What Are the Key Components of an NH3 (Ammonia) Analyzer?

NH₃ (ammonia) analyzers enable professionals to measure ammonia (NH₃) concentrations in ambient air. NH₃  can be hazardous to one’s health.

What technology is involved in being able to monitor this gas? Here are the key components of an NH₃  (Ammonia) analyzer:

• The NO₂-to-NO converter heats molybdenum to approximately 325 °C in order to convert and detect NO₂. The converter consists of an insulated housing, heater, replaceable cartridge, and a type K thermocouple sensor.
• The mode solenoid valve switches analyzer operation between the NO mode and NOx mode. It routes the ambient air sample either through the reaction chamber (NO mode) or through the NO₂-to-NO converter and then to the reaction chamber (NOx mode).
• The NH₃ converter heats stainless steel to approximately 750 °C in order to convert NH₃ . The converter consists of an insulated housing, ceramic heater, replaceable cartridge, and a type K thermocouple sensor.
• The reaction chamber is where the sample reacts with ozone and produces excited NO₂ that gives off a photon of energy when it decays. The reaction chamber is heated and controlled to approximately 50 °C in order to ensure the greatest instrument stability. The sample and ozone flow capillaries and a thermistor sensor are also housed in/on the reaction chamber assembly.
• The optical filter housed in the reaction chamber limits the spectral region viewed by the detector and eliminates possible interferences due to other chemiluminescent reactions.
• The pressure transducer measures the reaction chamber pressure. The sample flow sensor located at the reaction chamber inlet measures the sample flow into the reaction chamber.
• The Ozonator generates the necessary ozone concentration required for the chemiluminescent reaction. The ozone reacts with the NO in the ambient air sample to produce the electronically excited NO₂ molecules.
• The ozonator flow switch located at the ozonator inlet completes an electrical safety circuit when air flows through the sensor to the ozonator. If airflow stops, the flow sensor breaks the electrical circuit to the ozonator and shuts it off to prevent the ozonator from overheating.
• The Photomultiplier tube (PMT) provides the infrared sensitivity required to detect the NO₂ luminescence resulting from the reaction of the ozone with the ambient air sample. Optical energy from the reaction is converted to an electrical signal by the PMT and sent to the input board that transmits it to the processor.
• The thermoelectric PMT cooler reduces the PMT temperature to approximately -3 °C to minimize dark current and increase instrument sensitivity. The cooler helps to increase zero and span stability over a wide ambient temperature range. The cooler housing also shields the PMT from external electrical and optical interferences.
• The external pump draws the reacted gases out of the reaction chamber.
• The dry air capillary along with the pump is used to control flow in the dry air line.
• The ammonia scrubbers are mounted internally and remove ammonia from the sample air.
• Software, Communication, Connector, Sensor, Assembly and Power Supply Components are used throughout the analyzer.

Other components that may be available for your instrument:

• With a zero/span assembly option, a source of span gas is connected to the SPAN port and a source of zero air is connected to the ZERO port. Zero and span gas should be supplied at atmospheric pressure. It may be necessary to use an atmospheric dump bypass plumbing arrangement to accomplish this.
• A permeation dryer minimizes routing maintenance procedures by providing a continuous stream of dry air to the ozonator (using the selective water permeation characteristics of the dryer). With the permeation dryer option, it is not necessary to constantly replenish the ozonator air-drying column as in the standard instrument.
• If a Teflon® element filter is installed (just prior to the SAMPLE bulkhead) all calibrations and span checks must be performed through the filter.
• An ozone particulate filter minimizes the potential for contamination of the ozonator by trapping any particulate matter before passing through the ozonator.
• An I/O expansion board provides six analog current output channels (0- 20 mA or 4-20 mA) and eight analog voltage inputs (0-10V).
• Optional terminal block and cable kits provide a convenient way to connect devices to the instrument.

For additional details, consult the user manual or contact your manufacturer’s representative.

Editor’s Note: Additional information:  Ammonia Chemiluminescent Gas Analyzer Product Specifications

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