Max Square Wave Latency

[Fred]

Yes! :-)

1) Verify latency with 10k/10k/1nF input setup and 5V square wave signal on VR+ with VR- floating
2) Verify reduced latency with capacitor removed and same setup
3) Fix VR- @ 2.5V and measure latency
4) Still fixed @ 2.5V, reinstall cap and measure latency
5) Still fixed @ 2.5V with cap, reduce resistance from 10k to 1k and measure latency

I can't think of more things to try with it than that, but if you can, feel free to play around more! :-)

Fred.

[Dan]

No probs! Will do ASAP!

Just ordered a Saleae Logic16! (3-5 days delivery)

Will keep you posted!

[Fred]

Those are cool, and quite big! :-) I look forward to seeing pretty photos of your bench + it.

[Dan]

sweet! glad I made a "good" choice then. The Open one you told me about just looked a little tacky. . . . LOL

[Fred]

Yes, we've all seen your valve cover ;-)

What we haven't all seen is the car that your Mrs has! :-o

[Fred]

Another thing to try is watch the floating negative pin with the second channel of a scope and see what it's doing. I have a hunch that even without the cap it is moving around a lot. Hence the suggestion of fixing it at 2.5V and watching the latency then.

[Dan]

my Logic16 just arrived

testing to follow soon!

[Fred]

While you're at it, how about testing 1k instead of 10k for the input resistors, with std cap and floating -ve, i bet it's still bad. Prove me wrong :-)

[Dan]

My Test Results in the form of traces from my Logic16 are as follows, in order of tests requested.

1) Verify latency with 10k/10k/1nF input setup and 5V square wave signal on VR+ with VR- floating



2) Verify reduced latency with capacitor removed and same setup



3) Fix VR- @ 2.5V and measure latency



4) Still fixed @ 2.5V, reinstall cap and measure latency



5) Still fixed @ 2.5V with cap, reduce resistance from 10k to 1k and measure latency



and a new item,

6) With cap and two 10k resistors, feed square wave into VR+ and same inverted square wave into VR-

[Dan]

Just to be picky, I will also throw up some LA traces with actual latency measurements.

2) Verify reduced latency with capacitor removed and same setup - with actual lag time



3) Fix VR- @ 2.5V and measure latency - with actual lag time



4) Still fixed @ 2.5V, reinstall cap and measure latency - with actual lag time



5) Still fixed @ 2.5V with cap, reduce resistance from 10k to 1k and measure latency - with actual lag time



6) With cap and two 10k resistors, feed square wave into VR+ and same inverted square wave into VR- - with actual lag time