be quite a strong nutrient solution and the values show there are a lot of nutrients present. You can find guides for feeding schedules for hydroponics and they should give you a rough guide to what your water EC should be. It should be checked regularly as EC and pH change in hydroponics very quickly and they need to be kept consistent.
Their usage and maintenance procedures are generally the same as the pH meter, except I don't believe they need to have their probes stored in water. They also require different calibration solutions, such as KCl (potassium chloride). The below chart is useful for converting EC to PPM.
Found online at Sensi Seeds forums, http://forum.sensiseeds.com/uploads/4/ppmChart-med.jpg
Contamination
This is quite a big one and it's generally good practice to understand the principle of contamination.
What is contamination? Contamination is when a foreign substance is mixed in with a sample, although it can apply to many things. It is generally the principle of something foreign getting mixed with something else.
Contamination can drastically throw your readings off. It is good practice to prevent contamination, and here is how:
Generally, just keep things separate from each other and keep them clean before using them for something different than what you were previously using it for.
I hope this guide helps you all! It's good practice to follow these procedures as precision accuracy is necessary to detecting problems. You don't want instruments that say your pH is 6.5 when it's actually 5.9!
Introduction
This little guide explains the principles of contamination and how to properly maintain and use your instruments. These principles are ESSENTIAL for accuracy when it comes to analysing various things, such as run-off pH, PPM/EC in water and even temperature/humidity
Instrument usage
pH meter - Ah, the essential tool in every grower's repertoire. The simple pH meter varies in size, price and functionality. Some come with in-built temperature probes as well as pH, and some even do PPM/EC, pH AND temperature all in one!
pH meters are VITAL to growing, as pH is very important to the plant. pH is the measuring of hydrogen ions which gives water acidity and alkalinity. I won't get into the exact science, but pH extremes can be VERY bad for your plant. pH 0.0 - 6.9 is considered acidic, pH 7 is considered neutral and pH 7.1 - 14.0 is considered alkaline.
Found online at Wikipedia, http://upload.wikimedia.org/wikipedia/commons/b/bb/PHscalenolang.svg
You can find graphs for what pH is best for your soil or soil-less medium, but generally pH 6.5 is best for soil and pH 5.8 is best for hydroponics. pH affects what nutrients your plant's roots can uptake from your reservoir or soil, so the closer you get it to these values, the better your plant will grow!
Found online at THCtalk.com, http://www.thctalk.com/gallery/data/500/user17219_pic14203_1233853343.gif
To measure pH for soil: Water your plant as usual. Pour enough water in to get roughly 10% of your initial watering volume as run-off from the bottom of the plant pot. The first few drops give the most accurate pH reading. Simply extract enough water to put your pH probe into, give it a little time until the reading stabilizes and doesn't move and that's your pH! If your find it is not at the desired value, Google how to change soil pH
To measure pH for hydroponics: Generally people extract a sample from their reservoir and measure that. I recommend you do not put the probe straight into the reservoir as that could possibly cause contamination from foreign substances, which I will get on to later. Extract a small sample from the reservoir and measure that instead. pH in hydroponics is easier to change than soil, just use a few drops of pH up or pH down!
Now, to keep your pH probe working optimally, it requires care and maintenance. Here are some points to get the best results from your pH meter:
- Fresh batteries are always the first thing! Make sure your batteries hold enough charge for your pH meter to function properly.
- Use your pH meter on a 'control' sample. A control sample is essentially a sample that you know the details of. Example: You have pH 7 water that you have tested many times. Put your pH probe into the pH 7 water and see if it comes up as 7 again. If you KNOW it's 7, but it shows a different value, you might want to move on to the next step.
- Buy calibration fluid! I VERY highly recommend getting some pH 7 buffer solution. This is essentially just a solution that is fixed at an exact pH which you can use to calibrate your pH meter with. It also makes a great control sample! To use it, simply put your pH probe in the buffer and if it doesn't show as pH 7, use the calibration function on your pH meter to set it.
- Keep your pH probe stored in water. Generally, pH probes need to be kept wet to keep them performing optimally. I recommend keeping your pH probe sitting in pH 7 water or pH 7 buffer.
- Clean it before use! ALWAYS make sure your pH probe is clean from your last readings before you use it on a different sample. Example: You have 2 plants. One has a pH run-off of 6.5 and the other is 6.3. If you just tested the pH 6.5 run-off, you don't want to be putting that into the pH 6.3 run-off as it will contaminate the sample with the pH 6.5 water. You want to clean it before you use it with a different sample!
PPM/EC meter
PPM or EC meters (same thing) measure the electrical conductivity (EC) or parts per million (PPM) in your water. What this means is how many total dissolved solids (TDS - basically salts) are present within your sample. The total dissolved solids values can be good or bad. EC is measured in microsiemens per centimeter (µS/CM). For hydroponics, EC is used to measure the strength of nutrients present in your reservoir. Example: Someone says they have an EC of 1.8 in their reservoir. This would be quite a strong nutrient solution and the values show there are a lot of nutrients present. You can find guides for feeding schedules for hydroponics and they should give you a rough guide to what your water EC should be. It should be checked regularly as EC and pH change in hydroponics very quickly and they need to be kept consistent.
Their usage and maintenance procedures are generally the same as the pH meter, except I don't believe they need to have their probes stored in water. They also require different calibration solutions, such as KCl (potassium chloride). The below chart is useful for converting EC to PPM.
Found online at Sensi Seeds forums, http://forum.sensiseeds.com/uploads/4/ppmChart-med.jpg
Contamination
This is quite a big one and it's generally good practice to understand the principle of contamination.
What is contamination? Contamination is when a foreign substance is mixed in with a sample, although it can apply to many things. It is generally the principle of something foreign getting mixed with something else.
Contamination can drastically throw your readings off. It is good practice to prevent contamination, and here is how:
- Don't mix your samples! If you're analysing two separate plants' pH, don't mix the run-off samples on your pH pen. Clean your pH pen after analysing one sample before dipping it in the other.
- Clean all of your instruments after use. Water will do fine. Residues can be left in pipettes and measuring apparatus that may be mixed in next time you put a sample into them. Think 'fresh apparatus', all clean and ready for use!
- When you're making up nutrient solutions, don't go using your measuring apparatus in different bottles. Example: I have some Grow and some Bloom nutrients. I want to add both to my water to feed my plant, but I don't want to contaminate the bottles. So what would I do? First I'd use clean apparatus to add one of my nutrients to my water, but before I go sticking the apparatus in the other bottle, I'd clean it first. I don't want to go using the pipette I just put in my Grow bottle with my Bloom bottle, as I'd be getting Grow in the Bloom bottle that way.
Generally, just keep things separate from each other and keep them clean before using them for something different than what you were previously using it for.
I hope this guide helps you all! It's good practice to follow these procedures as precision accuracy is necessary to detecting problems. You don't want instruments that say your pH is 6.5 when it's actually 5.9!
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