Interview - November 2001
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EMAIL INTERVIEW Steve Allison & Ken Sinclair

Steve AllisonSteve Allison is the marketing manager at Building Automation Products, Inc. BAPI specializes as a manufacturer of temperature and humidity sensors for the HVAC/R industry. Steve's background includes various positions in administration, research and development, production, shipping, sales, and marketing; giving him a unique perspective on the many facets involved in a manufacturing company. Steve holds a BS in Applied Optics from Rose-Hulman Institute of Technology, is based in Madison, WI, and can be reached at  or through the website

Are all sensors the same?

Sinclair - Are all sensors the same?

Allison: Many of the people we talk with suggest that "sensors are all the same", "price is the only real difference between sensors", and "it doesn't matter if they fail because we can get replacements the next day". We believe the idea that sensors are commodity products is on the way out. In reality, the details in the design and manufacture of sensors make a big difference in accurate measurement and long-term performance. Is there really "an acceptable number of failures" because replacement are only a day away? We say NO! Sensors should install easily, provide accurate readings, and perform for the LIFE OF THE JOB. We believe that the installed cost over the life of the job is what is important, not just the purchase price.

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Sinclair - What is the role or importance of sensors within building automation systems?

Allison: Sensors are the first critical factor in a effective control strategy. People will say "you could argue that point about any component within a control system". This is true, a control system is simply a chain or sequence of events and if any one piece is missing or doesn't work, the system breaks down. However, sensors are potentially the first weak link in the chain. You may be familiar with the saying "garbage in, garbage out" as it relates to computers and computer programming. This idea applies to building automation systems too. In essence, the sensors can make or break the control system. If we look at it from the customer's perspective, this fact is further enlightened. The end user sees the complete system, not the components. The "system" either works or it doesn't, and if it doesn't work, the customer is not happy. Unhappy customers mean lost business. Therefore, choosing a quality, dependable sensor is a crucial step in the design and installation of a building automation system.

Sinclair - What are the key issues relating to sensors?

[an error occurred while processing this directive]Allison: The key issues can be grouped into three stages - production, selection, and use. Production is the first stage, and involves the design, packaging, and manufacture of the sensors. Ensuring accurate, long-term performance starts with a solid design. This design should take into account the applications and environments the sensors will encounter in the "real world", and should utilize high-quality, reliable components. In our designs, we address issues such as placement of heat generating components (keeping them away from the sensor minimizes errors) and which type of circuit board to use (double-sided, through hole boards ensure better electrical connections and more durable mechanical connections). Packaging ensures long-term survival under unexpected conditions. Many times condensation is formed in or around a sensor due to unseasonable temperature swings or other factors beyond our control. We protect our sensors by using etched Teflon, insulated leadwires, and by providing sealant filled connectors for terminations - believing that preventing a problem is better than fixing one in the field. When high moisture conditions are expected, we employ measures (such as our IP 66 rated EU enclosure and encapsulated circuitry) to safeguard against moisture infiltration and virtually eliminate failures. As the sensors are manufactured (soldered, calibrated, assembled, and 100% tested), technical expertise and attention to detail are very important. Very often, a sloppy solder joint or over heating a component will shorten a sensor's life span.

The next stage is selection, and involves specifying, identifying, and applying sensors. Although this stage is somewhat beyond our control, as we do not directly write specifications or choose which sensor to use, we strive to provide advice and technical support as best as we can. For example, our new Sensor Handbook and CD includes sample sensor specifications and application recommendations. We are always available to answer questions or provide assistance in identifying which sensor would work best in a particular application. BAPI president, Ritch Stevenson, clearly expresses our position in saying, "I believe the technical guidance we provide is every bit as important as the products we manufacture."

The final stage is use, and involves installation, termination, and maintenance . This stage is where many problems occur because it is the most unpredictable stage. Proper installation is more than just mounting the sensor on the wall or duct. The sensor must be installed in the correct orientation, in an area with proper airflow, and away from any possible sources of error (sunlight through a window, a copy machine, at the bottom of a staircase, etc.). Then, once installed, the sensor must be terminated carefully and correctly. This not only means connecting the sensor outputs to the controller inputs correctly (sensor output A to controller input A, appropriate wire gage, shielded cable if needed, etc.), but also means using some old-fashioned, common sense (bench test or dry run at one's shop, minimal torque on the terminal blocks, terminate with power off, etc.).

Sinclair - What are your biggest challenges?

Allison: We have three major challenges in providing sensor solutions to the industry. 1) Effectively and efficiently informing the industry of new technologies and product improvements. There are those in our small part of the industry, as well as throughout, who make this education process difficult by wasting people's time. We strive to help our customers or provide some kind of value with every contact. 2) Breaking out of the "lowest-is-best" trap. Just as the lowest bid is not always the best, the least expensive sensor is not always the best long-term solution. Paying a little more up front for a quality product can save hundreds or even thousands of dollars in labor and service calls, over the life of the system. 3) Setting a high standard and eliminating the "all sensors are created equal" mentality. As I said in the beginning of this interview, sensors should install easily, provide accurate readings, and perform for the LIFE OF THE JOB. Problems and failures should be few and far between. We need to remember that the details in the design and manufacture of a sensor DOES make a difference in its long-term performance, and reliability.

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