Re: Tek 576 Curve Tracer USB port to a cpu ... ?


A few observations. You can pick off the horizontal and vertical analog
bipolar voltages on the Display Sensitivity Switching board - diagram 5 in
the manual. The same nodes are also available on the Display Amplifier
board diagram 9. These nodes represent the voltage signals taken across the
sensing resistors and they are before the amplification stages - the latter
of which also have the calibration pots.

Unfortunately, those nodes are not readily available - the display
switching board is buried under another board, and the display amplifier
board has power resistors in the way of those nodes. It's probably easier
to get to the former. I saw a youtube video of a 546 owner who took the
board out - which may not be necessary for us.

Since the voltage is true bipolar, one would need a differential ADC like
the ADS7808P 12-Bit device. That digital signal can then be sent to an
arduino and passed through the USB port to by processed by Python or
whatever or whatever SW you're into.

Linear scaling of the XY data would be needed to initially "calibrate" the
data to the 546 - which is simple. Some of the display controls on the 546
would need to be offered on the GUI - to essentially tell the program what
you are measuring e.g., what is being measured (e,g., Ic vs Vce) and the
corresponding units - so when you change scale on the 576 for example, you
would click a radio button on the GUI accordingly. Some things may be able
to be derived from the data, so PNP and NPN may be distinguishable with
knowing other inputs like Ic vs Vce on the corresponding axis.

If plotting XY data using MatLib, which is what I suggested earlier, the
data is scaled automatically by the Matlib program, and the display is
updated - but you still need to inform the program via the GUI so that the
labels can be changed accordingly.

This all sounds interesting, fun to implement, and very doable but I'm not
sure of its value. It's not a weekend project - it's more like weeks. And,
with inevitable feature creep, it could be a few months!

There's also the issue of wear and tear on our 546s during development. I
added many miles onto my CNC machine when developing my PCB auto driller

John Justin

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