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NovaStar Data / Calibrations

Introduction

A calibration is used to convert a measured raw value into a scaled value.

Calibrations in NovaStar

A calibration in NovaStar is used to convert a point's raw value into a scaled value that can be used for calculations, display, and decisions. Calibrations are key in the data collection system because they allow raw sensor values to be converted to scaled values with engineering data units that can be used to make decisions. Calibrations have an effective time because sensor characteristics can change over time.

Each NovaStar point can be assigned a calibration that includes:

  • base_value - used to offset the base value to new datum, often used to apply an elevation delta so that data values measured using a device's elevation are reported at a regional or global elevation scale
  • adder - value to add to the raw value
  • multiplier - value to multiply the raw value
  • effective_time - when the calibration should begin to be used, until a new calibration with later effective time is defined

The calculation is as follows:

  scaled_value = base_value + (raw_value + adder)*multiplier

If the sensor is reporting a scaled value or a data import is used, then base_value=0, adder=0 and multiplier=1.0, resulting in no change to values.

Data web services allow calibrations to be queried for analysis and display because it may be helpful to know when calibrations have changed, for example when troubleshooting data issues.

Services

The following are services related to calibrations:

  • calibrations - return calibrations
  • tscatalog - returns a list of time series, including calibration time series
  • ts - returns a time series