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DI-145 Data Acquisition Starter Kit Developer's Diary

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1/10/2011 Note #9 More testing and Revision C

The firmware bug that prevented analog input channel four from operating has been found and killed. All four analog input channels in the DI-145 data acquisition starter kit are now operational. Pull-up resistors have been added to the two digital input channels and the analog inputs have been tested to the ±240 VDC or peak AC spec and found to survive. However, a funny thing happened along the way … the input connector is specced for 300 VDC or peak AC operation (or, ±150 V). So, although the circuit will tolerate 240V, the connector will not (at least in theory). The specification noted on the data sheet will change to reflect this.

In addition to pull-up resistors being added to the digital inputs, we also added two capacitors per analog input channel to provide anti-alias filtering. These throttled the frequency response of the analog channels to -3db at 100 Hz, rolling off at -20db per decade.

All the changes described above were tacked onto the revision B board, tested, and verified. Next, we’ll order engineering prototypes of the revision C board that reflects these changes. Those should be available on or around January 24, when testing will resume with this (hopefully) final version of the hardware.

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