Ultima OPIR-5 Detector
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2.0 Product Description
2.1 General Description
The Ultima OPIR-5 Detector is a hydrocarbon gas detector (Figure 1). The system
consists of a Source and a Receiver. Both units are calibrated at the factory and
need no further alignment. The operation of the Ultima OPIR-5 Detector can be
checked by placing a Test Gas Film in front of the Receiver. The system requires
only a periodic cleaning of the windows to assure dependable performance,
and is
recommended prior to zero check, test gas, and optical integrity testing. The Ultima
OPIR-5 Detector continuously monitors hydrocarbon gases. The gas detection
range of a Receiver calibrated for methane is 0 to 5,000 ppm•meter and 0 to 5
LEL•meter while that for propane it is 0 to 2,000 ppm•meter and 0 to 1 LEL•meter.
The Receiver provides two 4 to 20 mA analog signals, one proportional to
ppm•meter and the other to LEL•meter. Alarm and Fault relays, split range (A/O-
ppm), Modbus, and HART outputs are optional.
The Ultima OPIR-5 Detector is easily aligned using the digital display and
adjustable mounting arms, therefore does not require any bulky setup equipment
such as digital volt meters and handheld alignment aids. For setups that require the
distance from the Source to the Receiver to be greater than 100 meters, MSA
offers an optical alignment scope that makes the initial alignment easier.
2.1.1 Infrared Detection Principles
Most gases absorb infrared radiation. Hydrocarbon gases absorb infrared radiation
at specific wavelengths but with different degrees of absorption. Absorption of the
radiation follows the Beer-Lambert Law, which states that the transmittance (T) of
radiation through an absorbing medium decreases exponentially by the product of
the absorption coefficient (A), the concentration (C), and the path length (L):
T = exp(-ACL)
Here T
0
is the transmittance of light containing no absorbing medium.
2.1.2 Ultima OPIR-5 Detection Method
The Ultima OPIR-5 Detector uses a single beam, dual wavelength method of
infrared absorption detection. The gas absorbs one wavelength but not the other,
which is the reference wavelength. By comparing the signals from these two
wavelengths, the detector measures gas concentration. The reference wavelength
is chosen to compensate for interferences that can otherwise occur from
atmospheric variation, such as humidity, rain, dust, snow, fog, steam, and
temperature. This method of detection comes under what is commonly known as
the non-dispersive infrared (NDIR) absorption principle.
NOTE:
Extremely dense fog, steam or interruption of the beam by an object or
person may cause a system fault
2.1.3 Measurement
Scale
With the Ultima OPIR-5 Detector, as there is no fixed path length, the reading is
reported in concentration meter. The Ultima OPIR-5 Detector reports
