Other Parts Discussed in Thread: PGA460
Tool/software:
Hi Team,
I am trying to mask the burst of the transducer for the first 800uS and this works if I set the first time threshold to 800uS and the level to 248 with a +7 offset. However if I set the first 8 time thresholds to 100uS and their levels to 248 with the +7 offset I am getting echo times less than 800uS.
I am trying to get operation using the digital long gain as soon as possible by setting all the time thresholds to 100uS but the blanking doesn't work then. Am I doing something wrong here?
A second issue I am having is due to a spike occurring when the PGA460 switches from the digital short to digital long gain. Even if the settings are identical on both, the signal as seen on the data dump jumps up at this point. If anything I would expect the signal to fall as when it switches to the long digital gain it is subtracting a noise level value of 31 prior to digital amplification which it is not doing when using the short digital gain. Can you explain why this is happening? The datasheet describes how the threshold is automatically adjusted if the gains are different to prevent false triggering - if the long gain is 3 and the short gain is 2 does it increase by 3/2 = 1.5? What happens if the result is greater than 255? In my case the short and long gains are the same so the threshold isn't adjusted and the spike I am getting at the transition is giving me a false echo at this point.
Best Regards
Keith
