HEBRARIUM

What the sensor thinks it knows

Temperature, humidity, pressure and the grower who believes the wrong number

Temperature
tells you how hot the air is.
Relative humidity
tells you how much water vapour the air holds compared with how much it could hold at that temperature.
Barometric pressure
tells you the weight of the atmosphere pressing on the space.

They are related, but they are not the same measurement.

A grower can understand temperature and humidity and still miss what pressure is showing: the weather system around the room, the movement of air masses, and sometimes why the environment feels unstable even when the thermometer looks calm.

Barometric pressure is not usually the first number
a small grower needs.

Temperature, humidity, VPD, air exchange, leaf temperature, substrate moisture and light matter more directly.

But pressure is not meaningless.

It can help explain weather shifts, storm fronts, changes in air density, changes in ventilation behaviour, and why an indoor room connected to outside air may behave differently from day to day.

The sensor is not giving you magic.
It is giving you context.

When two identical devices disagree

“ bought two identical meters.
They do not show the same number.

Good. Now education begins.

Two devices may disagree because one is bad.
But they may also disagree because of placement, calibration, sensor tolerance, airflow, radiant heat, battery condition, response time, condensation, dust, age, manufacturing variation, or because one sits closer to a leaf, wall, fan, light, intake, pot or wet surface.

A meter does not measure “the room”.
It measures the small piece of the room touching its sensor.

That is the first lesson.

Before blaming the device, ask: