Fluke Biomedical 2MF Index - Manual (Page 79)

Manufacturers Mode
Mathematical Background
11
11-3
The the Simulator calculates the R-value (as far as the oximeter is concerned) with this
formula:
(0<=ac <=255) (0<=rdc <=4095) REDUUT
255
* *
4095
(0<=rdc <=4095) REDUUT
4095
(0<=rac <=4095)
4095
esl140.eps
__________________________________________________________________
(0<=ac <=255)
255
(0<=irac <=4095)
4095
(0<=irdc <=4095) IREDUUT
4095
(0<=irdc <=4095) IREDUUT
4095
* *
esl141.eps
Notes on the Formulas
The ac term above attenuates both red and infrared pleth waves identically, to control
simulated pleth strength. The default value is 255. In addition, red-light dc (rdc) and
infrared light dc (irdc) modulate REDUUT and IREDUUT, which are transmissivity
numbers. Zero would mean that no UUT (Unit Under Test) pulse would be allowed to
pass through the Simulator. Attenuation would be 4,095 minus the value set. The default
value here is 1,000.
Red-light ac (rac) and infrared light ac (irac) are true attenuations. A value of 1,000, for
example, means that the pleth wave will attenuate the UUT pulse by approximately 25%
of the maximum pleth amplitude. The default value for irac is 1,000. Values for rac
range from 400 to 4,000, corresponding to .400 to 4.000 R-values; this covers the
required range.
By having the pleth attenuation operate on the dc attenuated UUT flash, the Simulator
becomes immune to fluctuations in oximeter flash amplitude, which can vary
considerably.
Note
To reduce the corresponding dc term only, you increase the pleth amplitude
term; conversely, to increase only the pleth amplitude term, you reduce the
corresponding dc term. Keep this in mind when setting up performance
limits tests.
The R-Value Equation
By dropping out terms that equate to one, and by accounting for the dc terms being
transmissivities, we can reduce the previous equation to this:
R =
rac / (4095 - rdc)
irac / (4095 - irdc)
esl142.eps