Cell And System Scaling - Mantracourt DSC User Manual

Cell
The 'Cell' calibration converts the mV/V output into a cell-force reading.
This can be used by an OEM sensor manufacturer to provide a standard, calibrated output in force units, which could
be based on either typical or device-specific calibration data.
(This stage also includes the temperature- and linearity-corrections, not covered here)
The outputs from this are
•
CMVV is the temperature compensated mV/V (MVV).
• CRAW is the scaled temperature compensated value CMVV
•
CELL is a load cell force reading in "Force" units (e.g. kN)
• CRAWUR and CRAWOR are two flags indicating under or, over range for the force measurement.
System
The 'System' calibration converts the Cell output into a final output value, in the required engineering units.
This is normally be set up by a systems installer or end user, to provide whatever kind of output is needed,
independently of device-specific information in the Cell calibration.
(Making this split allows in-service replacement without re calibration).
The Outputs From This Are
• SRAW is a re-scaled and offset adjusted output derived from CELL
•
SYS is the final output value, after removing a final user output offset value (SZ) from SRAW
• SRAWUR and SRAWOR are output warning limit flags.
In practice, SRAW and SYS can be used to represent something like gross and net values.

Cell and System Scaling

Both the Cell and System calibrations are simply linear rescaling calculations –i.e. they apply a gain and offset.
In both cases, four parameters define the scaling, offset and min and max limit values. These calculations are
applied in the following way:
Output = (Input × GAI) – OFS
Output = min (output, MAX)
Output = max (output, MIN)
(In addition, if the value exceeds either limit, one of two dedicated error flags is set)
The control parameters thus have the following characteristics: –
• GAI is the multiplying factor, set in "output-units per input-unit"
• OFS is the value that gives zero output, set in "output units"
• MAX and MIN are output limit values, set in "output units"
The units and functions of the main scaling controls can thus be summarised as –
Cell Calibration
CGAI Force/mV/V
COFS Force
CMIN Force
CMAX Force
System Calibration
SGAI Eng/ Force
SOFS Eng
SMIN Eng
SMAX Eng
SZ Eng
(MVV is mV/V, "force" is force units, and "eng" is engineering units)
35 Micron Meters
mV/V gain factor
CELL Offset Value
Minimum value for CRAW
Maximum value for CRAW
SYS/CELL gain factor
SRAW value offset
Minimum value for SRAW
Maximum value for SRAW
SYS value offset
DCell & DSC User Manual