The Reference / Measurement Cycle; Figure 6-2. Reference / Measurement Gas Cycle - Teledyne T400 User Manual

6.1.3 T R
HE EFERENCE
In order to solve the Beer-Lambert equation (see Section 6.1.1), it is necessary to know
the intensity of the light passing through the absorption path both when O
when it is not. The Model T400 accomplishes this by alternately sending the sample gas
directly to the absorption tube and passing it through a chemical scrubber that removes
any O present.
3
SAMPLE
GAS INLET
SPAN GAS
INLET
ZERO AIR
INLET
DRY AIR
INLET
EXHAUST
GAS
OUTLET
PUMP
The Measurement / Reference Cycle encompasses the following states and ~durations:
142
/ M
EASUREMENT
Particulate
O
3
Filter
Flow / Pressure
Sensor PCA
Sample Gas
Flow Control
O
3
SENSOR

Figure 6-2. Reference / Measurement Gas Cycle

0 seconds Measure/Reference Valve Opens to the Measure Path.
Wait Period. Ensures that the Absorption tube has been adequately
0 – 2 seconds
flushed of any previously present gasses.
Analyzer measures the average UV light intensity of O
2 – 3 seconds
Sample Gas (I) during this period.
3 seconds Measure/Reference Valve Opens to the Reference Path.
Wait Period. Ensures that the Absorption tube has been adequately
3 – 5 seconds
flushed of O
Analyzer measures the average UV light intensity of non-O
5 – 6 seconds
Sample Gas (I
CYCLE REPEATs EVERY 6 SECONDS
Teledyne API – Model T400 O
C
YCLE
Reference Path
Scrubber
Measure Path
SAMPLE
PRESSURE
SENSOR
FLOW
bearing gas.
3
) during this period.
0
Analyzer
3
is present and
3
Measure/
Reference
Valve
-bearing
3
-bearing
3
083730400A DCN8130