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Model 9110T NOx Analyzer Setup Menu
Teledyne Analytical Instruments 96
5.4. SETUP RNGE: ANALOG OUTPUT REPORTING RANGE
CONFIGURATION
Use the SETUP>RNGE menu to configure output reporting ranges, including scaled reporting ranges to
handle data resolution challenges. This section describes configuration for Single, Dual, and Auto Range
modes.
5.4.1. 9110T PHYSICAL RANGES
The 9110T NO
x
analyzer measures NO
x
, NO and NO
2
concentrations from 2 to 20,000 ppb.
Electronically the 9110T analyzer converts the 0-5 volt analog signal output by the PMT into a digital
signal with 4096 counts of resolution. Since its measurement range is 0 ppb to 20,000 ppb, this only
allows about 3 ppb per count. While this might be acceptable for high concentration measurements
made in parts per million units (ppm), it is not good enough for lower level NO
x
measurements. To
overcome this limitation the 9110T is designed with two physical measurement ranges:
A LOW range that measures concentration from 0 ppb to 2,000 ppb with a resolution of 0.27 ppb per
count.
A HIGH range that measures the full 20,000 ppb range of the analyzer.
The analyzer’s CPU chooses the appropriate range based on how the user sets up the reporting ranges for
the instruments analog outputs when an analog range is selected with a lower limit between 0 and 2000
ppb the analyzer will utilize its low physical range. When an analog range is in use that has a reporting
range with an upper limit set between 2001 and 20,000 ppb the instrument will operate in its high
physical range.
Once both ranges have been using the same span gas values the analyzer’s front panel will accurately
report concentrations between 0 and 20,000 ppb, seamlessly switching between the low and high
physical ranges regardless of the selected analog reporting range.
5.4.2. 9110T ANALOG OUTPUT REPORTING RANGES
For applications using chart recorders or other analog recording devices, the 9110T's 20,000 ppb
physical range can cause resolution problems. For example, in an application where the expected
concentrations of NO, NO
2
and NO
x
are typically less than 500 ppb, the full scale of expected values is
only 2.5% of the instrument’s 20,000 ppb physical range. The corresponding output signal would then
only be recorded across 2.5% of the range of the recording device.
The 9110T solves this problem by allowing the user to select a reporting range for the analog outputs
that only includes that portion of the physical range that covers the specific application. This increases
the reliability and accuracy of the analyzer by avoiding additional gain-amplification circuitry.
Note Only the reporting range of the analog outputs is scaled.
Both the DAS values stored in the CPU’s memory and the concentration
values reported on the front panel are unaffected by the settings chosen
for the reporting range(s) of the instrument.