Dataforth Adds Strain Gage Modules to 8B Family of Isolated Analog Signal Conditioners

Dataforth Corporation of Tucson, Arizona, has just introduced the latest additions to its family of SensorLex® 8B isolated analog signal conditioners: 8B38 strain gage input modules with a choice of 3Hz or 8kHz signal bandwidth.

These modules provide excitation to strain element-based sensors, then isolate, filter, and amplify the resulting sensor output and provide high-level analog voltage output. Available models provide excitation voltage choices of 3.333V or 10.000V, allowing connection to sensors with nominal impedance from 100ohms to 10k-ohms.

Constant voltage sensor excitation is standard in 8B38 modules using a voltage source that is precisely regulated to minimize changes over time, temperature, and power supply voltage.

Specific applications for the new modules include the following:

• Any process, industrial or other, that requires precise measurement of strain or pressure; as 8B38 modules have a low drift over time and temperature, they do not add significant measurement error
• Situations where space is at a premium; 8B38 modules provide signal conditioning in the smallest package available on the market
• Vibration analysis in machinery health and other high frequency monitoring applications, using the 8kHz wide bandwidth option
• Monitoring slow varying processes, such as conveyor belt systems, and applications where rejection of high frequency noise is important, using the 3Hz narrow bandwidth option

Signal gains of 167V/V to 500V/V are offered with the 8B38, allowing the modules to connect to industry standard sensors with output sensitivities of 2mV/V and 3mV/V. Other ranges also are available upon request.

Signal filtering in the 8B38 modules is accomplished with a 5-pole filter optimized for time and frequency response, which results in greater than 100dB of normal-mode rejection for signal frequencies above the pass-band. In the case of models with 3Hz signal bandwidth, rejection of 60Hz frequency content is greater than 70dB. One pole of the filter is on the field side of the isolation barrier for anti-aliasing purposes and the other four are on the system side.

As excitation current flowing in sensor leads can cause significant measurement errors, especially when long sensor lines are required, 8B38 modules will soon be available upon request with a constant current source for sensor excitation. This is of paramount importance in minimizing errors when long lines are used to connect to the sensor, and it eliminates the need for 6-wire connections to the sensor. With this option, sensor output will be accurately measured, regardless of voltage drops in the sensor lines; constant current excitation is also used in high temperature applications.

To ensure protection of expensive data acquisition equipment, the 8B38 module signal inputs and sensor excitation outputs are protected against accidental connection of voltages up to 240Vrms. All models are designed for operation in Class I, Division 2 hazardous locations and are compliant with European EMC directives.

Additional 8B38 key features, also common to Dataforth’s entire 8B family, include:

• 1500Vrms Transformer Isolation
• ANSI/IEEE C37.90.1 Transient Protection
• Input Protection to 240VAC Continuous
• Low Drift with Ambient Temperature
• -40°C to +85°C Operating Temperature Range
• 5V Power
• UL Listing Pending
• CE Compliant
• Mix and Match Module Types on Backpanel

Developed in response to customer requests worldwide for smaller, lower cost isolated signal conditioners, the SensorLex® 8B family ensures fully functional Instrument Class® performance in a package only one-fifth the size of competing modular products. Since its introduction, the 8B line has grown to include 17 family groups with a total of 102 modules that interface to a wide variety of analog signals such as volt, millivolt, current, temperature (thermocouple and RTD), position, frequency, and strain measuring devices.

Measuring only 1.11 x 1.65 x 0.4 inches (28.1 x 41.9 x 10.2mm), the 8B signal conditioner is 80% smaller than similar products, making it ideal for embedded or portable applications such as mobile test stands, COTS military and defense applications, miniaturized security and surveillance systems, and embedded process controls for semiconductor manufacturing equipment. With the SensorLex® 8B, 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; because the 8B provides an Instrument Class® analog output, interfacing to almost any PC/104, compact PCI, VMEbus, PXI, or proprietary data acquisition system board is very easy.

Housed in a solid, potted thermoplastic plug-in-the-panel package with flammability rating of UL-94 V-0, the 8B family of isolated signal conditioners is specifically designed to protect user equipment, while reducing electrical noise and enabling convenient system expansion and repair. All 8B modules offer dimensional stability over temperature, chemical resistance, and excellent stability over time; they do not require recalibration.

Operation and storage temperature for the 8B models is -40°C to +85°C; relative humidity range is zero to 95% noncondensing. All models meet the requirements of EN61000-6-4 (radiated/conducted emissions) and EN61000-6-2 (ESD/RF/EFT immunity). For operation in hazardous environments, North American Class I, Division 2, and European Group II, Category 3, approvals are pending.

Design-in accessories for the 8B line include a selection of backpanels (2, 4, 8, and 16 channels) that provide screw-terminal inputs and outputs as well as a DB25 header connector that connects 8B outputs to a user’s data acquisition system. The DB25 header can be matched with 1, 2, or 7 meter cables, available as accessories, to connect sensors and transducers to an external 25 screw-terminal interface board.

Coming months will see the introduction of 2-wire transmitter interface modules, frequency input modules, and voltage output modules. Custom signal conditioning models are available to meet unique signal conditioning needs, and the 8B line will soon be available in a DIN mount configuration.

For additional information and pricing, call 800-444-7644 toll-free, or e-mail at sales@dataforth.com.

Original release: December 13, 2005