Test and Measurement Forum

When I run Picoscope on my HP 1.2 Ghz Pavillon Laptop (XP home) there is a periodic 3 second glitch which looks like a reset.
I can hear a relay going inside the unit. On my desktop everything is ok.

Strange problem this, it may be that the unit (which unit is it?) is filling up with data more quickly than you would like it to (we should be able to work around it if this is the problem).

In the Settings | Options menu, click on Advanced and let me know what the 'Maximum Samples per Scope trace' is set at ... tell me the timebase per division you are using and whether the LED goes out when the glitch occurs. Send a PSD file of the glitch to tech@picotech.com if its visible.

Also if you have the voltage range set to 'Auto', try setting it to a fixed value, then listen to see if the relay still clicks every 3 seconds.

What parallel port mode do you have set in the BIOS?

Let me know how you get on with this.

Best Regards,

Hi

I seem to have a similar problem...

Using an ADC216 on an AMD 1700 powered desktop, displaying a constant DC signal on 2 channels, periodically the trace 'glitches' and the display fills with noise at +/- 20v .

Version 5.09 of picoscope is running at 1 mS/div, DC, all settings and options set to default.

The glitches occur at about 10 to 30 second intervals, and if you listen carefully you can hear a metallic click inside the unit. When the unit is working OK, the red light flashes about twice per second; Just prior to the glitch being seen on the screen, the red light stops flashing, and the glitch occurs just as the flashing re-commences.

I first noticed this problem when running the unit with some software I have been writing to use the unit as an X-Y plotter, but it only seems to happen when running in block mode. Using get_single it seems to be OK.

Any ideas?
Ian

Hello again...

I seem to have fixed my problem... after connecting the 'scope to my laptop - where it worked fine - I investigated the PC a bit - and remembered that I normally have a scanner plugged into the parrellel port.

The scanner software was still active and appears to be polling the parrellel port every so often, presumably to see iff the scanner is hooked up. I guess that this is upsetting the ADC.

If I turn the scanner s/w off, everything works OK. I wonder if this will help Steve?

Ian

I have an El`Cheepo laptop with a glitch every so often that fills the whole voltage scale! I have found that every so often, the harddrive does something in the back ground for no apparent reason. Some silly windows thing. It must be moving some data for a half second burst. The glitch in the screen will happen at exactly the same time as the hard-drive bowel movement.

Also, at very low voltages such as 20mV Pk-pk, the EMI/RFI/ripple from my cruddy laptop power supply will intrude upon the signal as common mode noise. I simply run on the battery when I take small signal measurments.

Thanks for the tip Rich,

I'm sure this thread will help quite a few users with noise problems. Another possible way of countering noise on laptops is to connect an earth point (if you have the luxury of an earthing screw on the back of your laptop!)

Regards,