Calibration and Specification Considerations

When Using Modular Instrumentation

Mike Dobbert

Environmental ConditionsOperating SoftwareMulti-module Instruments

Modular Instruments

Configuration FlexibilityInterchangeabilityMeasurement SpeedSize

Traceable Measurements!(calibration required)

Modules have neighbors.

Environmental Conditions

Fixed Configuration.

Ambient environmental conditions are a good predictor of the internal operating conditions.

Environmental Conditions

Environmental Conditions

Calibration Laboratory

Ambient environmental conditions outside the chassis are not necessarily a good indication of the internal operating conditions!

Environmental Conditions

Environmental Conditions

Environmental Conditions

Instrument Drivers (reside outside the module)Installed Drivers at the Calibration Laboratory

Ideally, the same software driver revision is used for both calibration and during intended operation.

Operating Software

Operating Software

Set of modules working together as a single instrument.Instrument accuracy may depend on more than one module.

Multi-Module Instruments

Calibrate the multi-module instrument as a single instrument.Multi-module instruments require a unique identification(when calibrated as a set).

Calibration Manager

Multi-Module Instruments

Multi-Module Instruments

Model multi-module instruments as a function of individual modules.

(GUM method of uncertainty propagation.)

Multi-Module Instruments

Multi-Module Instruments

𝒚=𝒇 ( 𝒙𝟏 , 𝒙𝟐 ,𝒙𝟑 )

Tradeoff: modular flexibility versus accuracy.

In-Situ Calibration

Address environment and controlling software issues.

Conclusion

Environmental Conditions

Module environment highly dependent on system configuration.

Operating Software

Instrument driver resides outside the module.

Multi-module Instruments

Calibration of a set of modules. Calibration of individual modules

utilizing the method of the GUM.