B&K 501A Xstr Tester W/ Digital O'scope

Thread Starter

SamR

Joined Mar 19, 2019
4,292
I am having problems transposing the "Curve Tracer Set-Up" instructions from an Analog to Digital scope. I know how to set up the X-Y mode but getting the Vertical and Horizontal calibration patterns is eluding me. The digital scope is always scanning horizontally so getting the 5 or 6 dot vertical calibration pattern is giving me problems. What I do get is this:
SDS00001.jpg
Is it even possible to use the 501A with a digital scope?
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
Nope, somehow flipping switches and twistng knobs it went back to YT. But even back in XY still having problems. Anyone who has one with a digital scope that can point me in the right direction?
 

nsaspook

Joined Aug 27, 2009
9,984
Nope, somehow flipping switches and twistng knobs it went back to YT. But even back in XY still having problems. Anyone who has one with a digital scope that can point me in the right direction?
I wish DSO's were better on X/Y but it seems that's the nature of the beast. (slow digital scan conversion display refresh with the low amplitude resolution of an 8-bit digital scope, vector display aliasing from poor software/hardware)
https://forum.allaboutcircuits.com/...ys-gabage-on-my-rigol-dso.186950/post-1733727

Professional grade DSOs are better at XY rendering.
 
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tautech

Joined Oct 8, 2019
262
Arghhh, never-mind. Scope somehow got switched back to yt mode from xy...
Try pressing the H Pos encoder to get the trigger position back in the middle of the display as it might be trying to do X-Y display with post trigger data. You haven't got a lot of processing power or fast display refresh rates in these so try to make it easy and don't expect too much. Meanwhile I'll go looking for XY examples using these cheap Siglents over at EEVblog.
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
1656856015108.png
Not sure If I understand this correctly. I am setting the scope to XY mode. Channel 1 is X, the horizontal axis and an external signal will be fed to it. So just what is "external horizontal operation" if it is NOT the X channel?

Also, I am using BNC to banana socket adapters on the scope channels since the 501A only has banana sockets. The inputs are set to 50Ω since I am using patch cables instead of probes. Also, I have daisy-chained the scope ground to both channel grounds.
 

MrChips

Joined Oct 2, 2009
26,480
View attachment 270607
Not sure If I understand this correctly. I am setting the scope to XY mode. Channel 1 is X, the horizontal axis and an external signal will be fed to it. So just what is "external horizontal operation" if it is NOT the X channel?

Also, I am using BNC to banana socket adapters on the scope channels since the 501A only has banana sockets. The inputs are set to 50Ω since I am using patch cables instead of probes. Also, I have daisy-chained the scope ground to both channel grounds.
Try disabling the 50Ω input. It could be killing your signal.
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
The service manual is B&K bk-501a User Manual (manualmachine.com)

I set up the XY mode for 1X probe @ 1MΩ even though I am using patch cables.
SDS2104X Plus_PNG_90.jpg
And set the 501's step selector to 0.2V per step. Then connected the Y-axis to the Base socket of the 501 and adjusted. Note that the graticule on my scope is limited to 8 vertical divisions where the 501 manual is for 10 divisions.
SDS2104X Plus_PNG_89.jpg
There should be 6 dots but only the top and bottom are appearing. Also they are aligned over 6 sections of the graticule. Also they are aligned from top down! Should they be aligned from bottom up (inverted)? This is going to cause problems later when the 501 scans as the display start point should be in the bottom left corner??? At this point I am simply aligning the span to the graticule and will do horizontal in the next step. Not sure why only 2 dots are appearing instead of the 6 being generated.
 

MrChips

Joined Oct 2, 2009
26,480
B&K Model 501A Curve Tracer has two outputs, V and H.
Check the output signals and voltage levels of these separately on your oscilloscope in normal Y-T mode.
 

crutschow

Joined Mar 14, 2008
30,100
but all I am using are patch cables.
At the low signal frequencies the curve tracer generates, the characteristic impedance of the cable and/or connectors has no significance, since the signal wavelength is much longer than your cable lengths.
The only thing the signal sees at low frequencies is the capacitance of the cable and the resistance of the oscilloscope input.
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
Post #1 shows it stepping. Here I simply let it auto set and it's pretty ugly...
SDS2104X Plus_PNG_92.jpg
Channel 1 is sweeping at the set voltage.
Channel 1 only on H
SDS2104X Plus_PNG_93.jpg

Channel 2 only on V
SDS2104X Plus_PNG_94.jpg
 
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Thread Starter

SamR

Joined Mar 19, 2019
4,292
Here is the XY Mode. First Channel 1 H and Channel 2 V
SDS2104X Plus_PNG_96.jpg

Then Channel 1 H and Channel 2 Base
SDS2104X Plus_PNG_97.jpg
The length of the horizontal trace is the Sweep Voltage.
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
OK, this is Channel 2 only on the Vert out. Flat line... But then it is uncalibrated and NO DUT!
SDS2104X Plus_PNG_98.jpg
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
The first step in the process is calibration. This is where my questions start. In the XY mode the "active start point" should be in the bottom left corner for NPN. OK, that should be no problem, BUT in order to do that, I will have to Invert. I will have a point that the data wants to start from, but goes in the wrong direction unless I invert it. Another small problem will be the scaling of the graticule but with the DSO I don't see that as a real problem with its Measure function. So let me start there and try and set up a calibrated screen with the active point in the bottom left.
 

Thread Starter

SamR

Joined Mar 19, 2019
4,292
OK, very strange but I Gots It! Calibrated to the bottom left inverted both X & Y.
SDS2104X Plus_PNG_99.jpg
SDS2104X Plus_PNG_100.jpg

Put a 2N2222 transistor in the holder
SDS2104X Plus_PNG_101.jpg
All it does is follow the Sweep Voltage? So I used minigrabbers in the banana sockets. And
SDS2104X Plus_PNG_102.jpg
Note that I had to turn the Invert OFF for both channels? Very Confusing... So, the insertion block needs at least cleaning... And I also checked the other input side of the tester and all good. Still need to try a PNP but all looks good!
 
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