pH and TDS Meters: Which to Buy and How to Maintain Them
A pH pen and a TDS meter together cost less than a bag of nutrients and prevent more problems than any additive you can buy.
What to buy
A digital pH pen with automatic temperature compensation and two-point calibration, plus a basic TDS/EC meter. Avoid combination meters at the low end — they do both jobs poorly.
Calibration
Calibrate monthly with fresh 4.0 and 7.0 buffer solution, or any time readings look implausible. Buffer solution expires once opened.
Storage is what kills pens
The glass bulb must stay wet in KCl storage solution. Storing dry, or in distilled water, permanently damages the probe within weeks.
Using them
Mix nutrients first, then measure TDS, then adjust pH last. Rinse the probe with plain water between readings.
Frequently asked questions
- Do I need a meter in living soil?
- Less critically, since living soil self-buffers, but knowing your water's starting pH and ppm is still worthwhile.
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