Putting emissions testing on the road: Sensors Inc. developed on-board emissions testing equipment for diesel, gasoline engines; selected by EPA - Test Equipment

Diesel Progress North American Edition, Oct, 2002 by Mike Brezonick

For all the sophistication and capabilities of modern engine and chassis dynamometers, gas analyzers and data acquisition systems working in labs all over the world, there is still no substitute for in-field testing. Only in the real world, an engineer once commented, "can you find the snakes under the rocks."

For more than 30 years, Sensors Inc. has specialized in engine test equipment such as gas analyzers and opacity meters. Over the past four years the company has shifted its R&D focus toward the development of on-road, in-use testing systems. "No matter how sophisticated you make a laboratory test procedure, it will never truly replicate in-use operating conditions," said Andrew Reading, president of the Saline, Mich., manufacturer. "The only accurate way to get results is to monitor the vehicle as it goes through its normal duty cycle under real-world conditions."

To achieve that purpose, the company has developed on-vehicle analysis systems for in-use testing of diesel and gasoline vehicles and equipment. And its technology achieved a strong measure of validation in late summer, when Sensors Inc. was awarded a contract from the U.S. Environmental Protection Agency to supply on-vehicle emissions analysis systems for its testing programs.

"This is truly a major milestone for our company," said Reading. "We've worked hard to position ourselves as the industry leader in developing analytical equipment that monitors the actual emissions produced while vehicles are being driven on the road.

"EPA is now talking in terms of not-to-exceed emissions limits and our devices will determine whether the vehicle is in or out of that not-to-exceed zone. Later on, the calibrators, the R&D people and the engine development people can go back, look at the record and really see what the vehicle was doing when the emissions went outside the zone."

Sensors Inc/ SEMTEGH (Sensors Emissions Measurement Technology) systems are designed to provide immediate analysis of key exhaust gas components, including total hydrocarbons (THC), oxides of nitrogen ([NO.sub.x]), carbon monoxide (CO) and carbon dioxide ([CO.sub.2]) Using Sensors Inc.'s proprietary NDUV (nondispersive ultra violet spectroscopy) module, the NO and [NO.sub.2] constituents of NOx can be measured simultaneously and independently Measuring 22 in. long, 17 in. wide and 14 in. high, the SEMTECH-D (diesel) unit is little larger than a piece of carryon luggage, the company said, and the gasoline version (SEMTECH-G) is slightly smaller. The diesel unit weighs approximately 70 lb. and typical installation time is under 30 minutes. Both the diesel and gasoline versions can be rack or cart mounted and they are ruggedized for use in both on- and off-road applications. Key construction features enhancing its durability include epoxypotted electronics, isolation-mounted circuit boards and heavy-duty electri cal components.

The SEMTECH-D system is typically installed on the vehicle or machine to be tested and only two connections are required. One is to the tailpipe to draw the exhaust sample and the other is to the vehicle's diagnostic connector, which gives the system access to the vehicle's data stream.

All of the exhaust parameters are measured continuously while the vehicle or equipment is being operated. In addition, all of the vehicle data coming off the data stream is logged.

The SEMTECH-D can measure the following gas concentrations:

* [CO.sub.2] -- zero to 20 percent.

* CO -- zero to 1 percent.

* THC -- zero to 1000 ppm.

* NO -- zero to 3000 ppm.

* [NO.sub.2] -- zero to 500 ppm.

The system can also be used to measure [O.sub.2] at concentrations up to 21 percent. When reporting concentrations for exhaust constituents, accuracy of the SEMTECH-D system is typically within [ or -]3 or 4 percent, the company said. Reporting on electronic engines can be done in g/Bhp-hr or g/mile, while on engines without electronic controls, additional instrumentation is provided to deliver g/Bhp-hr. "Portability would mean little if accuracy suffered," Reading said. "But SEMTECH-D offers lab-quality accuracy in a portable unit. Recent correlation testing with a Caterpillar C-10 engine demonstrated just how closely SEMTECH-D follows lab results."

The SEMTECH-D system has a flow rate of 3.0 1pm and an ambient operating temperate range of 0[degrees] to 40[degrees]C after a 30-minute warm up. Data is captured at a rate of 1 Hz.

In addition to collecting performance data under real-world conditions, SEMTECH-D can also be used in other testing applications, including engine and vehicle sub-system development; catalyst and particulate trap tesing, vehicle compliance testing; documenting drivability problems; developing engine and vehicle electronic control strategies and calibrations; and end-of-line production testing.

Reading said that the system can also be outfitted with an optional GPS unit to provide vehicle location monitoring. Other options include exhaust flow measurement capability and a mobile cart.

Test data can be retrieved remotely using optional wireless, cellular or satellite links or it can be taken directly from the unit's message center. The message center also displays instrument status, operating condition, fault diagnostics and remote communications status.