3 | Model 7300A | |
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These lamps are typically rated for 20,000 hours continuous operation when run in the DC mode (+5VDC). This collimated energy is directed through parallel infrared beams. The radiant energy passes through tubes containing a continuously flowing sample gas. As the beam passes through the reference tube, the energy of the beam is unattenuated and balanced which provides a standard of source energy output for comparison. The gas of interest is present in the measurement tube, however, the energy of the beam will be attenuated at the specific absorption wavelength.
After passing through the two tubes, the radiant beams are reflected and imaged by a second concave mirror onto a photon detector. A spectral filter, located just in front of the detector, represents the precise “window” of the absorption band for the specific gas of interest. Energy outside the band is eliminated.
The detector converts the optical energy from the radiant beams into an electrical signal which is modulated in proportion to the gas concentration.
D etector
IR
Source 
Pream p
D ifference
Am plifier
Auto Zero Am plifier
D etector
Pream p
Th erm istor
H eater
Temperature
Control
Fine
Adjustment
M
U
X
Auto-
R ang e
C oarse A djustm ent
A to D
C onverter
D igitial to Analog
C onverter (DAC )
To C PU
C oncentration and R ange
C oncentration and R ange
Alarm 1
Alarm 2
System
Failure
Alarm
R S
C e n tra l
P ro c e s s in g
U n it
(C P U )
D isplaysProcessing
Pow er |
| A to D C onv |
Supply |
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R ange
C ontacts (4)
External
Valve
C ontrol
R em ote Span C ontrol
R em ote Zero C ontrol
C al
C ontact
Block Diagram of the Model 7300A Electronics
Teledyne Analytical Instruments |
