ADLINK Technology NuDAQ PCI-9812/10 User Manual

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ADLINK Technology NuDAQ PCI-9812/10 User Manual Manual pdf 44 page image

36 • Operation Theorem5.5.7 SummarySo far we have discussed the AD data transferring, the maximumsampling rate and the maximum continuous data length at thesample time. Here we summarize to get the following steps:1. caculate the total data throughput;2. check if the total data throughput is higher than the effective PCIbandwidth in your system;3. if it is higher, then the maximum data length will be limited to16K samples for 2 channels and 8K samples for 4 channels;4. If it is lower, then the maximum total data size is 64M byteswhich comes from the limitation of host memory;5. For continuously acquiring the AD data, that is, the data lengthis infinite, you can use the “double-buffered” software. However,you still need to calculate the CPU computation bandwidth tocheck if the continuity is possible.5.6 AD Data FormatThe A/D data of 12-bit PCI-9812 is on the 12 MSB of the 16-bit A/Ddata. The 4 LSB of the 16-bit A/D data must be truncated bysoftware (please refer to section 6.2.3). The relationship betweenthe real signal voltage and the sampled value is shown in thefollowing table:A/D Data (Hex) Decimal Value V (Volts, -1V~1V) V (Volts, -5V~5V)7FF 0 +32752 +1.0000 +5.0000400 0 +16384 +0.5002 +2.5010001 0 +16 +0.0005 +0.0025000 0 0 0.0000 0.0000FFF 0 -16 0.0005 -0.0025C00 0 -16384 -0.5002 -2.5010801 0 -32752 -1.0000 -5.0000800 0 -32768 -1.0049 -5.0024The A/D data of 10-bit PCI-9810 is on the 10 MSB of the A/D data.The 6 LSB of the 16-bit A/D data must be truncated by software.The relationship between the real signal voltage and the sampledvalue is shown in the following table: