# Environmental sensing and calibration

Canonical HTML: https://flavorotor.com/research/sensing-calibration
Machine-readable index: https://flavorotor.com/research/data/chapters/index.json



Calibration and verification requirements for pH, EC, temperature, level, light and rotation measurements.

In brief

Calibration and verification requirements for pH, EC, temperature, level, light and rotation measurements.

**Sensing architecture.** Original project diagram showing the intended data path. [I01]

**Prototype sensor assembly.** Internal build evidence; measurement traceability depends on the published calibration record. [I01]

## Measurement principle

A sensor reading becomes research data only when its identity, calibration, range, sampling interval, temperature conditions and failure rules are recorded.

## Minimum calibration plan

 |
 Sensor | Calibration/verification | Frequency trigger

 | pH | two- or three-point buffers bracketing operation; slope and offset retained | before a trial, after cleaning, on drift or according to electrode stability
 | EC | certified conductivity standard near operating range; temperature compensation checked | before a trial and after probe maintenance
 | Solution temperature | comparison with traceable reference in stirred bath | before deployment and on replacement
 | Level | measured-volume additions across working range | after geometry or sensor position changes
 | PPFD | reference quantum sensor/spectroradiometer mapping | after light, optics or geometry changes
 | Rotation | encoder or video reference across commanded speeds | after drive or load changes

## pH electrode model

 SEN-1 E = E 0 − 2.303 R T F   p H E=E^0-\frac{2.303RT}{F}\,\mathrm{pH} E = E 0 − F 2.303 R T ​ pH Ideal Nernst response of a hydrogen-ion-sensitive electrode; practical slope and offset are fitted during calibration.

**Explanation**The ideal electrode voltage changes linearly with pH. Real sensors still require measured slope and offset calibration.

## Calibration record

calibration_id, sensor_id, sensor_model, serial_number,
reference_standard, reference_lot, reference_value,
measured_value, solution_temperature, fitted_slope,
fitted_offset, residual, operator, timestamp, firmware_version

## Fault rules

 Out-of-range, non-finite, implausibly fast-changing or stale measurements disable automatic correction. The system logs the rejected value and the reason; it does not silently replace it with a plausible number.

## Traceability

Calibration records identify reference material, method, environmental conditions, corrections and uncertainty. [R38] [R39] [R43] [R46]

## References

- [I01] FlavoRotor project team (2026). FlavoRotor prototype implementation record. *Internal engineering report*.
- [R38] Joint Committee for Guides in Metrology (2008). Evaluation of measurement data — Guide to the expression of uncertainty in measurement. *JCGM 100:2008*. https://doi.org/10.59161/JCGM100-2008E
- [R39] Joint Committee for Guides in Metrology (2012). International vocabulary of metrology — Basic and general concepts and associated terms. *JCGM 200:2012*. https://doi.org/10.59161/JCGM200-2012
- [R43] International Organization for Standardization (2017). ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories. *ISO/IEC*.
- [R46] Heckert, N. Alan; Filliben, James J.; Croarkin, C. M.; Hembree, B.; Guthrie, William F.; Tobias, P.; Prinz, J. (2002). NIST/SEMATECH e-Handbook of Statistical Methods. *NIST Handbook 151*.