UE9 not detected after unplugged | LabJack

UE9 not detected after unplugged

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francoisbiar's picture
UE9 not detected after unplugged


I'm writing a python program which uses the UE9 streaming functions, and when my program crashes and I can't access the device, I may unplug and plug the USB port again to get the access back. But since yesterday, I completely lost the access of my device...

Before that, I had the power-up LED behavior as described in https://labjack.com/support/datasheets/ue9/hardware-description/leds , but now when I plug it, using any PC or the power supply, the COMM led stays desperately off, as seen on attached file. Now I get the labjack not found error everytime i try to open the device in python.

Here's a piece of the code I typically use in my program, the one that "broke" my device:

import ue9
from Queue import Queue
handle = ue9.UE9()
handle.streamConfig(NumChannels=2, ChannelNumbers=[0, 1], ScanFrequency=25000)
queue = Queue()

while True:
data = handle.streamData().next()

Typically, when an exception occurs, it happens that the streamStop() call does not work properly, so the streaming is still on but my program is terminated. The fastest way I found to reset the device was then to unplug and plug it again.

I tried the ethernet connection, and it doesn't work either. I'm using Ubuntu 16.04, and v1.11 firmware. Any ideas for me ? 

Regards, François

File Attachment: 
LabJack Support
LabJack Support's picture
Un-plugging the device to

Un-plugging the device to reset it and terminate your program is acceptable behavior when streamStop doesn't work.  I highly doubt the code you wrote broke the device.  ESD or some other form of electrical shock from your computer or what you are sensing is likely the cause of your LED issue.

It looks like some sort of shock was delivered to the UE9s COMM processor and it is no longer working properly.  A few quick things you can do before following the RMA route is to plug the device into your computer and check the voltage between VS and GND using a DMM.  The voltage should be ~5V (4.5-5V).  You can also disconnect the UE9 from the computer and measure the resistance between VS and GND, the resistance should be something close to 55k ohms.  

The RMA process is described on the about/returns page.  If you want to send it back to us to have us look at the device feel free to follow the steps outlined on that page and we will approve your RMA.

LabJack Support
LabJack Support's picture
Do further testing with

Do further testing with nothing connected to the UE9 except the USB cable.  Also, try powering up with the power supply rather than USB cable to see if you get any COMM LED activity.

So you are not getting any COMM LED activity at all?  You can try powering up with a jumper securely installed from FIO0 to SCL, or from FIO1 to SCL, but at this point is seems that your COMM chip or its power supply might have been damaged.


Try a different computer to see if you can get an COMM LED activity.

You can use a DMM to do some initial checks for hardware damage.  Clamp the negative lead securely into a GND terminal, and the check voltages (or resistance) with the positive lead.  If testing at a screw terminal note that the probe or wire must be securely clamped inside the screw terminal ... you can't just touch the screw head.

Voltage measurements are done with just the power supply connected (USB or Vext).  Nothing else except DMM.

Resistance measurements are done with nothing connected except DMM.  The UE9 should be unpowered.  All power rails typically show a resistance >50 kohms.

Checking the voltage and resistance of various power rails is the first step.  The main one to check is VS, but a complete list is:

VS (any screw terminal, ~5 volts)
Vusb (pin 6 of U17, ~5 volts)
Vext (pin 8 of U17, ~5 volts)
3.3Vcontrol (pin 5 of U14)
3.3Vcomm (pin 5 of U15)
2.5Vcomm (pin 4 of U16, C145 is best place to measure)

francoisbiar's picture
I tried all of the above: I

I tried all of the above: I tried the jumper, I plugged the power supply or to another computer doesn't work either, and every voltage listed is OK. So I'll initiate a return. Thanks for your reply.

LabJack Support
LabJack Support's picture
Sounds good.  Let us know if

Sounds good.  Let us know if you have issues initiating a return.