That’s actually a key problem with the sensors used to monitor and control today’s factories, data centers, offices and other buildings. The fact is, they go out of whack, both predictably over the course of years and unpredictably as the result of manufacturer errors, field exposure, or other factors.
In fact, most building system sensors can be expected to go out of calibration often enough to need replacement every few years, according to John Pitcher, a building controls expert and founder of Scientific Conservation, the building energy efficiency startup now called SCIenergy.
Earlier this year, Pitcher became CEO of Weber Sensors, a main-line German industrial sensor company, with the goal of bringing a new line of self-calibrating sensors to market to help solve this problem. Weber has filed patents on technology to recalibrate so-called calimetric flow and temperature sensors, and is working on patents for humidity sensors as well, he told me in an interview last month.
The goal is to build cell phone chipset-based microprocessors into sensors that can test themselves to see where their readings don’t jibe with reality, Pitcher said. That should be able to keep Weber’s new temperature sensors accurate to within less than half a degree Centigrade, in a provable fashion, for up to ten years, he said.
All the added IT will make Weber’s sensors about one-third more expensive than regular sensors, he noted. But he also expects that the multi-billion-dollar industrial and building controls sensor market will find the return on investment well worth the extra cost.
“People have to appreciate the cost of having inaccurate sensors,” Pitcher said. He first discovered the problem while working with customers of Scientific Conservation’s continuous commissioning and fault detection software, which relies on sensors for its data.
But sensors are built with technology that’s almost guaranteed to go out of true over time, he said. Temperature sensors, for example, use devices called thermistors (or electrical resistors) that change their resistance depending on the temperature, which are molecularly altered in the course of carrying that current, he noted. Humidity sensors, a critical component of outside-air cooling and other HVAC control systems, are notoriously unstable and aren’t expected to last more than two years or so, he said.