Instrument Development:

Diode-LASER based Realtime Gas Monitors

SSI's DiRTiGAS sensors use tunable diode laser (TDL) absorption to provide selective measurement of HCl, HF, HBr, HCN, CO, OH, carbon dioxide, oxygen, hydrogen sulfide, acetylene, methane, ammonia, nitrogen dioxide, water vapor, and other small-molecule gases. These automated sensors provide fast and accurate ppm-level measurement of air toxics, combustion and other gases in a variety of ambient air and stack monitoring applications. The patented DiRTiGAS technology has been implemented by SSI in custom and prototype systems and in a new commercial in-situ stack gas monitor.

DARCS Sensor for Open-air Paths

NIR Tunable Diode Lasers Provide Performance Advantages - Near infrared (NIR) diode lasers, originally developed for the communications industry, combine small size, high reliability and long lifetime with extremely high spectral resolution. Rapid modulation of the diode laser wavelength provides sensitive, selective detection of gas concentration, temperature, and pressure in rapidly fluctuating environments. In combination with fiber-optic components, these lasers enable intrinsically safe remote detection in harsh environments, such as flames, smoke stacks or gas reactors.

Turn-Key Sensor Systems -SSI is at the forefront of research and development to harness the unique properties of diode lasers for industrial environments. DiRTiGAS combines these lasers with patented line-locked absorption techniques to achieve turn-key, automated operation in compact and rugged packages. There are no consumable components or moving parts, and all systems can be configured for different gases by changing the laser source module. In addition, different sampling geometries (including fiberoptic, sample cell, or open path) have been developed for a wide variety of applications.

Proven Technology for Process Gas and Ambient Air Monitoring

Long-Path Ambient Air Monitor - An open path monitor originally developed by SSI for the Department of Energy to study atmospheric carbon dioxide and water vapor has been used to measure pollutants and trace gases such as ammonia, acetylene, and nitrogen dioxide. Average gas concentrations are measured over meter to kilometer paths between the transceiver module and a retroreflective target. This man-portable instrument can be used for chemical surveying or can be installed for permanent, unattended fence-line or area monitoring of gas leaks and fugitive emissions.

A second-generation version of this sensor is designed for stationary installation in industrial environments. It uses SSI's patented Off-Line-Locked Detection System (OLDS) to simultaneously monitor multiple chemical species. The initial test application was the measurement of HF, water vapor, and methane in an aluminum smelter pot room. In a three-month side-by-side test against another optical instrument and EPA Method-14, the OLDS monitor delivered the highest-quality short-term-measurement of HF while demonstrating equivalence with the 48-hour Method-14 data.

OLDS Open Path Sensor Installed in an Aluminum Pot Room

GASMAN Portable Multiple Toxic Gas Monitor - Motivated by the Army's need for improved toxicology instrumentation, Spectral Sciences has developed a suitcase-sized, battery-operated system for simultaneous measurements of two or more gases. The GASMAN system uses multiple laser modules and a multiple-pass sample cell to provide rapid-response measurements of HCl, HBr, CO, nitrogen dioxide, carbon dioxide, and hydrogen sulfide with sensitivities below the threshold limit value and a dynamic range of five orders of magnitude.

GASMAN Portable Multiple Species Monitor

In-Situ Stack Gas Monitor for Pollution Control This system, developed jointly by SSI and Monitor Labs, Inc., is an in-stack ammonia monitor for NOx control in specific catalytic reduction systems. In contrast to extractive systems, the optical measurement is performed directly in the stack, avoiding problems with sample transport, contamination, and decomposition. The direct optical measurement is made possible by a unique, in-situ probe head design which is capable of withstanding hot, fouling environments.

Combustion Product Profiling System - Spectral Sciences met NASA's requirements for rocket engine combustion diagnostics with the MEDUSA fiberoptic system for spatially resolved measurements of carbon monoxide, carbon dioxide, and acetylene in the rocket exhaust plume. The system provides simultaneous measurements along seven different lines of sight through the hot combustion zone, and has also been used to measure water vapor, OH and CO spectra at temperatures up to 3,000 K.

MEDUSA Fiberoptic Monitor for Multiple Lines-of-Sight

R&D and Custom Sensing Systems for Your Needs

SSI is actively involved in research on and development of higher sensitivity, longer wavelength diode laser monitoring systems as well as techniques for measuring molecular and radical species in high temperature combustion environments. SSI is also continuing to develop custom products for government and industry. If you need to measure concentrations, temperatures, pressures or velocities in a difficult environment, Spectral Sciences can customize technology to meet your requirements.

For more information please contact Dr. Neil Goldstein at neil(at)spectral.com.