Digital VacuTrace

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hagtech

Digital VacuTrace
« on: 19 Aug 2003, 07:55 pm »
The circuitry inside a VacuTrace is entirely analog.  In hindsight, this was a most difficult approach.  Would have been much easier to use a PIC or some other microcontroller.  The side benefit would have been a serial port to read out digital data to a PC.  That would have been cool.  Oh well.

The common way to get "digitized" curves is to take pictures of the oscilloscope display with a digital camera.  Although this works quite well, it still does not capture the raw XY numerical data.

Some digital scopes work fine (must have XY capability) and can be read by a PC.  They are costly.  I recently discovered this PC-based digital scope that will work :!: It is cheap, and most importantly, it samples both channels simultaneously.  The problem with 99% of this type of scope is that they alternately sample channels - and that leads to skew and errors.

Here's info on the $189 USB scope for VacuTrace:

http://www.usb-instruments.com/hardware-ds2200.html

It can be purchased in the US at http://www.saelig.com.  I plan on buying one of these soon, hopefully in time for VSAC.  

jh :)

hagtech

Bought one!
« Reply #1 on: 8 Sep 2003, 06:01 am »
Hey, this USB scope works pretty darn well.  I like it almost as much as the analog scope.  Only drawback is that the alternate trace is not dotted.

Very easy to use this "virtual" scope.  Operation is fast, very much a real-time feel.  Image below shows program in operation.  VacuTrace is testing a 12AU7 in A/B mode (both sections at same time).  This particular tube was a reject - for me anyway.  It met specifications; being quiet, had very well behaved curves, good transcondutance, rp, etc.  Just that it was not particularly well matched between sections.  This tube hit the trash bin because it is not good enough to go into a Trumpet.



Nice pear of gear for $189.  Also has a very useful FFT feature.  

jh :)