Your FYTA Beam measures soil moisture via the probes directly in your plant’s substrate. For this raw data to become meaningful moisture readings, the sensor needs a calibration — a conversion curve that defines which reading corresponds to which actual moisture level. This article explains what substrate calibration is all about and how you can use self-calibration to fine-tune it to your own individual substrate.
Table of Contents
1. What Is Substrate Calibration?
By default, you select a substrate type from a predefined list in the FYTA App — for example, potting soil, coconut coir, or orchid substrate. A general calibration curve is stored for each of these substrate types, and your moisture readings are calculated based on it.
2. Why Does the General Calibration Sometimes Reach Its Limits?
Substrates are natural products, and real potting soil mixes can vary considerably depending on manufacturer, composition, age, and additives like perlite, coconut fibers, or bark chips — in density, conductivity, and water retention behavior. A general calibration curve always reflects an average value for the respective substrate category. This works well for most standard substrates, but with mixes that deviate significantly, it can lead to moisture readings that appear too high, too low, or insufficiently differentiated — even though the sensor itself is working perfectly.
3. What Exactly Does Self-Calibration Do?
With self-calibration, you calibrate your sensor directly to the individual substrate in your own pot, instead of relying on the general, predefined calibration curve for your selected substrate type.
Here’s how it works technically: during self-calibration, the substrate in your pot is deliberately brought to what’s known as field capacity. This means you water it repeatedly until the substrate is saturated to the point where it can no longer absorb any additional water. Based on this saturated state, the sensor learns how your individual substrate behaves at maximum water availability, and adjusts the calibration curve accordingly.
4. For Which Pot Systems Is Self-Calibration Not Possible?
Since the process relies on deliberately, repeatedly saturating the substrate followed by clearly defined drying behavior, self-calibration doesn’t work in every pot system. It’s currently not possible with:
- Pots without a drainage hole at the bottom
- Self-watering pots with a water reservoir
- Semi-hydro systems using expanded clay in closed pots without a drainage hole
The reason: in all of these cases, excess water either can’t drain away, or the system maintains a permanent water reserve. As a result, no clear field capacity and no normal drying behavior can be established — both of which are necessary for the calibration to work reliably.
5. What Advantages Does Individual Calibration Give You?
Individual calibration leads to significantly more precise and reliable moisture readings, because the calibration curve is matched exactly to the real properties of your substrate — water retention capacity, conductivity, texture — rather than to an average value for the category as a whole. This is especially relevant for you if:
- you use a self-mixed or atypical substrate (e.g. your own soil-perlite blends)
- you use a very coarse substrate (e.g. orchid substrate with bark chips)
- your substrate deviates significantly from the average for its category
- your substrate is already somewhat older
- you’ve been noticing unusual or implausible readings with your current substrate type for a while
The general calibration curves already work well for most standard substrates — so self-calibration isn’t a feature you necessarily need to use. It’s rather the targeted solution for cases where the standard calibration demonstrably doesn’t fit your individual substrate.
6. How Do You Find Out That Self-Calibration Could Be Useful for You?
Our system has detected that your readings are behaving unusually — this, or something similar, is how the self-calibration prompt appears in the app. A banner appears above the moisture graph of the affected plant as soon as the system determines that self-calibration would likely improve your readings, because the general calibration for your selected substrate type doesn’t seem to match your actual substrate. In addition, the app displays a care tip on the home screen that also points out the option of self-calibration.
7. When Should You (Re-)Calibrate?
A (re-)calibration makes sense in the following cases:
- When you repot or change the substrate
- When the length of your probes changes, for example because you’ve repotted into a larger pot
- When your readings behave unusually
- When your initial calibration didn’t lead to any improvement in your readings and a sensor defect has already been ruled out
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