Re: BC-140 fast ADC problem

charlie thibault (cth@bruker.com)
Tue, 19 Oct 93 12:14:39 EDT

According to J\vrgen Tegenfeldt:
>
> I have an MSL system with a Bruker BC-140 fast ADC (2x20MHz according to
> Bruker). For certain experiments I would like to sample a signal as fast as
> possible. Now, DISNMR on the ASPECT does not agree to set SW to more than 5
> MHz although I have told the system during installation that I have this
> particular ADC, so apparently there must be a SW-limit set inside DISNMR
> that is lower than that allowed by the ADC. Has anybody else run into this
> problem, and, above all, does anybody know about a way to bypass the problem?

I vaguely remember when I implemented the BC-140 in DISMSL (about 6 years
ago) that there was a reason for not allowing a sweep widths > 5MHz
but I can't remember what it was :^( In any case the software won't
let you set the SW >5MHz _unless_ XA is set. So here is the workaround:
Either use a pulse sequence designed for external address advance
like the one below and set the dwell mode to XA (just type XA) _then_
set the SW to the desired value the dwell will be set automaticly.
I haven't tried this but it should work.

; VERYFAST.PC
; SIMPLE ONEPULSE ACQUISITION USING EXTERNAL ADDRESS ADVANCE OF DIGITIZER

START, D1 [F1 PLS^] ; OBSERVE PULSE
D3 [STA] ; RING-DOWN DELAY
LOOP TD TIMES ; ACQUISITION LOOP
(DW/2)[XAD] ; TAKE POINT
(DW/2)
END LOOP
(D0-AQ) ; RECYCLE DELAY
GOTO START

; SET NT AND XA

-- 
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       ...     ...	Charles G. Thibault
      .    * .    .	Manager of Software Development
       .   . .   .	Bruker Instruments Inc.
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