Hello . I have two questions .
1. calculate PTR
PTR = Ipd/Iledx_pk/Rpd/ηled
Code = output of FIFO ; Q=1.15 (when R = 100k) ; PULSE_COUNT = 2 ;
(2)ILED_PK = Icourse*Ifine*Iscale
(3)Rpd=0.26（for blue）;0.42(Ifor IR）
(4)ηled = ηN*K*C
for blue ηN=0.38 ; for IR ηN =0.22
for IR : k=1
for Blue : k=A0+A1*ILED_PK+A2*(ILED_PK)^2+A3* (ILED_PK)^3;
for Blue: C = (Gain*ILED_PK +INTER)/ NORMINAL_SCALAR
Gain= 17*( Gain_COEFF-112)/256-17
INTER = 8*( Int_COEFF-128);
NORMINAL_SCALAR = 17*ILED_PK+622;
So I will calculate Blue PTR as a example .
(a) IPD=Code*Q*(1/PULSE_COUNT)= Code*1.15/2=0.575000*FIFO
(b) Icourse = 50.3+19.8*6; //6 0x23bit[3:0]
Ifine = 0.74+0.022*12; //12 0x25bit[4:0]
Iscale = 0.1+0.9*1; //1 0x23bit13
ILED_PK = Icourse*Ifine*Iscale=169.776398mA
(d) blue ηN=0.38
(e) k=9.8976e-01-5.1448e-03*ILED_PK+2.0287e-05*(ILED_PK)^2-2.9645e-08* (ILED_PK)^3
=0.555975 ( for ILED_PK , I should use mA or A here?)
(f) As I read from efuse register ,for Blue,
Gain= 17*( Gain_COEFF-112)/256-17 = -22;
INTER= 8*( Int_COEFF-128) = 552;
NORMINAL_SCALAR = 17*ILED_PK+622 = 3508.198761; ( for ILED_PK here , I should use mA or A?)
C=(Gain*ILED_PK + INTER)/ NORMINAL_SCALAR= -0.907326
So for Blue PTR = IPD / ILED_PK * (1/Rpd) *( 1 / (ηN*k*C) ) = -0.067954*FIFO
Similarly,for IR, Gain_COEFF=0xC5,Int_COEFF=0xAA, C=0.841255 , So IR PTR = 0.044633*FIFO
Obviously Blue PTR is less than 0 ，It‘s wrong . And I don't know if IR PTR is right or wrong .
If FIFO>1000,Then PTR is over 40 . As I see in the files you provide ,Is it to high?
the max PTR is 4.4
I think I have followed you instruction . Maybe I confused what unit of ILED_PK should be used ?
2. convert PTR to obscuration
As CN0537 says, PTR =γ*β . So I think If I know PTR ,I can calculate β , which is the obscuration level in ft-1.
You say "our device does not measure obscuration per foot. We measure what is essentially the inverse of obscuration per foot"
I dont quite understand it .I think that the higher FIFO is, the PTR is higher . It means the the smoke is thicker .
So the obscuration is higher . Is it wrong ? So If you can expain it to me , or is there any files I missed ？