PARxCH USER MANUAL EXCERPTS

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The table of contents and selected excerpts from the PARxCH manual are shown below. The full text is available in PDF format at no charge from our downloads page.

CHAPTER 1: INTRODUCTION
The Symmetric Research PARxCH are a family of 1, 4, and 8 channel 24 bit A/D data acquisition systems for acquiring high resolution data on the PC at sampling rates from DC to several kHz. Connecting to the PC parallel port, each sits outside the PC in its own vinyl covered steel enclosure for quiet noise free operation. Because they interface to the parallel port, the systems are easy to use with closed PC's such as laptops. For PC104 applications, an adapter plate is also available so the PAR4CH can be used as part of a standard PC104 stack.

Based on the Burr Brown ADS1210 24 bit sigma delta A/D converter, the PARxCH has an individual converter per channel architecture. This minimizes channel cross talk, skew, and settling time. You get the full performance of a dedicated A/D converter on each channel. The ADS1210 converters are "instrument grade" meaning they maintain full accuracy right down to DC. In addition, data from the A/D converters is buffered with a deep 2Mb memory array on the PAR4CH. This allows for continuous data acquisition even with long PC task switching latencies.

Software that comes with the board has both high level finished applications ready for immediate use and low level function libraries for those wishing to do custom programming. Support is provided for DOS, Windows, Linux, and LabView. The WinNT/2K/XP and Linux software feature true kernel mode drivers for good performance and reliable operation.

Other items included with the board are a 9vdc wall transformer, a cable for connecting to the PC parallel port, an analog input terminal board, and circuit diagrams. Everything needed to be up and running right away.

CHAPTER 2: INSTALLATION
Installation of the PARxCH is straightforward. You'll need to plug in the wall transformer, connect to the PC parallel port, install the software, and provide suitable analog inputs. The individual steps in more detail are:

CHAPTER 3: FINISHED APPLICATIONS
The SR PARxCH comes with finished application programs you can run immediately after installing the system. These programs will help you become more familiar with the system and may also fill your entire acquisition needs. The source code is included for those wanting to modify these programs for custom applications.

The simp and scope programs have both been written in C. Simp is a simple text only command line program, while scope has a full Windows GUI graphical interface and display. Under Linux, only the simp program is available.

In addition to these basic data acquisition programs, the PARxCH software also includes several other interesting programs. These are briefly described below.

CHAPTER 4: LIBRARY FUNCTIONS
The library functions are at the core of the software supplied with the SR PARxCH. They allow users to control board operations from high level languages without having to know the low level details of how the system operates. These functions can be statically linked to C programs for any OS. In addition, they are available as a Dynamic Link Library (DLL) under Windows and as a shared library (.so) under Linux. When used as a DLL, these functions can be called from other high level programming languages such as Microsoft Visual Basic and National Instruments LabView. This chapter covers usage from programming environments like Visual C. For information about usage from LabView, see the LabView chapter. For data acquisition applications that are ready to run with no programming required, see the Finished Applications chapter.

The outline of how to use the PARxCH library functions is fairly simple. First call the Open function to open the driver and initialize the sampling rate and other parameters. Once the board has been initialized, call Start to begin acquisition. Then use ReadData to move the data from the PARxCH FIFO into a PC memory array, after which it can be displayed or saved to the hard disk. Also, the Ready function can be used to determine when the PARxCH contains at least one point of acquired data. When you are done, call Stop and Close to stop acquiring data and close the driver.

CHAPTER 5: LABVIEW SUPPORT
Support for National Instruments LabView is provided in the LabView LLB VI library parxch.llb in the labview directory. This LLB contains 3 application and 20 utility VIs. The application VIs include complete data acquisition programs that rely on the underlying utility VIs which are wrappers around the corresponding core parxch.dll DLL functions supplying the low level support for all SR PARxCH software.

To use the PARxCH LLB library, put \sr\parxch\lib on your path so Windows can find the core DLL at run time. You can then access the VIs by using the File>Open menu option to open \sr\parxch\labview\parxch.llb. If it is more convenient to have those VIs available from the User Libraries button on the Function Palette, you can do this using the Edit>Edit Control & Function Palettes... menu option or by copying parxch.llb into the user.lib subdirectory of your LabView directory. For further details, please refer to file \sr\parxch\labview\readme.txt.

The PARxCH application VIs are described below. For additional information, please refer to the descriptions of the underlying DLL functions or use the Window>Show VI Info... menu option to access the information stored within each VI itself. The VIs have been saved unlocked and with their block diagrams included so that you can modify them as needed to fit your application.

APPENDIX A: ELECTRICAL SPECS
The PAR4CH uses +5vdc to power the analog and digital circuitry. Off board power of at least 10 volts is recommended for reliable operation. The system requires approximately 120ma of current. Higher sampling rates result in more current draw.

The absolute maximum analog input voltage range of the PARxCH is +/-10v. This is mapped by the on board circuitry to a 0 to 5v range that is compatible with the ADS1210 A/D converters. Although the PARxCH analog inputs are protected by resistive current limiting, do not exceed the recommended +/-10v input range, or you may damage the system. Static discharges near the analog input pins should also be avoided.

All of the PARxCH analog inputs are differential. This means that the absolute difference between the + and - inputs on any given channel must be less than 20 volts. In addition, for the system to work correctly, you must establish a common analog ground that is connected to one of the ground pins on the analog input D-shell connector.

APPENDIX B: DATA FORMATS
When programming the PARxCH, you can use the Data Format parameter, df, to choose the format of the acquired data. The two choices are signed and offset. When signed format is selected, the 24 bit data is sign extended and treated as signed 32 bit values. When offset format is selected, the data is treated as unsigned two's complement.

Note: for additional specs such as A/D resolution, please check the Burr Brown ADS1210 A/D chip specs.

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