December 2004
  
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TRANSDUCER TECHNOLOGY
a breath of fresh air for rodents

Noel J. Barrette
Marketing Communications Manager
Setra Systems, Inc.

Case Study

Keeping a clean and steady flow of air is extremely important in any enclosed environment, and particularly so in a lab environment where isolation and control of all elements and potential containments is so essential. That’s where the Air Flow Technology (AFT) engineering staff at Allentown Caging Equipment put their energy when designing their new generation of animal caging systems.

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The driving force in terms of innovation and product development at Allentown Caging, the AFT department is responsible for designing and developing a range of airflow related products. For over 35 years, the company has been providing the biomedical research community with the most technologically advanced animal housing systems. Recently, the AFT department designed two new products that offer improved ventilation of Allentown Caging’s P/NC Positive/Negative Control Systems.

The P/NC System is an individually ventilated caging system with 60 to 160 cages designed to hold up to 800 mice, rats, guinea pigs or other rodents. These safe and flexible environments are HEPA filtered, and can switch from positive to negative pressure at the “press of a button,” providing a safe environment for both the animals and laboratory personnel. These caging systems use microprocessor controlled supply and exhaust blowers to provide the required number of controlled air changes per hour. To help ensure that the systems maintain a stable air flow, and to measure air flow both into and out from the cages, Allentown Caging’s Air Flow Technology AFT team turned to Setra Systems of Boxborough, MA and that company’s differential pressure transducers.

Handling the pressure.
With more than 35 years experience in the design and manufacture of pressure measurement systems for HVAC control, Setra’s Model 265 differential pressure transducer was a perfect fit for the AFT team’s air flow monitoring and control needs. The team selected the Model 265, which is offered with ±0.25% accuracy (±0.4% optional and ±1% standard) in pressure ranges from ±0.1” W.C. up to 100” WC. The Model 265 provided the excellent stability and high level output that is required for high-efficiency, air control systems.

differential pressure transducers“We considered some less expensive options,” said a project engineer at Allentown Caging Equipment. “But we determined that Setra had the high level of quality and accuracy we were looking for – specifically accuracy in low range applications.”

The Setra 265 is a key component in Allentown Caging’s SE6100 Smart Exhaust Pak, the unit that’s responsible for extracting air from the P/NC System’s animal cages. Custom-made for the P/NC System, the Smart Exhaust Pak features a microprocessor control board and “feed-back” control technology to automatically adjust the blower speed and maintain the desired 15-50 CFM airflow as the HEPA filters begins to load. The Setra 265 pressure transducer allows the SE6100 to constantly monitor the flow of evacuating air – air that’s replete with airborne particulates like dander, bedding and dust, as well as potential pathogens.

Allentown uses mass flow sensor technology with a hot tip anemometer on their supply blower to control the fan motor and adjust for HEPA filter loading. The problem with using this method for an exhaust system is that the delicate sensor would be exposed to airborne particles. This mass flow technology would require constant cleaning. These particles would block the hot tip and cause the unit to go out of calibration and greatly detract from accuracy. The Setra Model 265 allows Allentown to measure and monitor the pressure, permitting the Smart Exhaust Pak to precisely measure and control the P/NC System’s airflow accurately, and without the added costs of re-calibration and additional maintenance.

Reliable Controls Detection made easy.
The Setra 265 is also central to Allentown Caging’s Range Finder Rack Flow and Cage Flow Detectors, which are also used with the P/NC cage rack. The Range Finder Rack Flow Detector provides supply or exhaust air confirmation for an entire ventilated rack, while the Cage Flow Detector provides cage-level airflow confirmation as low as 0.15 CFM, from cage to cage. The Range Finder products can be used while the ventilated rack is in service, and fully populated, with no disruption to its inhabitants. Both of these detectors utilize Setra’s transducer technology to provide simple, easy to read analog output, and accurate pressure measurement. The 265 transducers used in Range Finders measure low differential pressures from 0 to ±0.25” WC with a high level output accurate to +/- 0.4% of full scale.

“Our customers need to know how much fresh air their animals are getting in “real time,” said an engineer at Allentown Caging Equipment. “The Range Finder products with the Setra technology provide the simple and fast verification our customers are looking for – as easy as a green light for airflow that’s within the selected range, typically ±10%, and a red light signifying unacceptable airflow falling outside that range. Within seconds, the Range Finder solutions allow users to spot check every rack and every duct connection in the cage system.”

By taking advantage of the Setra 265’s precise pressure measurement and tight tolerances, Allentown Caging’s Air Flow Technology team was able to produce easy-to-operate air measurement and control solutions that don’t require an abundance of extra parts. Which means - with the P/NC Positive/Negative Control System serving as an environmentally sound cage system, the system’s residents aren’t the only ones who can breathe easier.

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