Chapter 3
8
Flow can be displayed in units of standard liters per minute
(Std L/min
*
) or in volumetric units of liters per minute (L/min). Refer to
Appendix B
for a description between the two measurements.
Selecting between the two measurements is accomplished through
the serial port. Refer to the RS232 Serial Command Set manual for
instructions on how to select between flow units.
Temperature Measurement
The Models 4040/4043/4045 have an independent temperature
transducer in the flow tube to measure the gas temperature. The
temperature sensor is used for temperature compensation of flow rate
and for converting flow from standard to volumetric units.
Temperature is displayed on the LCD and is available through the
RS232 serial port in the units of degrees Celsius (°C).
Note
: At low flow rates, the temperature inside of the flow tube will
increase because of the heat generated by the thermal flow
sensor. This effect is normal and the temperature of the
incoming gas will be measured once flow resumes.
Pressure Measurement
The Models 4040/4043/4045 measure absolute pressure near the
outlet of the flowmeter in the SI units of kilo-Pascals (kPa). Pressure
measurements are required when converting from standard to
volumetric flow. Absolute pressure measurements are displayed on
the LCD display and are available through the RS232 serial port.
Volume Measurement
The Models 4040/4043/4045 measure total volume by integrating flow
over time. This is a calculated measurement performed by the
flowmeter and is only available using the RS232 serial port. Volume is
not displayed on the LCD display. Refer to the Models
4040/4043/4045 RS232 Serial Command Set manual for instructions
on using the volume function.
*
TSI instruments defines standard conditions as 21.1°C (70° F) and 101.3 kPa (14.7
psia, 1 bar).
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