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PC/104 board runs eight simultaneous A/D channels

Posted: 27 Jul 2005 ?? ?Print Version ?Bookmark and Share

Keywords:hardent Canada? pci/104? plug-in board? board? model adc?

Board offers 8 differential analog inputsBoard-level instrumentation vendor Hardent Canada has a new less-than-$1,000 16-bit PC/104 form-factor analog/digital plug-in board that touts simultaneous channel sampling capability. That's a capability that's usually found only on more costly cards.

With eight differential analog inputs capturing signals in the range of 10V, Hardent's Model ADC operates at up to 100kS/s/channel (800kS/s aggregate) at a resolution of 14 bits. Although intended primarily for industrial sensing and control applications, the ADC can also be used for simultaneous data acquisition for destructive testing, in closed-loop control, and for phase-current monitoring for vector or multi-phase motor control.

Hardent's new PC/104 board should also prove useful for making power and power-factor measurements, for vibration analysis, and for waveform analysis. It can also be used for realtime DSP applications that require precision multi-channel measurements that are phase-aligned.

In use, each input is buffered with a high input-impedance differential amplifier to help reject common-mode noise present on the units' differential inputs. Lowpass analog input filtering is also provided, using two cascaded one-pole filters.

Smart FIFO buffering
The Model ADC is also equipped with a FIFO buffer. It provides on-board storage for 1024 samples (for a maximum of 128 samples/channel). The memory is divided into two banks; while one is being written with samples the other is made available for reading via the board's PC/104 interface. When the user-selectable memory buffer threshold is reached, an interrupt to the system processor is generated and the banks are switched. In addition, the new ADC offers different sampling modes to handle different data acquisition tasks. You can select one-shot, one-shot multiple, programmable or continuous modes.

The one-shot multiple mode permits N samples to be acquired after a single trigger event. The programmable mode lets the acquisition of N samples repeat indefinitely at a user-selectable repeat interval.

Channels can also be enabled and disabled on an individual basis, and the conversion process can be triggered either by a software command or by an externally generated TTL-compatible logic signal. A similar output signal is provided for synchronization of a second ADC.

- Alex Mendelsohn

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