Teledyne Camera Accessories T100 사용자 설명서

concentrations of some or all of these may be very high, specific steps MUST be taken 
to remove them from the sample gas before it enters the analyzer. 

13.1.9.5. LIGHT POLLUTION 

Because T100 measures light as a means of calculating the amount of SO

2

 present, 

obviously stray light can be a significant interfering factor. The T100 removes this 
interference source in several ways.  

  The sample chamber is designed to be completely light tight to light from sources 

other than the excitation UV source lamp.  

  All pneumatic tubing leading into the sample chamber is completely opaque in order 

to prevent light from being piped into the chamber by the tubing walls. 

  The optical filters discussed in Section 13.1.7; remove UV with wavelengths 

extraneous to the excitation and decay of SO

2

/SO

2

*. 

  Most importantly, during instrument calibration the difference between the value of 

the most recently recorded PMT offset (refer to Section 13.1.6) and the PMT output 
while measuring zero gas (calibration gas devoid of SO

2

) is recorded as the test 

function OFFSET.  This OFFSET value is used during the calculation of the SO

2

 

concentration.  

Since this offset is assumed to be due to stray light present in the sample chamber is also 
multiplied by the SLOPE and recorded as the function STR. LGT.  Both OFFSET 
& STR. LGT are viewable via the front panel (refer to Section 4.1.1). 

The O

2 

sensor applies paramagnetics to determine the concentration of oxygen in a 

sample gas drawn through the instrument. 

The oxygen sensor used in the T100 utilizes the fact that oxygen is attracted into strong 
magnetic field while most other gases are not, to obtain fast, accurate oxygen 
measurements.   

The sensor’s core is made up of two nitrogen filled glass spheres, which are mounted on 
a rotating suspension within a magnetic field (refer to Figure 13-7).  A mirror is 
mounted centrally on the suspension and light is shone onto the mirror that reflects the 
light onto a pair of photocells.  The signal generated by the photocells is passed to a 
feedback loop, which outputs a current to a wire winding (in effect, a small DC electric 
motor) mounted on the suspended mirror. 

Oxygen from the sample stream is attracted into the magnetic field displacing the 
nitrogen filled spheres and causing the suspended mirror to rotate.  Therefore, the 
amount of light reflected onto the photocells and therefore the output levels of the 
photocells.  The feedback loop increases the amount of current fed into the winding in 
order to move the mirror back into its original position.  The more O

2

 present, the more 

the mirror moves and the more current is fed into the winding by the feedback control 
loop. 

A sensor measures the amount of current generated by the feedback control loop which 
is directly proportional to the concentration of oxygen within the sample gas mixture. 

06807C DCN6650