User's Manual Part 3
10-19
be sure to use a Masimo T-adapter that samples the gas from the center of the T-adapter
(see below). See section
12
for ordering details.
Flow control
During normal operation, a sidestream gas analyzer is continuously fed with a small
sample gas flow. To pull the gas through the sampling line and maintain a steady flo w, a
high-precision flow control system is required. In !SA sidestream gas analyzers, the flow
control system consists of an integrated micro pump, a zero valve and a flow controller.
The pump is fitted with a low-power brushless motor incorporating three miniature ball
bearings to ensure trouble free operation without the need for regular maintenance. Its
balanced shaft design and integrated pneumatic filter virtually eliminates pressure and flow
variations.
System response
In any sidestream gas analyzer, there are three major time parameters characterizing the
system:
•
Total system response time
•
Delay time
•
Rise time
When designing a sidestream gas monitoring system, the physical characterist ics of
several components have to be considered. Parameters such as sampling line volume,
tubing material and the physical design of the sampling interfaces play decisive roles in
determining the responsiveness of the system.
Generally, the total system response time equals the delay time plus the rise time.
The rise time is defined as the time required for a step function change at the sampling
site to bring about a rise from 10% to 90% of the final gas concentration value. The total
numbers of gas fittings together with the physical design of the fittings are examples that
effects the rise time. Fast rise times are important when monitoring infants with high
breathing rates.
The delay time is defined as the time required for a step function change at the sampling
site to result in 10% of the final value. Parameters affecting the delay time are the sample
flow rate, tubing length and tubing inner diameter. In mainstream gas monitoring, where
no tubing exist, the delay time is virtually zero, whereas a sidestream system has a
sample delay time of a few seconds.
Leak test
1.
Connect a Nomoline Adapter and a Nomoline Extension sampling line or equivalent to
the ISA gas analyzer, with the analyzer connected to Masimo Gas Master.
2.
Tightly block the gas inlet of the Nomoline sampling line.
Check the field "Atm press - cuvette press [kPa]" in Masimo Gas Master - the
pressure value will start to rapidly increase, until the internal pump stops.
When the internal pump stops and while keeping the inlet blocked, quickly block the
exhaust port tightly. When blocked, the "Atm press - cuvette press [kPa]" in Masimo
Gas Master shall be >6 kPa.
3.
Stop the pump by sending parameter "Stop pump" under "Installation & maintenance"