Emerson Rosemount 935, Reference Manual

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2.3.3 Microprocessor based
The built-in microprocessor analyzes the incoming signals.
A sophisticated mathematical algorithm calculates between the various functions of the
detected signal thresholds. Statistics, ratio algorithms, data communications, diagnostics,
and other functions are performed.
2.3.4 Gas sensitivity
The Rosemount 935 model uses wavelengths around 2.3 µm spectral band to measure air
flammability potential between the source and the detector.
At this wavelength, many hydrocarbon gases have an absorption peak.
This device can also detect other gases, based on cross-sensitivity. Please consult Emerson
for information on how to detect other gases.
2.3.5 Gas calibration
The detector has three calibrations that can be changed by function setup:
• Gas 1: 100 percent methane
• Gas 2: 100 percent propane
• Gas 3: 100 percent ethylene
The full scale of methane and propane is 5 LEL.m.
The full scale of ethylene is 8 LEL.m.
2.3.6 Flash source
The Rosemount 935 transmitter employs the latest generation of Xenon flash bulbs to
provide extended installation distance and maximum reliability.
2.3.7 Heated optics
The Rosemount 935 includes heated optics for the detector and source.
The heater increases the temperature of the optical surface by 5 to 8 °F (3 to 5 °C) above
the ambient temperature to improve performance in icing, condensation, and snow
conditions. Emerson has configured the heated optics to automatically operate when the
change in temperature requires heating (default).
However, you can also define the heated optics as one of the following modes:
1. Not operated (not an option source unit)
2. On continuously
3. Automatic, per temperature change (default)
When operated in Automatic mode, you can define the start temperature below which the
window will be heated (default 41 °F (5 °C)). You can define this temperature between
Reference Manual Technical description
00809-0100-4035 May 2022
Rosemount 935 11