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4-16 O
PERATING
G
UIDE
, TEOM 1405
T
HERMO
F
ISHER
S
CIENTIFIC
•
Average pressure
. This field (visible only when passive is selected) contains
the average pressure (atm) setting for passive flow control. The default
setting is 1 atm. To adjust the setpoint, select the button to display the
keypad (Figure 4-3).
The instrument is delivered with the following temperature and pressure
settings:
Standard temperature 25° C
Standard pressure 1 atmosphere (atm)
Average temperature
25° C
Average pressure 1 atmosphere (atm)
The user must choose how they want the monitor to control the volumetric
flow: actively or passively:
• Active Flow Control
uses actual ambient pressure and ambient
temperature from instrument sensors to set the flow rates
• Passive Flow Control
uses operator input ambient temperature and
ambient pressure to control flow. At their discretion, operators can
input seasonal average temperature and pressure.
To select
active
flow control, select the
Active
flow control button (Figure
4-13). To use the actual temperature and pressure to control the volumetric
flow, you must install the ambient temperature/humidity sensor The
instrument’s mass flow controllers measure flow on a mass basis. All of the
size-selective inlets, including the PM-10 inlet, operate on a constant
volumetric flow basis.
If the user chooses to use
passive
flow control, they must select the
Passive
flow control button (Figure 4-13). The average temperature and average
pressure, used by the instrument, may vary with season and altitude. If the
user wants the unit to use the average temperature and pressure to control
the volumetric flow, they should manually adjust the average temperature
and average pressure settings as climatic conditions change. The user
usually has to adjust the average pressure only once for the average
barometric pressure at the sampling site (i.e., station pressure — not
adjusted to sea level). However, the user generally must adjust the average
temperature periodically (often 4 times per year) in accordance with
changing average ambient temperatures.
Содержание TEOM 1405
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