Section 1. Overview of the 7200-101 Flow Module
Flow LED is lit, pressing the Menu button once will toggle the display to the Set
Flow function, and the Set Flow LED will be illuminated. The flow rate can then
be set using the Adjust knob.
The control panel functions are as described below:
Measured Flow – The display will show the current flow rate, in mass flow units
of Standard Liters Per Minute (SLPM).
Set Flow – Allows you to set the desired flow rate, in SLPM, or in an uncontrolled
constant blower drive mode, given as a percentage of the total flow capacity. Flow
rates are adjustable between approximately 10-18 SLPM, in 0.1 liter increments. Use
the Adjust knob to change the desired flow rate. If you turn the Adjust knob past
18.0 SLPM, the display will change to show a “C” (Constant), and the displayed set-
ting is constant blower motor drive in % air flow. During normal operation with
the LI-7200/RS, a flow setting of about 15.0 SLPM is adequate for most meas-
urement protocols, including eddy covariance measurements.
Pressure Drop (kPa) – This is an indicator of the blower pressure, which indicates
loss due to tubing, filters, and the LI-7200/RS sensor head (or any other obstruc-
tions). The range is from 0-4.5 kPa, with a normal reading of about 1.0 kPa. If the
air filter becomes clogged, this number will increase, which is a useful diagnostic
indicator for cleaning the filter.
NOTE: On initial startup, you might want to record the Pressure Drop and
Motor Drive (%) readings to establish a baseline of normal unobstructed read-
ings.
Motor Drive (%) – Displays the Pulse Width Modulation (PWM) drive input to
the blower motor as a percentage. During normal operation, the blower motor will
operate at about 25% drive. As with the Pressure Drop above, if the air filter
becomes clogged, this number will increase. This is a useful diagnostic indicator
for cleaning the filter. As the filter becomes clogged (or the air hose is kinked), the
flow rate controls will increase the PWM drive to the blower motor to maintain the
desired flow rate. This, in turn, will require more power.
Address – Displays the accessory bus address, between 32-255. This is primarily
used for future expansion possibilities, where multiple instruments may be con-
nected via the Accessory port. When using the LI-7200/RS Windows application
software to control the Flow Module, this address must match the address chosen
1-8 7200-101 Flow Module
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