PCSGU250: erroneous behaviour

Instruments PC Oscilloscopes and Recorders
1

Hi,

I got the PCSGU250 last fall as a present. Hadnt’t put it into service yet until last weekend
when I wanted to do some analysis of several tube audio amps.

I installed PcLab2000LT version 1.10, installed the USB device driver from
Microchip V. 1.0.0.2, dated 24.08.2009.

added info: firmware is V 1.01

First, I did the install on an XP Pro Notebook. As this showed erroneous behaviour,
I did another install on a Win-7 Notebook, similar erroneous behaviour.

Both Notebooks have the latest MS updates installed.

I’ve also read the various posts and feedback in this forum and think I’ve followed
all recommendations given.

Yet, the scope freezes after a short while (waiting for a trigger) and in addition
shows some strange wave forms, like clipping sinus wave forms towards the second
line from the bottom.

In addition, there is no trigger detected plus the vertical (Y) readings are erroneous
(e.g. showing different readings for 1 Volt and 0.3 Volt settings for the same input).

I made these tests with the scope directly connected to the generator via the probe.

I’ve checked the probe and swapped the probe, it is ok.

The generator seems to be ok. I’ve checked this with my other scope, a 100MHz 1GSa/s
DSO.

Any additional idea what to do, or is it just a hardware problem?

klausb

2

Just trying to get some pictures here…

2 screen shots, same level and frequ. of signal from the Gen.

#1 with Y input sensitivity at 1 Volt, signal @ 0.56V PP

#2 with Y input sensitivity at 0.3 volts, signal @ 0.047V PP, a flat line.

And look at the CH2 numbers! CH2 was OFF during the measurement.

Looks strange to me.

1032×633

1032×633

3

Most probably the oscilloscope is defective.

Are there similar problems with channel CH2 too?
Have you tried to use the original driver for Windows XP. The driver is in the CD folder \PCSGU250Driver. The driver version is 1.0.0.6.

[quote]And look at the CH2 numbers! CH2 was OFF during the measurement.[/quote]The measurement is active even if the trace display is off.

4

I’ll try with the driver version that came with the unit and report back.

First screen shot:

CH2 was left open, no connection. You can see about a 10% cross talk on CH2
from CH1. Is that ‘normal’?

Second screen shot from above:

the point is that the CH2 readings (PP and RMS voltage) now are exactly 2x of
what is displayed for CH1.

CH1 was connected to the Gen via the probe.

CH2 was open, nothing connected there! But a 2x voltage reading relative to CH1.

klausb

5

[quote]CH2 was left open, no connection. You can see about a 10% cross talk on CH2
from CH1. Is that ‘normal’?[/quote]The low values displayed on the screen may be CH2 noise, no crosstalk.
Here is an example screenshot what you should see on the screen with the settings you had:

800×475

The CH2 is left open in this case.

6

Your screen shot looks pretty ok!

I wish mine would look the same way…

Ok, here are the findings of today:

Driver 1.0.0.6 shows the same results as 1.0.0.2 on my XP Notebook.
Before and after a session I checked the installed driver version through
Windows device manager.

Behaviour on CH1 and CH2 is the same.

Scope hangs-up after several Autosets (after having changed Gen
frequency).

0.3 V sensitivity readings are totally way-out (muuuuch too low) on both channels
(see my earlier post with the 2 screen shots).

Waveform distortion if shifted towards the display bottom (clipping of negative
sinewave parts). Moving the waveform to the top of the display area keeps the
shape ok.

Initial overshoot with rectangular waveforms (each cycle), between 20 to 40%,
which is a lie, as I checked the Gen signal with my 100MHz DSO and the waveform is
perfectly ok (shape, frequency and voltage).

From that I’d guess there is something wrong with the hardware.
The Scope is still in the warranty period so I will call the company where it was
bought and ask for an exchange.

Thanks so far.

klausb

7

Based on all the indications, it seems the scope is defective.

8

@VEL255,

I phoned the reseller this afternoon and per their instructions sent back
the PCSGU250 to them today, including the failure description.

Looking foreward to receiving a working unit soon.

In general, this device is exactly what I was looking for, especially the
Bode function.

Will update here as soon as the replacement has arrived and after I have
put that into a test round.

Thanks again for your support.

klausb

9

Hello VEL255,

Today the parcel with the replacement PCSGU250 arrived from
Voelkner in Nuernberg (Germany).

I had taken the parcel with the defective scope to the mail shop on
Thursday, 28-July-2011, late afternoon. So I guess it was shipped
from there on Friday morning.

So the total turn-around time was 6 calender days, including shipping
and including the weekend.

That’s pretty fast! Thumbs up and thank you Voelkner! :slight_smile:

After unpacking (the replacement scope was a new scope) I put
the scope through a brief test and everything now looks as it should
(using driver V. 1.0.0.6, which was still installed on my XP Notebook).

Excellent!

Thanks again VEL255 for your guidance!

klausb

(now a happy user)

10

I’m happy to see that you got the PCSGU250 replaced and you like it !