Measuring & Control — Thermo-hygrometers

Temperature and humidity belong measured together, because between them they decide how hard a plant transpires. At the same temperature a plant in dry air loses water far faster than one in humid air, and neither number on its own shows you that difference.

The sensor hangs where the plant is

A meter lying on the floor or just inside the zip is not reading the climate your crop is standing in. With an external sensor the probe sits at canopy height while the display stays outside the tent. That is not only easier to read: the moment you open up, the humidity you were trying to measure changes. The Fertraso Thermo-hygrometer is built for this and reads indoor temperature, outdoor temperature and humidity through a sensor on a 1.5 metre cable, so you also see the difference between inside and outside the tent at a glance.

The Garden Highpro range

The three Garden Highpro models step up in equipment: the Basic for a single reading, the Medium with an external sensor, and the Premium as the most complete of them. What you are buying here is mainly whether the probe can hang separately and how much you see at a glance, rather than a difference in accuracy.

Watch for the memory

One reading a day tells you little, because the problem usually sits in the hours you are not there. Once your lamps go off the room cools and relative humidity climbs, and that is exactly when mould gets its opening. A meter that remembers the lowest and highest value shows you in the morning what happened; check per model whether it does, because in practice it is the feature you use most.

Measuring is not yet regulating

These meters show what is happening and do nothing further. If you want your extraction to respond on its own to a temperature or humidity that has climbed too far, that is a controller rather than a meter, and those are under Climate Controllers. In practice you use both, because you set a controller to the values your meter has shown you.

Frequently asked questions

Where do I hang the sensor?
At canopy height, out of direct lamp light and out of the airflow from your intake or a fan. Both give a value that is true for that spot but not for your crop.

Why does my humidity climb at night?
Because the room cools while the same amount of water stays in the air. Relative humidity is relative to temperature, so your lamps switching off lifts the percentage on its own without any water being added.

Can I measure soil moisture with this?
No, this is about air. Moisture in your pot or substrate is measured with a tensiometer or a moisture meter from Soil Meters.