the accuracy of Watlow's existing thermocouple and RTD sensors by a minimum of 50 percent.

"INFOSENSE in a generic sense is using information about a temperature sensor in order to improve its performance," said Chris Seymour, strategic marketing manager. "Some information already exists for free through manufacturing the sensor. We're working to innovate how to more easily provide and use that information. The cost of processing information is getting cheaper and cheaper, so while working with the basic 'free' information is an easy first step, we're then taking that philosophy to the utmost with full-blown smart sensors that automatically link the application to a knowledge base – calibration lab data, for example."

"Using a three-segment error correction at least doubles the sensor's accuracy," Seymour said. "It's free on standard thermocouples, and an inexpensive option on RTDs."

As an example, the accuracy of an ASTM E230 "special limits of error thermocouple" improves to one-half special limits. A Type K has an accuracy of ±1.1°C or 0.4 percent and with INFOSENSE, it becomes ±0.55°C or 0.2 percent, according to Watlow. In another example, a DIN-IEC-751 Class A accuracy RTD probe becomes a one-half Class A accuracy probe. A DIN Class A has an accuracy of ±0.15°C and with INFOSENSE that accuracy becomes ±0.08°C.

Seymour explained that a SERIES SD controller user, when installing the sensor, inputs the four three-digit numbers from the tag and the SD then knows how much error the sensor has at what temperatures. It then performs its simple three segment line correction. An option with the SERIES SD controller is a bar code reader, which helps automate this step.

Watlow has also developed an INFOSENSE-P version, which is designed for plug and play smart sensors. Instead of a special tag like INFOSENSE, the INFOSENSE-P sensors have inside them an EEPROM (memory chip), which is programmed with varying levels of sensor information. Basic levels of information include: manufacturer, model number, serial number, measurement range, calibration information, or other (name, location, etc.)

"The EEPROM can now hold much more than four data points, so we program the full error curve from our calibration lab into the sensor," Seymour said. "When the sensor is wired or connected to compatible electronics, such as our SERIES PD controller, the sensor's memory chip has a direct path into the controller's microprocessor. The controller then takes that information, and in the case of calibration information, performs a full high-order curve fit to correct for all the known error. The result is a sensor that is now highly accurate."

The SERIES SD controller is a panel mount single loop controller with a front display panel and is INFOSENSE compatible. The SERIES PD controller is a DIN-rail mount dual input single loop controller with embedded Ethernet communication, and is INFOSENSE-P compatible. Watlow has partnered with National Instruments to help in the adoption of these new plug and play sensors, based on the IEEE P1451.4 plug and play sensor standard.

"INFOSENSE in a generic sense is using information about a temperature sensor in order to improve its performance." Chris Seymour, Watlow strategic marketing manager

"We've developed a nonstandard thermocouple we're calling the WATCOUPLE that uses Alloy 600 and nickel-silicon to make a thermocouple that is four times more accurate than Type K special limits, and lasts three times longer with three times less drift than Type K. A WATCOUPLE is more accurate than a Class A RTD above 100°C, and being a thermocouple has natural advantages, such as having very high temperature limits in small sizes," Seymour said.

In a related development, Watlow's new DEVICENET temperature transmitter enables this smart sensor technology to install large amounts of sensors onto a simple DEVICENET network, simplifying and saving money on wiring. DEVICENET is then incorporated into a system PLC or software-based system, such as LabVIEW^®.

"INFOSENSE-P provides error-proof automation of the traceability information," added Seymour. "The smart sensors can also include their identity information, so that when a sensor is plugged in, it automatically tells the instrumentation its name — air inlet, for example. This saves time debugging which sensors are installed where, automates documentation and thereby can further reduce testing costs."

Improved accuracy and reduced sensor drift also enables a more accurate predictive maintenance (PM) to be performed. For example, if the PM software monitors temperature of a part of an engine, then the limitations of that software to make decisions on the health of the equipment are limited by the quality of the information received from the temperature sensor. Not only is a higher degree of accuracy desired, but more importantly a temperature sensor that drifts less over time makes that software more accurate, dependable and ultimately far more powerful.

"Our WATCOUPLE is specifically designed to dramatically improve performance for these types of applications," Seymour said.

He continued, "The costs of processing information continue to decrease. For the more demanding temperature measurement applications, the smarter money is spent on the quality of the calibration information and more stable materials to assure that the information remains valid for longer."

Reprinted with permission Diesel and Gas Turbine Worldwide, July/August 2003. LabVIEW^® is a registered trademark of National Instruments, Inc.

Challenge: Watlow's customer was experiencing failures in their single and three-phase SCR relays from another supplier. Watlow wanted to understand the reason for the failures before providing a solution so Watlow offered to assist in diagnosing the problem.

After evaluating a failed unit, it was established that although the customer had taken steps to keep the ambient temperature in the enclosure below the competitor's rating, the unit had failed due to overtemperature.

Solution: Watlow sampled a 22 mm (0.86 in.) SERIES CZR for the single-phase application. The extra space provided by the controller's small footprint, in addition to the superior internal heat transfer, ensured the SERIES CZR's success.

The customer also purchased a Watlow DIN-A-MITE^® B for the three-phase application.

Both power controllers are stock items and were available to ship the same day.

Both Watlow and its customer are pleased with the results. Both power controllers fit the application perfectly and are proven reliable. Six months after the installation there are zero failures.