Tethys Instruments - Model CEM400 -Online Gas Analyser

• 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, formaldehyde 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.
• The uv lamp is a xenon flash lamp with a high lifetime and without thermal effect that may generate measurement drift.
• The gas flow cell has two quartz windows to transmit the uv light throught the measured gas. The standard path length of the flow cell is 240 mm.
• The spectrograph is based on a concave grating to minimize the optical parts and the spectrum is read on a 254 or 512 pixels diode array.
• 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).
• The absorbance spectrum is calculated from the reference spectrum acquired during the zero step.

The colour touch screen and intuitive interface available in 8 different languages (Chinese, English, French, German, Italian, Portuguese, Spanish, Turkish) makes very easy to test or configure the analyser. Many test functions allows to test and troubleshoot each element of the analysers (light signal, pumps, solenoid valves, etc...) to setup quickly a maintenance diagnostic.

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.

Several gases can be measured in a same analyser if the sample gas composition is compatible with the selected algorithms and wavelengths. The analyser gives high measurement selectivity thanks to the recognition of the specific UV absorption spectrum of gases by using proprietary algorithms.

An internal measurement of temperature and pressure of the sample is performed. A ratio related to the ideal gas law is applied on the measured value to compensate the effects of temperature and pressure.

The CEM400 is an extractive online gas analyser dedicated to Continuous Emission Monitoring. 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 some others. All the internal gas circuit is heated at 190°C to admit directly hot and humid combustion gases. the CEM400 stand in a watertight wall mounted enclosure. This model may include a heated sampling pump as an option.

• Data storage: 5000 measurements for all parameters
• Interfaces:
• Interface RS232 (MODBUS, AK and http / html5 protocol)
• USB port (for memory stick)
• Internal WIFI interface IEEE 802.11 B (OPTION)
• Internal Ethernet 10 BASE-T interface IEEE 802.3 (option)
• Signals:
• 1 to 8 analog outputs 4-20 mA opto-isolated (option)
• 1 to 4 relay contacts programmable (option)
• Display: LCD colour screen (TFT) with LED backlight 320x240 pixels
• Power supply: 90-264 VAC / 1000 VA / 50-60Hz
• Operatings limits: 0 to 40 °C, less than 90% as relative humidity
• CE standards: Electromagnetic compatibility and safety
• EN 61010-1, IEC 61010-1 / EN 61326, IEC 61326
• Enclosure: Wall mounting enclosure (IP65), Coated steel
• Dimensions: 410 x 571 x 255 mm (H x W x D)
• Weight: 27 kg
• Sampling gas:
• Pressure : 0 – 2 Bar Absolute (0 – 2000 hPa Absolute)
• Flow : 0.1 to 10 l/min
• Temperature : ambiant to 400 C
• Fittings : Swagelok, stainless steel 316 for tube OD ¼`` (6.4 mm)
• Zero gas:
• Pressure : 0 – 2 Bar Absolute (0 – 2000 hPa Absolute)
• Flow : 0.1 to 10 l/min
• Fittings : Swagelok, stainless steel 316 for tube OD ¼`` (6.4 mm)