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Hydroponic Meters And Testing Equipment You Need To Know

Hydroponic gardens require a delicate balance of pH, chemicals, and nutrients to keep plants growing optimally. Having the right meters and testing equipment on hand to monitor your system is important to ensure healthy thriving plants.

Hydroponic Meters And Testing Equipment You Need To Know

Hydroponic gardens require a delicate balance of pH, chemicals, and nutrients to keep plants growing optimally. Having the right meters and testing equipment on hand to monitor your system is important to ensure healthy thriving plants. Test equipment only works well if it's maintained. Keep meters calibrated to ensure accurate results.


Why pH Meters are Important

pH meters generally return a value between 0 and 14 corresponding to how alkali (14), also known as base, or acidic (0) a solution is with 7 being a perfect balance between the two. It is possible to have negative pH and values higher than 14 due to how pH is calculated. Pure water has a pH of 7, meaning neutral, since it contains equal parts hydrogen (H+) and hydroxyl (OH-) ions. The pH of your hydroponic system is important for the uptake of nutrients by plants. Most plants can survive in a pH environment between 5 and 7.7 but prefer a range of 5.5-6.0. The reason for this is that as pH rises above 6.5, nutrients that plants need to grow begin to precipitate out of solution. As an example, iron loses roughly half its effectiveness at a pH of 7.3 and begins to cling to the growing walls and chambers. At a pH of 8, it is almost completely missing from the solution leaving plants to be iron starved. This is why it is important for any hydroponic grower to have a pH meter on hand. Since meters require calibration periodically and some require their probes to remain in an aqueous solution, it can be helpful to have a second backup on hand as well. Knowing these factors accurately allows gardeners to adjust the system up or down with pH adjusters in order to grow at their desired levels. Auto dosers continuously read the pH of a solution and adjust to a preset level by adding acid or base in order to maintain balance. They can also add nutrients as needed. They take a lot of the work out of making sure your hydroponic system is always at the perfect pH.

Find what you need in our selection from handheld meters to pH controllers and auto dosers.





PPM, TDS, & EC Meters

Hydroponic systems require a delicate balance of nutrients and salts to provide an ideal growing environment. PPM, TDS, and EC meters are vital to maintaining a stable system by showing total dissolved solids, electrical conductivity and parts per million of dissolved solids in solution. It is important to measure at the same times every day in order to keep consistent results. Under usual growing conditions, the reservoir EC should measure slightly lower than the grow media and runoff solution. If it is significantly lower this can indicate a salt buildup in the grow media. To correct this, leach your grow media with a diluted nutrient solution and replace with new. A general range for EC at various growth stages of plants is:

Seedling 0.8 - 1.3 EC

Clone 0.5 - 1.3 EC

Veg 1.3 - 1.7 EC

Bloom 1.2 - 2.0 EC

NOTE: These are just general guidelines, every plant strain varies.

See all TDS, PPM, and EC Meters


Also, for installations that are more remote, EC Shake offers a linear induction powered nutrient meter that you simply shake to charge up and use, no batteries required.

Combination meters are a great way to reduce the overall number of device you have to touch in order to take a reading of your garden. They save on space and time.

For those that grow in soil, there are a range of meters that can test pH, temperature, moisture, and combined N-P-K (Nitrogen, Phosphorus, Potassium) nutrients as well as soil test kits.



Meter Scales

There are a number of scales that meters report results in. Knowing your scale and what the scale your nutrients are measured in is critical to keeping your dosage within the manufacturers specs. PPM is a measurement of parts per million and is a dimensionless quantity meaning that they are reported with no unit of measurement associated with it. There are two main scales within hydroponics, the PPM 500 scale and the PPM 700 scale. The 700 scale is based around the potassium chloride (KCL) of a solution while the 500 scale is based off the sodium chloride (NaCl) content in solution, sometimes referred to as total dissolved solids (TDS). Individual nutrient molecules have different electrical properties. Only a chemical analysis can determine the true PPM of a solution and cannot be accurately measured by a CF or EC meter. Here are some examples:

500 Scale

2.4EC x 500 = 1200 PPM (500 scale) or 1200 PPM / 500 = 2.4EC

700 Scale

2.4EC x 700 = 1680 PPM (700 scale) or 1680 PPM / 700 = 2.4EC

It is important to know what scale your nutrients are measured in, what scale your meter uses, and the scale of your calibration solution. Below are some popular manufacturers and the scales they use:

Nutrient Scale


The good guys over at Bluelab provide a conversion chart as well as a calculator.

Conversion Chart


Meter Cleaner


All test equipment must be kept clean in order to ensure accuracy. Keep your meters clean and calibrated with cleaning products and calibration solutions. Meters should be calibrated every 2 weeks under normal continual use. Cleaning more often will ensure that calibration lasts longer and that cleaning times are minimized. Cleaning is not difficult when done regularly and the video below will demonstrate how to quickly clean and calibrate a common pH pen.

» Video: How To Calibrate A pH Pen


Replacement parts

From time to time probes and testing accessories need to be replaced. Probes are fragile, especially pH probes, therefore it's a good idea to keep several on hand, especially for those who rely on accuracy in large hydroponic systems as well as with nutrient auto dosers. There are a full range of replacement parts for maintenance for many brands including Autogrow Systems, Autopilot, Bluelab, Hanna Instruments, Milwaukee, Nutradip, Oakton and more.

Questions? Call 888-815-9763 or email [email protected].