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Optical Methane Detector

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The Optical Methane Detector (OMD™), is the first of the “next generation” leak detection systems which address the high cost presently associated with leak surveying. This new technology combines sensitivity, selectivity and speed through the combined use of optics and electronics. The OMD is mounted on the front of a survey vehicle and detects the presence of methane in air. It provides for the detection of gas leaks down to 1 part per million (PPM). It has no moving parts that will prevent the instrument from operating. It requires no support gases and is virtually maintenance free.

The OMD is mounted on the front of a survey vehicle. It employs an infrared (IR) light beam across the front of the vehicle

Based on the absorption of infrared (IR) radiation by methane, the OMD consists of an IR light source directed at an IR optical detector. These two are spaced approx. four feet apart across the width of the vehicle. An optical filter in front of the detector transmits primarily methane specific IR wavelengths from the light source. In the absence of methane, these wavelengths are unaffected and produce a steady output signal from the detector. When the vehicle passes through a plume of natural gas, methane in the plume will absorb some of the IR light reaching the detector. As a result there is a sudden decrease in IR light at the detector causing a decrease in detector output. This change in detector output is transmitted to the display panel located next to the vehicle’s driver and becomes a signal, both audio and visual. Gas concentration is calculated in the OMD by converting the methane to light ratio to PPM.

The data is displayed in both analogue and digital form. The analogue display appears as a peak scrolling across the display screen. The OMD will also detect other hydrocarbons such as ethane and propane but with less than half the sensitivity.

The OMD operates reliably under a variety of environmental conditions including dry weather, snow, ice and temperatures from -22° F to +122° F. Its sensitivity, calibration or response is not affected by small fluctuations in the light beam or by reasonable amounts of dust, or snow on the optics. An internal calibration test cell is included so the operator can verify proper operation from the vehicle cab at any time before, during or after a leak survey. An Installation Mounting Kit is available for mounting the OMD to the front of a vehicle. All interconnecting cabling is provided with the OMD including the cable to obtain power to operate the instrument from the survey vehicle 12 volt battery. An RS232 port is included whereby a personal computer may be connected to acquire and save the survey data with the appropriate software.

SPECIFICATIONS
Configuration: Double - ended
Sensitivity: 1 PPM / meter CH4
Measurement Range: 1 to 200 PPM
Accuracy: ± 10% (1 to 100 PPM range) ± 20% (100 to 200 PPM range)
Above 200 PPM = Not relatively accurate
Display Ranges: 10, 30 and 90 PPM

Self - test: During boot – up
Calibration/Test: Via operator, self - contained
Calibration: Via RS-232 through software
Base - Line Compensation: Via RS-232 through software
Display: Back-lit 2" x 6" graphics LCD, adjustable contrast
Operator Interface: Sealed membrane switch overlay

Operator Alarms:
Signal: High pitch audible with adjustable set point, pitch increases with concentration.
Adjustable volume.
Error: Low pitch audible with adjustable set point
Error alarms provided for: Warm-up, Low Light,
Communication Failure & Battery low

System Power: 72 Watts @ 12 VDC
System Voltage: 12 - 16 VDC
System Weight:
External Sub - Systems: 17 pounds
Power Box 6 pounds
Internal Display 3 pounds
Cables 4 pounds

Crossbar Assembly Length: 63.25, 32, 51.25in. ± 2in.
Mechanical Mounting: Strut bracket mount
Installation Time: 2 hours, typical
External Housing Rating: NEMA 3S and IP 54
Display Housing Rating: Spill proof
System Materials: Aluminum and plastic
Environmental PCB Control: Conformal PCB coating
Operating Temperature Range: - 22°F to 122°F
Operating Humidity Range: 5 to 100 % RH, non-condensing

Ordering Information:
2500100 - OMD, Complete, 32” Crossbar (plus 6”)
2500300 - OMD, Complete, 51” Crossbar (plus 6”)
2500400 - OMD, Complete, 63” Crossbar (plus 6”)
100132-0 - OMD Display Mount