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Instruments & Calibration

Measured variables describe the instrument that analyzed them, in analyzing_instrument, and how that instrument was calibrated. Some variable classes require a specific instrument type, and each instrument type requires its own calibration type, so the right calibration fields come with the variable.

Instrument Hierarchy

graph TD
    AI["AnalyzingInstrument"]
    AI --> PHI["PHInstrument"]
    AI --> CRMI["CRMInstrument"]
    AI --> CO2D["CO2GasDetector"]
    CO2D --> CCO2D["ContinuousCO2GasDetector"]

    AI -->|calibration| C["Calibration"]
    PHI -->|calibration| PHC["PHCalibration"]
    PHC --> DYEC["DyeCalibration"]
    CRMI -->|calibration| CRMC["CRMCalibration"]
    CO2D -->|calibration| DCO2C["DiscreteCO2Calibration"]
    CCO2D -->|calibration| CCO2C["ContinuousCO2Calibration"]

    style AI fill:#e0e8f0
    style PHI fill:#d0d8e0
    style CRMI fill:#d0d8e0
    style CO2D fill:#d0d8e0
    style CCO2D fill:#d0d8e0
    style C fill:#f0e8d0
    style PHC fill:#f0e8d0
    style DYEC fill:#f0e8d0
    style CRMC fill:#f0e8d0
    style DCO2C fill:#f0e8d0
    style CCO2C fill:#f0e8d0

Which Instrument Each Variable Uses

Variable class Instrument Calibration
DiscretePHVariable PHInstrument DyeCalibration when standard_used is dye, otherwise PHCalibration for TRIS or other standards
DiscreteTAVariable, DiscreteDICVariable CRMInstrument CRMCalibration: certified reference material
DiscreteCO2Variable CO2GasDetector DiscreteCO2Calibration: standard gases
ContinuousCO2Variable ContinuousCO2GasDetector ContinuousCO2Calibration: standard gases
All other measured variables, including continuous pH, TA and DIC AnalyzingInstrument Calibration

Example

A discrete pH variable's analyzing_instrument:

{
  "instrument_type": "spectrophotometer",
  "manufacturer": "Agilent",
  "accuracy": "0.001 pH units",
  "calibration": {
    "technique_description": "Spectrophotometric pH with purified m-cresol purple",
    "calibration_location": "lab",
    "standard_used": "dye",
    "standard_type_and_production": "Purified m-cresol purple, MCR Inc.",
    "dye_purified": true
  }
}