The EXM500 is an extractive online gas analyser dedicated to Continuous Emission Monitoring.
This new model is based on a 2048 pixels CCD (charge-coupled device) giving a higher resolution (0.1 nm) and a longer lamp life time (3 years) It is based on UV spectroscopy that brings a higher sensitivity than infra-red and gives the possibility to measure several gases simultaneously. A high selectivity is achieved by a fast Fourier transform (FFT) on the absorbance spectrum for all the gases having a periodic structure like NH3, SO2, NO and others. All the internal gas circuit is heated at 190°C to admit directly hot and humid combustion gases. The EXM500 is presented in a standard 19″ rack. This model may include a heated sampling pump as an option.
MAIN METHOD : UV SPECTROSCOPY
- Several gases can be measured simultaneously thanks to the UV spectroscopy method by using different wavelengths and algorithms. For gases with a periodic absorption spectrum such as NH3, SO2, NO, CS2 or acetylene, an algorithm based on FFT (Fast Fourier Transform) guarantees a very good selectivity of measurement. The solid-state design due to the UV spectroscopy gives a high reliability of the measuring system with quite no maintenance.
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- The UV lamp is a xenon flash lamp with a high lifetime and without thermal effect that may generate measurement drift.
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- The gas flow cell has two quartz windows to transmit the UV light through the measured gas. The standard path length of the flow cell is 240 mm.
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- The spectrograph is based on a concave grating to minimize the optical parts and the spectrum is read on a 2048 pixel CCD with a resolution of 0.1nm.
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- The spectrograph is based on a concave grating to minimize the optical parts and the spectrum is read on a 2048 pixel CCD with a resolution of 0.1nm.
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- A zero is done automatically on zero air or nitrogen with an adjustable period (if possible every 2 or 4 hours but once per day remains acceptable).
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- The absorbance spectrum is calculated from the reference spectrum acquired during the zero step.
USER-FRIENDLY INTERFACE
A colour touch screen display interface allows the user to easily navigate through a number of screens that are used to set and check all of the operating conditions of the instrument. A protective film limits the risk to damage the surface of the touch screen, especially against solvent and corrosive liquid.
NO INTERFERENCE WITH CO, CO2 AND CH4
The major emission gases like CO, CO2, and CH4 have no UV absorption, therefore they don’t interfere with the measured gases. H2O has a weak absorption in the UV range but at different wavelengths than combustion gases like NH3, NO, NO2 or SO2. Consequently, H2O, with an usual concentration between 5% and 20%, is not disturbing the measurements.
LOW MAINTENANCE AND HIGH RELIABILITY
The design has been specially oriented for low maintenance and high reliability on the measurements. The UV xenon lamp is specified for a lifetime of 109 flashes. Therefore, the lifetime is about 3 year with continuous measurements or 10 years with one measurement per minute. This reduces considerably the maintenance and the risk of wrong measurement due to aged lamps or its replacement.
HEATED VERSION
The analyser is provided with an heating system for the gas circuit. The heating temperature can be adjusted up to 190°C. The high temperature evaporates any deposits on the windows. More…