Master Calibration

Step 1: Prepare Master Sensors

Before any calibration begins, a set of pre-validated sensors, referred to as masters, must be set up. These are the baseline for all future calibrations.

• Add sensors to the system: Master sensors must already exist in Didge as active devices.

• Create a dedicated dashboard (e.g., “Master Sensors”) and group these devices (e.g., 20 master sensors).

• Device requirements: Use Dragino sensors (or equivalent) with both probe and ambient capabilities.

• Reference thermometer (recommended): Use a certified NATA (National Association of Testing Authorities) thermometer as a reference check during boiling and freezing calibration.

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Step 2: Equipment and Setup

• Access to crushed ice + water (for 0.0 °C reference) and boiling water (100.0 °C reference).

• Set the sensor transmit rate to every 1 minute using a bulk downlink command. This ensures timely updates for calibration.

• Wait ~40 minutes for sensors to reflect the new send rate in TTS.

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Freezing Point Calibration

1. Submerge the probe tip into an ice-water mix.

2. Navigate to the master device dashboard in the calibration section.

3. Choose:

   • Manual Method: Freezing

   • Tolerance (Probe): ±0.5 °C

   • Tolerance (Ambient): Disabled

   • Success Threshold: 5 (i.e., 5 consecutive valid readings)

4. Click Start Calibration.

5. The system checks if the sensor stays within ±0.5 °C of 0.0 °C for 5 consecutive readings.

6. Upon success, the session closes and is marked as calibrated.

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Boiling Point Calibration

Repeat the above steps, but with boiling water:

• Select Manual Method: Boiling

• Use the same tolerance and threshold values.

• Submerge the tip of the probe in vigorously boiling water.

• The system checks if the sensor stays within ±0.5 °C of 100.0 °C for 5 consecutive readings.

⚠️ Use proper precautions to avoid burns or cable damage during boiling tests.

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Why 0.5 °C Tolerance for Masters?

The ±0.5 °C threshold is deliberately strict. This tighter calibration tolerance is used to account for uncertainties inherent in reference methods (e.g., slight thermal inconsistencies in ice baths or boiling water altitude variations). Since these sensors will serve as reference standards, higher rigor ensures reliability.

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Calibrating Target Devices Against Masters

Once master units are certified:

• Use them to calibrate target devices in the field or production environments.

• In this stage, use a broader tolerance of ±1.0 °C, which aligns with:

  • Australian food compliance standards

  • FDA and international food safety benchmarks

The calibration module allows flexible tolerance settings, but these are the recommended levels for regulatory compliance and operational consistency.

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Recordkeeping & Certification

• Each completed calibration event is stored in the system.

• It’s strongly advised to retain the records for each master sensor’s calibration to establish traceability.

• Master units must be recalibrated regularly (interval based on your compliance program).