User`s guide

Universal Library User's Guide Analog Input Boards - USB-2500 Series
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DIGITAL16: FIRSTPORTA (FIRSTPORTB must be configured as an output)
Rate ANALOG: Up to 1 MHz
DIGITAL16: Up to 12 MHz (system-dependent) if no analog channel is
selected. Otherwise up to 1 MHz.
Range Ignored
Hardware considerations
Associating CJC channels with TC channels
The TC channels must immediately follow their associated CJC channels in the channel array. For accurate
thermocouple readings, associate CJC0 with TC0, CJC1 with TC1 and TC2, and CJC2 with TC3.
The board must be configured for differential inputs when using thermocouples
TC inputs are supported by differential mode configuration only.
Channel count
For input and output scans, the count must be set to an integer multiple of the number of channels or a
BADCOUNT error is returned.
Sampling and update rates
Sampling and update rates are system-dependent. Data overruns/underruns may occur with higher sampling
rates when using BACKGROUND and CONTINUOUS modes. To avoid this, use a larger buffer/count size, or use
NONSTREAMEDIO mode, if supported. The minimum size buffer is 256 for cbAOutScan(). Values less than that
result in a BADBUFFERSIZE error.
Settling time
For most applications, settling time should be left at the default value of 1 µs. However, if you are scanning
multiple channels and one or more channels are connected to a high impedance source, you may get better
results by increasing the settling time. Keep in mind that increasing the settling time reduces the maximum
acquisition rate. You can set the time between A/D conversions with the ADC Settling Time option in
InstaCal. Select between 1 µs, 5 µs, 10 µs, or 1 ms.
Setpoints
You enable setpoints with the SETPOINT_ENABLE flag. This flag must be OR'ed with the ChanTypeArray
argument values. You set the setpoint criteria with cbDaqSetSetpoints()/DaqSetSetpoints(). The number
of channels set with the SETPOINT_ENABLE flag must match the number of setpoints set by the SetpointCount
argument (cbDaqSetSetpoints()/DaqSetSetpoints()).
Output non-streamed data to a DAC output channel
With NONSTREAMEDIO mode, you can output non-streamed data to a specific DAC output channel. The
aggregate size of the data output buffer must be less than or equal to the size of the internal data output FIFO
in the device. The FIFO holds 524288 samples. This allows the data output buffer to be loaded into the
device's internal output FIFO. Once the sample updates are transferred or downloaded to the device, the
device is responsible for outputting the data. You can't change the output buffer once the output begins.
Trigger DAC output operations with the ADC clock
Specify the ADCCLOCKTRIG option to trigger a data output operation upon the start of the ADC clock.