| Model 518 | PC/104 8-Channel Smart Sensor Interface | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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DescriptionModel 518 is a PC/104 board that offers a compact, low-cost solution for acquiring data from up to eight sensors at up to 16-bit resolution. Each channel can be individually configured for any supported sensor type. Sensor data are linearized (if necessary) and made available to the host computer in engineering units (e.g., degrees C, ohms). Complete signal conditioning is provided for thermistors, RTDs, thermocouples, strain and pressure gages, and resistance and voltage inputs. The board features built-in excitation circuitry for passive sensors. Model 518 block diagram
The board's microcontroller continuously scans the enabled sensor channels. Analog-to-digital conversion is performed in under 22 milliseconds, resulting in a 45 channels-per-second scan rate. When scanned, each channel is excited, amplified, digitized, filtered, linearized, converted to engineering units, and stored in on-board memory, independent of host CPU activity. The host can quickly retrieve the most recent sample from each channel so that it never needs to initiate or wait for a data conversion. Fully electronic calibration eliminates trim potentiometers and the need for board access. Calibration data is stored onboard so that Model 518 boards can be easily installed and interchanged and no system calibration is required. All field wiring is accessible through a single 40-pin header. The header may be connected to a custom termination system or to any of several standard breakout boards available from Sensoray. ExcitationSensoray's exclusive pulsed excitation system is used to provide stimulus for passive sensors. By pulsing the excitation, this system reduces sensor self-heating and also helps to minimize board power consumption. The board's excitation system is dynamically reconfigurable. The circuit topology of the excitation source changes as needed to adapt to the type of sensor that is being measured. A pulsed constant voltage is applied to strain and pressure sensors, while pulsed constant current is applied to passive resistive sensors such as RTDs. Each channel includes provision for a four-wire sensor connection, thus eliminating lead loss errors in RTD's, thermistors, and resistors. ThermocouplesThermocouples are widely used in industrial measurement and control applications because of their relatively low cost and extensive temperature ranges. In particular, thermocouples excel at measuring high temperatures where other common sensor types cannot function. Model 518 includes support for an external cold junction compensation (CJC) sensor, which is required for thermocouple measurements. A CJC sensor is built into all of Sensoray's standard 518-compatible termination boards. The CJC sensor is measured by a dedicated analog input channel so that the eight sensor channels will always be available for application use. SoftwareA free software development kit (SDK) is available to enable system integrators to quickly develop applications for Model 518. In addition, an optional data logging program, QuickSense, allows quick and easy configuration, real time display and logging. Typical Application
Specifications
Supported Sensors
Documentation
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