Vigilantplant TDLS8000, User Manual

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<3. Installation, Wiring, Optical Axis Adjustment, and Piping>
3-2
IM 11Y01D01-01EN
3.1.1 Measurement Point Selection
Take the following process conditions into consideration when selecting the measurement point.
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Process gas flow rate conditions
Set the measurement point to a location where the concentration distribution of the streamline
flow is uniform.
In the case of a duct or flue with a circular cross section, a typical measurement point is where
the distance from the end of a curved process area is at least three times the diameter (D) of the
duct or flue and where there is nothing that would interfere with measurements.
In the case of a duct or flue with a rectangular cross section, the equivalent diameter (D) can be
determined from the following equation.
Diameter (D) = 4 × duct cross sectional area/duct circumference
If such point is not available or if setting a measurement point at such point is not possible, the
measurement point is a location two-thirds of the length away from the duct inlet end or one-third
from the outlet end.
Once the measurement point is determined, double-check that it is at the appropriate location.
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Process gas temperature
Install the TDLS8000 in a location with minimal process gas temperature fluctuations.
If the gas temperature fluctuation where the TDLS8000 is installed exceeds ±10 °C, connect
an external thermometer to the TDLS8000 temperature input terminal and enter the actual
measured gas temperature to obtain correct measurements (for details, see “6.1.3 Process
Temperature”).
Check that a thermometer suitable for the maximum process gas temperature is being used.
In general, the lower the gas temperature, the better the measurement.
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Process gas pressure
Install the TDLS8000 in a location with minimal pressure fluctuations.
If the gas pressure fluctuation where the TDLS8000 is installed exceeds ±5 kPa, enter
the pressure signal from a separately applied process pressure meter to obtain correct
measurements (for details, see “6.1.2 Process Pressure”).
Check that a pressure meter suitable for the maximum process gas pressure is being used.
Check that the process window interfacing the process gas is suitable for the maximum preset
gas pressure.
In general, the lower the gas pressure, the better the measurement.
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Process dust/particulate concentration
Install the TDLS8000 in a location with minimal dust concentration.
The transmission of the measurement laser beam will decrease due to dust or particles.
Measurement will not be affected as long as the transmission loss is within limits, but if it exceeds
limits, an alarm will occur. The dust load also depends on the process optical path length. For
details, contact your nearest Yokogawa representative.
In addition, install the TDLS8000 in the location such as not causing breakage of the process
window and LAO unit lens by foreign object might damage the window and lens in process gas.
3rd Edition: Jun. 10, 2016-00