Other Parts Discussed in Thread: PGA308
Above is the signal chain of my circuit, note the pre gain stage to the 308, and the post gain stage. I need to know how to tell the multi-cal software that these gain stages exist. Our test DUT's (that come with the multi-cal evaluation system) work great.. the percent error is excellent. On our circuit, we get percent errors that are way more then expected, (see our results to the calibration below) So we are thinking it's because the multi-cal software does not know about our pre or/andpost gain stage, and it needs to iterate it's calibration cycle to get closer, but we do not know what to do that at this point. So we are trying different things in the pre and post cal .csv files.
Our device is on channel #1 (note we changed the limits to get it to pass) On channels 6 and 7 are the test DUT's. We are thinking that because we have pre and post gain stages in the loop with the pga308, the configuration files may need to be tweaked accordingly, but we have yet to find the correct settings.
1. Pay close attention, see how we are correct in span on channel 1 but we have an offset oh 100mV? We do not know why that is.
2. Another Question I have is:
Our sensor's configuration is ratio-metric, That is, it's bridge is using Vdut as the excitation, and this is hooked to Vref of the PGA Does the multi-cal system measure Vdut during the calibration procedure?
