5BChapter Two: Installation
58BStartup
31
Reporting the Pressure Value
The system pressure can be reported at any time using the appropriate digital communication
commands. The data will be reported as either an INT or REAL value dependent upon device
settings. (e.g. Data Type attribute in the S-Analog Sensor Object)
•
Explicit Request
S-Analog Sensor Object Attribute ID #06 (see page 65) reports the actual, corrected
pressure value from -5 to 110% full scale in the specified units.
•
Polled Request
Assembly Object Instance ID #02 or Instance #05 report the device exception status as
well as the corrected pressure value as either a REAL or scaled INT value, respectively.
See Assembly Object, page 58.
Suggested Pressures for Reading and Control
Table 12 lists the lowest suggested pressures for reading and control with the DMA transducer.
Table 12: Lowest Suggested Pressures for Reading and Control
Full Scale Range
(Torr)
Lowest Suggested Pressure
for Reading (Torr)
Lowest Suggested Pressure
for Control (Torr)
0.1
5 x 10
-5
5 x 10
-4
1
5 x 10
-4
5 x 10
-3
10
5 x 10
-3
5 x 10
-2
100
5 x 10
-2
5 x 10
-1
1000
5 x 10
-1
5 x 10
0
Lowest Suggested Pressures Available for Reading
The pressures listed in the middle column of Table 12 reflect reliable and practical pressures for
different range transducers. Lower readings may be obtained in environments that have stable
temperature and air flow. Temperature controlled transducers can obtain repeatable pressure
measurements down to 1 x 10
-5
Torr.
Lowest Suggested Pressures to Use for Control with Analog Output
The pressures listed in the last column of Table 12 are for reference and represent the pressure
reading of the transducer at 50 mV signal output. A DC signal of at least 50 mV is the
recommended minimum signal level to use when integrating any transducer into complex
processing systems.
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