Surf PI follow-up super results.....

[plumabob]

Hi Don,

I have a scope but I'm not sure how to how it up to show the delay. If you would be so kind to explain that I would appreciate it. I can then post my results.

Bob

[dfbowers]

Hi Don,

I have a scope but I'm not sure how to how it up to show the delay. If you would be so kind to explain that I would appreciate it. I can then post my results.

Bob

Hi Bob,

Do you have a dual trace scope? You can monitor TP1 and TP2. One will be the output of the preamp and the other will be the delay pulse. You can measure the delay from the beginning of the pulse from the preamp to the fallling edge of the delay pulse. Adjusting your delay pot will shorten or lengthen your delay pulse.

The falling edge if the delay pulse will be somewhere on the decay curve. This should be your delay. Your decay curve will most likely have a flat spot on top, caused by the diodes clipping the flyback signal. If you can decrease your delay until it hits the flat spot on your preamp signal, your detector will stop resonding. This is your minimum delay setting.

Now if you DON'T have a dual trace scope, you can take advantage of the imperfections in the design. Look very closely to the output of the preamp and you will see as small blip in the decay curve that changes with adjusting your delay. That will coincide with the falling edge of your delay signal (neat huh!?).

I'm not near my scope this week, so I cannot post any images.

Hope this helps.

Don

[TH Jim]

Hi Don and all,

Yes I totally agree we need to control as many variables as possible to produce meaningfull comparisons. I'm using a 15K in series with a 100K pot for my delay control the same as on Apberg's long board and I have my delay set on or near minimum to get the best depth. I don't have a scope at the moment (only winscope for the PC soundcard) but I'm looking for one to buy ASAP.

I thought it my be a good idea if we had another forum here at geotech that was soley for posting test results, that way anyone who builds a machine can easily reference what results others have achieved and what they should expect from their own build. It would also be usefull to direct the newbies who frequently post the question of "what is the best machine to build" to the test results forum.

Anyone else interested?