EXP-19 Radiometry and Photometry

Topics

Black Body Radiator
Thermal Light
Cold Light
Sensitivity of Human Eye
Photometric Units
Calibrated Lamp
Lock-In Amplifier
Lamp Calibration
1/r2 Law


Principle of operation

The heart of the set-up, besides the lock-in amplifier (F), is the standard lamp model WI40/G (A) calibrate in units of luminous intensity. The photo detector (D) has a wavelength independent sensitivity covering the spectral range of 0.2 - 20 µm and is calibrated in radiometric units. In order to prevent unwanted ambient light to pass to the detector a shield (B) with adjustable iris is used. The solid angle of the light bundle for the measurement is defined by the adjustable diameter of the iris. An almost complete suppression of ambient light is achieved by using the so called lock-in technique. For this purpose the light chopper (C) modulates the light bundle to be measured with a defined frequency, which is determined by the revolution speed and the number of sectors of the chopper blade. The lock-in amplifier receives its gating signal from the controller (CHS) in such a way that a measurement is taken only when the chopper blade is opened, thus obtaining a high degree of suppression of ambient light.

 
 


Required Equipment

Cat. No.    Qty.    Description
02.1000     1       Profile Rail, 1000 mm
05.0104     1       Calibrated Tungsten lamp 30V/6A ,incl. socket and rod mounts
07.0004     1       BNC connection lead, 1.5 m, set of 4
07.0238     1       Stabilised power supply 30V/6A
09.0194     1       Iris diaphragm, rod mounts
09.0196     1       Light chopper
09.0197     1       Thermoelectric detector, 100 nm - 40 µm linear, calibrated, preamplifier
10.0190     1       EXP 19 manual
19.0130     1       Dual phase lock-in amplifier
Required Options:
19.0396     1       Digital multimeter 31/2 Digits
19.0451     1       Digital multimeter 4 Digits
Options:         
09.0199     1       Set of spare parts