Fully functional isolated analog signal conditioners suitable for PC/104 boards

PC/104 and Small Form Factors — March 5, 2005

Until recently, users usually relegated signal conditioners externally to I/O boards. This configuration resulted in users adding peripheral electronic boards to their systems, substantially increasing both hardware costs and cabinet space requirements. To address these problems, Dataforth designed the SensorLex™ 8B family of isolated analog signal conditioners, which provide Instrument Class® performance in a package only 20 percent the size of competing modular products.

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Figure 1: Miniature-size 8B signal

This new line of high-performance, miniature-size 8B signal conditioners not only represents a technological breakthrough in terms of size and performance, but also offers direct mounting onto the user’s specific I/O boards at a much lower cost compared with other existing external signal conditioners.

The smaller size (see Figure 1, above) is ideally suited for embedded or portable applications, including mobile test stands, COTS military and defense applications (such as in-vehicle testing and airborne electronic instrumentation), highly concealable miniaturized security and surveillance systems, embedded process controls for semiconductor manufacturing equipment, and any other embedded industrial data acquisition system. Because such miniature components did not exist before the 8B, engineers were not able to design data acquisition systems suitable for smaller space requirements in today’s applications. With the SensorLex 8B, however, it is now possible to incorporate high-performance modular I/O on a per-channel basis for any embedded monitoring or measurement and control system. Engineers can achieve this by directly mounting 8B signal conditioners onto the I/O boards. Because the 8B provides an Instrument Class® analog output, it makes interfacing to almost any PC/104, CompactPCI, VMEbus, or proprietary data acquisition board very easy.

The 8B’s advantages in PC/104 applications are clearly evident. The board’s usable 3.5" x 3.5" circuit area provides more than 12 square inches of space – ensuring plenty of room for eight or more 8B analog I/O modules, which measure only 1.11" x 1.65" x 0.4" (28.1 mm x 41.9 mm x 10.2 mm). This configuration’s potential now enables developers to lay out their PC/104 signal conditioner boards (refer to Figure 2) just as they do their A/D and D/A boards, eliminating the need to either mount analog signal conditioners externally to the PC/104 package or construct special back panels and enclosures to contain them.

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Figure 2: Configuration enables developers to lay out their PC/104 signal conditioner boards just as they do their A/D and D/A boards.

Figure 2. Configuration enables developers to lay out their PC/104 signal conditioner boards just as they do their A/D and D/A boards.

The 8B line of miniature isolated analog signal conditioners can interface to a wide variety of analog signals, such as volt, millivolt, current, temperature (thermocouple and RTD), position, frequency, strain measuring devices, and two-wire transmitters.

When interfacing to sensors that are measuring real world physical phenomena such as temperature, pressure, stress, and strain, hazards exist in the environment that can corrupt the measured signal and possibly destroy expensive measuring equipment. Filtering removes unwanted noise from the signal that can appear from adjacent electrical equipment such as welders, fluorescent lights, or electric motors. A signal conditioner then must provide low output noise to ensure it doesn’t add back any of the noise that it just filtered out. The more accurate and linear a signal conditioner is, the more transparent it becomes to the total error budget from the sensor to the A/D subsystem.

Isolation is essential in a signal conditioner to protect the user’s electronic equipment from secondary lightning strikes or accidental connection to high voltages. In fact, there are at least five very real and very different reasons for isolating every analog signal. If you've had problems on past applications, chances are that you experienced one of the following nightmares:

  • Signal crosstalk
  • Common-mode voltages
  • DC common-mode rejection
  • AC common-mode rejection
  • Over-range and input protection issues

The SensorLex 8B isolated signal conditioners address and eliminate such problems.

In addition, a hardware implemented piece-wise approximation technique accomplishes linearization of thermocouple signals. Therefore, the difference between sensor nonlinearity and the 8B module linearization specifies the conformity error. 8B modules use up to five segments to correct nonlinearity, which results in conformity errors as low as a ±0.015 percent span.

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Bill McGovern, North American Sales Manager, Dataforth Corporation holds a B.S. in mechanical engineering from the University of Dayton, Ohio. Bill joined Dataforth in 1995. Previous experience includes 18 years with General Electric in positions of senior sales engineer, product planner, and manager of electric utility market, and 10 years as North American sales manager for Intelligent Instrumentation, a sister company to Dataforth.

Dataforth Corporation, established in 1984 by engineering management personnel from Burr-Brown Corporation (now Texas Instruments), designs and manufactures Instrument Class® electronics for rugged, high performance isolated signal conditioning, data acquisition, and data communication products for industrial and institutional markets.

For more information about Dataforth and the SensorLex 8B family of isolated analog signal conditioners, visit www.dataforth.com.