Thermimage (version 2.1)

raw2temp: Converts raw thermal data into temperature (oC)

Description

Converts a raw value obtained from binary thermal image video file into estimated temperature using standard equations used in infrared thermography.

Usage

raw2temp(raw, E = 1, OD = 1, RTemp = 20, ATemp = RTemp, IRWTemp = RTemp, IRT = 1,
RH = 50, PR1 = 21106.77, PB = 1501, PF = 1, PO = -7340, PR2 = 0.012545258)

Arguments

raw

A/D bit signal from FLIR file. FLIR .seq files and .fcf files store data in a 16-bit encoded value. This means it can range from 0 up to 65535. This is referred to as the raw value. The raw value is actually what the sensor detects which is related to t

E

Emissivity - default 1, should be ~0.95 to 0.97 depending on object of interest. Determined by user.

OD

Object distance from thermal camera in metres

RTemp

Apparent reflected temperature (oC) of the enrivonment impinging on the object of interest - one value from FLIR file (oC), default 20C.

ATemp

Atmospheric temperature (oC) for infrared tranmission loss - one value from FLIR file (oC) - default value is set to be equal to the reflected temperature. Transmission loss is a function of absolute humidity in the air.

IRWTemp

Infrared Window Temperature (oC). Default is set to be equivalent to reflected temp (oC).

IRT

Infrared Window transmission - default is set to 1.0. Likely ~0.95-0.97. Should be empirically determined. Germanium windows with anti-reflective coating typically have IRTs ~0.95-0.97.

RH

Relative humidity expressed as percent. Default value is 50.

PR1

PlanckR1 - a calibration constant for FLIR cameras

PB

PlanckB - a calibration constant for FLIR cameras

PF

PlanckF - a calibration constant for FLIR cameras

PO

PlanckO - a calibration constant for FLIR cameras

PR2

PlanckR2 - a calibration constant for FLIR cameras

Value

• Returns numeric value in oC. Can handle vector or matrix objects

Warning

Raw values need to be greater than Planck0 constant

Details

Note: PR1, PR2, PB, PF, and PO are specific to each camera and result from the calibration at factory of the camera's Raw data signal recording from a blackbody radiation source. Sample calibration constants for three different cameras (FLIR SC660 with 24x18 degree lens, FLIR T300 with 25x19 degree lens, FLIR T300 with 2xtelephoto.

Calibration Constants by cameras: SC660, T300(25o), T300(25o with telephoto) lccc{ Constant FLIR SC660 FLIR T300 FLIR T300(t) PR1: 21106.77 14364.633 14906.216 PB: 1501 1385.4 1396.5 PF: 1 1 1 PO: -7340 -5753 -7261 PR2: 0.012545258 0.010603162 0.010956882 }

PR1: PlanckR1 calibration constant PB: PlanckB calibration constant PF: PlanckF calibration constant PO: PlanckO calibration constant PR2: PlanckR2 calibration constant

The calibration constants allow for the raw digital signal conversion to and from the predicted radiance of a blackbody, using the standard equation:

temperature<-PB/log(PR1/(PR2*(raw+PO))+PF)-273.15

Also used in calculations for transmission loss are the following constants:

ATA1: Atmospheric Trans Alpha 1 0.006569

ATA2: Atmospheric Trans Alpha 2 0.012620

ATB1: Atmospheric Trans Beta 1 -0.002276

ATB2: Atmospheric Trans Beta 2 -0.006670

ATX: Atmospheric Trans X 1.900000

References

1. http://130.15.24.88/exiftool/forum/index.php/topic,4898.60.html

2. Minkina, W. and Dudzik, S. 2009. Infrared Thermography: Errors and Uncertainties. Wiley Press, 192 pp.

See Also

temp2raw,

Examples

# General Usage:
# raw2temp(raw,E,OD,RTemp,ATemp,IRWTemp,IRT,RH,PR1,PB,PF,PO,PR2)
###
# Example with all settings at default/blackbody levels:
raw2temp(18109,1,0,20,20,20,1,50,PR1=21106.77,PB=1501,PF=1,PO=-7340,PR2=0.012545258)

# Example with emissivity=0.95, distance=1m, window transmission=0.96, all temperatures=20C, 
# 50 RH:

raw2temp(18109,0.95,1,20,20,20,0.96,50) 
# Note: default calibration constants for the FLIR camera will be used if you leave out the
# calibration data

# Vector example
r<-17000:25000
t1.0<-raw2temp(r,1,0,20,20,20,0.96,50)
t0.9<-raw2temp(r,0.9,0,20,20,20,0.96,50)

dev.off()
plot(r,t1.0,type="l",col="red")
lines(r,t0.9,col="black")
legend("topleft", bty = "n", c("E=1.0", "E=0.9"), lty=c(1,1), col=c("red", "black"))