OB1203 Certification Preparation, Setup, and Test Procedure
X0119984 Rev.1.0
Mar 11, 2021
Page 17
d. Adjust the R-curve: Set the SpO2 value to each of the values in the Excel spreadsheet (see the following
figure and
Recalculation of R-curve
XLS located on the
webpage). This will
automatically adjust the Red AC to simulate the set value in the GUI.
Document the readings in the Excel spreadsheet.
The R-curve is a second degree function of the R value. It uses three coefficients, a factor for R
2
, one for R, and
a constant. The default coefficients in the software are listed at the top of the spreadsheet: -28.149 is the factor
for R
2
, -10.293 for R, and 107.36 is the constant. The numbers for corrected R-curve are shown in green.
Adjustment of the R-curve in the software: Write the new numbers in
SpO2.h
as shown below; re-compile the
program, and re-load it on the MCU.
// R - curve: SpO2 = Rsquare * R * R + Rlinear * R + Rconstant
#define Rsquare -28.149
// coefficient for R square
#define Rlinear -10.293
// coefficient for R
#define Rconstant 107.36
// constant
7.4
Sp02 Saturation Validation
Repeat the measurements as shown in the Excel spreadsheet’s validation step to validate that the DUT is now
measuring correctly.
7.5
Test Report Generation
With the values from the validation step, the “Report” tap generates a test report.
8. Human Calibration Test
This test is performed in an outside test lab. For calibration, typically five subjects are tested. Based on passing
the previous test, we expect to get data from all five subjects. The result we get is a table for each subject of 24
paired reference and DUT readings. Note that these values are derived from 30-second periods where the SpO2
of the test subject is stabilized. This is difficult to do so the exact reference values do not repeat subject to
subject. The result is a “cloud” of data over all of the readings of the reference device and the DUT.
1 Default starting point
Default R-curve as set in the GUI
SpO2 (DUT) used =
-28.149 R^2 +
-10.293 R +
107.36
2 Run the test procedure - enter measured SP02 values in the yellow field
Obtain the new DUT R-curve
Preset
Measured
Calculated
SpO2 WhaleTeq SpO2 DUT
R DUT
100
98
0.42210
Measured SP02 values
95
94
0.52994
90
87
0.68707
85
83
0.76523
80
78
0.85469
75
74
0.92105
68
65
1.057442
3 Use new R-Curve values before running the validation test
Type in the reference and measured SpO2 values SpO2 (DUT) new =
-25.326 R^2 +
-13.432 R +
110.01
New R-Curve Values
