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PicoScope can't connect if cables are connected

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PicoScope can't connect if cables are connected

Postby LouisRast » Mon Feb 02, 2015 2:33 pm

Our company recently bought a PicoScope 2204A. I successfully wrote Software to use it. But last week I found out that I can't connect to the scope if any cables (other than USB or probes) are connected to it.

    1. With a 50 Ohm BNC cable connected only to the PicoScope, the PicoScope 6 Software freezes at “Listing devices” and can only by terminated via the task manager.

    2. With a 50 Ohm BNC cable connected to the PicoScope and to a Waveform Generator putting out a signal, the PicoScope 6 Software displays a “no oscilloscope found” error message.

    3. With a 50 Ohm BNC cable connected to the PicoScope and to a Waveform Generator NOT putting out a signal, the PicoScope 6 Software works correctly.

    4. If no cable is connected to the PicoScope, the PicoScope 6 Software works correctly.

    5. If I connect the supplied probe I do not have any of the problems stated above.

The same behaviour applies to my own software (written in LabWin C).
We would like to use the PicoScope in testing equipment so the case No. 1 could easly happen if the tester forgets to plug in the cables. Even for developing it's really annoying to unplug every cable before running the software.

Is there a setting that I miss where I have to specify the impedance of the input channels?

Or did I screw over some setting in the 2204A? I always call the ps2000_close_unit() function when I close my software. However it could have happened that I shut down the unit in a non-conforming way during debugging.

Any help is appreciated


Scope information:
Model: 2204A
Driver Version: 2.1.4.17
Hardware Version: 17
PicoScope 6 Version: 6.8.8.16
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Re: PicoScope can't connect if cables are connected

Postby Hitesh » Mon Feb 02, 2015 5:53 pm

Hi Louis,

Could you please download and try the latest version of PicoScope 6 (6.10.11) from

https://www.picotech.com/downloads

If the problem still occurs after updating the software (which should have a later driver version), please could you locate the trace.xml file as shown in section 3 of the PicoScope 6 Self-Help Guide (https://www.picotech.com/download/manuals/picoscope6-self-help-guide-1.pdf) and send it to support@picotech.com

What type of USB port are you using?

You should be ok calling ps2000_close_unit(), but you can download the latest SDK from our downloads page as well or use the ps2000.dll from the new PicoScope 6 installation.

Regards,
Hitesh

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Re: PicoScope can't connect if cables are connected

Postby LouisRast » Tue Feb 03, 2015 8:03 am

Hy Hitesh

Could you please download and try the latest version of PicoScope 6 (6.10.11)
Downloading PicoScope 6.10.11 and using the latest dll seems to have resolved issue No 1. However Issue No 2 remains.

Our setup is a little special. We have multi-purpose workplaces with custom power and USB setups. In detail the setup looks as follows:
    2204A -> Powered USB2 Isolation Adapter -> Powered USB2 hub -> PC
There are about six other devices on said hub. At the moment I can’t remove the scope to connect it directly to the PC.

I’m using the Software on a Win7 64Bit System. If we decide to use the PicoScope in our testing equipment our custom C software may also have to run under WinXP 32Bit.

I made a couple more tests (with the above setup) and it looks as if the error is related to the input waveform.
    Input Signal: 0.5Vpp 1kHz Sine Wave. -> Error does not occur
    Input Signal: 4Vpp 1kHz Sine Wave. -> Error occurs 100% of the time
    Input Signal: 1Vpp 1kHz Sine Wave. -> Error occurs around 50% of the time
(I assume it depends on how high the voltage is when connecting to the Scope)

So after discovering this I repeated the same test with a DC voltage from my bench supply.
Input voltage DC:
    1V -> Error
    0.8V -> Error
    0.6V -> Error
    0.5V -> Error
    0.45V -> Error occurs around 50% of the time
    0.4V -> no Error
    0.2V -> no Error

All trace files above 0.45V input voltage show a HW Error. I also noticed that two relays in the Picoscop act differently depending on the input voltage. At >0.45V they switch in rapid succession. Below 0.45V they switch with a significant pause, one after the other. This sounded a lot like a power issue we sometimes have with other PCBs.
This made me suspicious and I wanted to verify my setup before I post here again. And I indeed found the problem. The power connector to the USB Isolation Adapter was not making contact (Since there are no power LEDs on that thing, it was not apparent). Everything works fine now.

So I assume that if the input signal rises above the 0.4V the internal relays have to switch in a different order. Because the provided power to the PicoScope was not high enough the scope threw the HW-Error.

Thanks a lot for the quick reply and the fix for problem No 1.
I still posted the entire procedure and attached the trace files. Maybe it's helpful to someone.


tl;dr
2204A Scope would not connect if on startup a signal was at the input.
On startup the relays sounded differently depending on input voltage.
InLine USB Isolator did not supply enough power (was not connected).
Attachments
0.5V DC Input_trace.xml
(4.88 KiB) Downloaded 42 times
0.4V DC Input_trace.xml
(11.52 KiB) Downloaded 43 times
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Re: PicoScope can't connect if cables are connected

Postby Hitesh » Fri Feb 06, 2015 9:53 am

Hi Louis,

Good to hear the first part is working :)

Are you saying that under the following condition that the device is not detected?

2. With a 50 Ohm BNC cable connected to the PicoScope and to a Waveform Generator putting out a signal, the PicoScope 6 Software displays a “no oscilloscope found” error message.


If so, is the PicoScope present in the Windows Device Manager when PicoScope 6 says that no oscilloscope is found?

Regards,
Hitesh

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Re: PicoScope can't connect if cables are connected

Postby berchten » Thu Apr 23, 2015 9:13 am

Dear Sirs

We have a connection problem with our "old" 3425 (Serial XFY08/023). The new SW "PicoScope® 6 - PC-Oszilloskop-Software Version: 6.10.16.2" cannot connect to the device. It is not able to recognize the device.

Computers: Toshiba Portege r600/R700 W7/64bit

We tested serveral USB cables. Shall I load the original SW (6.2.0).

Best Regards
Stefan
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Re: PicoScope can't connect if cables are connected

Postby Martyn » Thu Apr 23, 2015 12:52 pm

Please check through the following Self Help Guide

as this will resolve the majority of connection issues.
Martyn
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