Application Notes >> Technical Notes

Using the Calibration Spreadsheets

Introduction 

There are two calibration spreadsheets included with this package: uncial.xls and bical.xls.  These spreadsheets can be used to calculate the non-linearity and hysteresis of any sensor, but have been written primarily for use with Validyne pressure transducers. 

Unidirectional Calibration

 Unical.xls is for unidirectional calibrations.  A unidirectional calibration is a transducer that is calibrated in from 0 to some positive full-scale pressure.  Unical.xls includes some sample data from a P55D pressure transducer calibrated from 0 to 20 psid, but any Validyne pressure sensor, and any range of pressure units and signal can be substituted.  It is possible to enter pressure units in In H2O, mm Hg, etc and the output signal can be in Vdc, mV/V or mA. 

 There are just two columns of data you need to enter in unical.xls:

 Pressure Input  - Starting at cell B9 continuing to cell B13

 Signal Output – Starting at cell C9 continuing to cell C13

 The column marked BFSL represents the Best-Fit Straight Line value of the data.  The slope and intercept of this best-fit line appear in cells F4 and F5 respectively.  The output sensitivity is given in cell F6. 

 The column marked Error, %FS is the resulting error of the transducer signal as compared to the BFSL value.  The greatest of these is given as Non-Linearity, %FS in cell E18.  The non-linearity at each of the five points in the calibration curve is given in the graph.

 Hysteresis is defined as the greatest difference between upscale and downscale readings at the same pressure.  This is determined as a % of FS by the spreadsheet and is shown in cell E19.

Bidirectional Calibrations

 Bical.xls is for bidirectional calibrations.  A bidirectional calibration is a transducer that is calibrated in from 0 to both positive and negative full-scale pressures.  Biical.xls includes some sample data from a P55D pressure transducer calibrated from 0 to 2 psid, but any Validyne pressure sensor, and any range of pressure units and signal can be substituted.  It is possible to enter pressure units in In H2O, mm Hg, etc and the output signal can be in Vdc, mV/V or mA. 

 There are just two columns of data you need to enter in bical.xls:

 Pressure Input  - Starting at cell B9 continuing to cell B17

 Signal Output – Starting at cell C9 continuing to cell C17

 The column marked BFSL represents the Best-Fit Straight Line value of the data.  The slope and intercept of this best-fit line appear in cells F4 and F5 respectively.  The output sensitivity is given in cell F6. 

 The column marked Error, %FS is the resulting error of the transducer signal as compared to the BFSL value.  The greatest of these is given as Non-Linearity, %FS in cell E18.  The non-linearity at each of the five points in the calibration curve is given in the graph.

 Hysteresis is defined as the greatest difference between upscale and downscale readings at the same pressure.  This is determined as a % of FS by the spreadsheet and is shown in cell E19.

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