Teledyne manual Block Diagram of the Model 7300A Electronics

3 Start-up and Theory of Operation Model 7300A

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

0-1 V dc

C oncentration and R ange

4-20 m A dc

C oncentration and R ange

Alarm 1

Alarm 2

System

Failure

Alarm

R S -232

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

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

3-4 Teledyne Analytical Instruments