IOtech DaqBoard/3000USB Series, Руководство пользователя

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1-10 Device Overviews
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DaqBoard/3000USB Series User’s Manual
Example 4: Sampling digital inputs for every analog sample in a scan group
The scan is programmed pre-acquisition and is made up of 6 analog channels (Ch0, Ch2, Ch5, Ch11,
Ch22, Ch25) and 4 digital channels (16-bits of digital input, 3 counter inputs.) Each of the analog channels
can have a different gain and each of the counter channels can be put into a different mode (totalizing,
pulsewidth, encoder, etc.) The acquisition is triggered and the samples stream to the PC via USB2. Each
analog channel requires one microsecond of scan time therefore the scan period can be no shorter than 6 us
for this example. All of the digital channels are sampled at the start of scan and do not require additional
scanning bandwidth as long as there is at least one analog channel in the scan group. The 16-bits of digital
input are sampled for every analog sample in the scan group. This allows up to 1MHz digital input
sampling while the 1MHz analog sampling bandwidth is aggregated across many analog input channels.
The scan period can be made much longer than 6 us, up to 19 hours. The maximum scan frequency is one
divided by 6us or 166,666 Hz. Note that digital input channel sampling is not done during the “dead time”
of the scan period where no analog sampling is being done either.
If the 3 counter channels are all returning 32 bit values and the digital input channel is returning a 16 bit
value, then 18 samples are being returned to the PC every scan period, each sample being 16-bits. 32-bit
counter channels are divided into two 16-bit samples, one for the low word and the other for the high word.
If the maximum scan frequency is 166,666 Hz then the data bandwidth streaming into the PC is 3
MSamples per second. Some slower PCs may have a problem with data bandwidths greater than 6
MSamples per second.
All DaqBoard/3000USB Series devices have an onboard 1MSample buffer for acquired data.
Analog Input & Channel Expansion
Each DaqBoard/3000USB Series board has a 16-bit, 1-MHz A/D coupled with 16 single-ended, or
8 differential analog inputs. Seven software programmable ranges provide inputs from ±10V to ±100 mV
full scale. Each channel can be software-configured for a different range, as well as for single-ended or
differential bipolar input.
Adding additional analog input channels to the /3031USB and /3035USB boards is easy using J5 and J6
(two of the four on-board 40-pin headers). You can obtain male DB37 connectors for the headers by using
a CA-248 cable (1 per header).
Measurement speed of the expansion channels is the same 1 Msample/s exhibited by the primary channels.
Reference Notes :
Pinouts for all DaqBoard/3000USB on-board connectors are provided in chapter 2.