07-19-2010 12:31 PM
I have a USB-6008 DAQ that has one of the 2 AO's stuck on at 1 Volt output. The other channel works great, but the other is unresponsive to all DAQ assistant commands and the NI hardware diagnostic. All it does is output 1 volt.
I have my suspicisions that the AO was overloaded with respect to its current output. Do these have short-circuit protection? Anyone have any idea why it outputs 1 volt no matter what I do?
I have reset and shutdown multiple times.
-KLK
07-20-2010 03:48 AM
Hi KLK
After looking at the manual online it is evident that in order for the 6008 to operate it needs 0-5V to be supplied to it. Any more and the outputs will simply pull to ground. This should be checked.
Another thing that could resolve this issue is if you use the DAQ Assistant to check that each of your AO's have a signal output range of 5. (See the attachment below). This will check that the outputs are in the correct range.
Should this fail I suggest contacting your local NI Branch as there is a chance that there could be a fault with your USB-6008.
07-20-2010 09:37 AM
What do you mean it needs 0-5V supplied to it? For voltage output from the DAQ, doesnt that supply come via USB? I'd just like to clarify that the output will not go to zero volts, it is stuck on 1Volt and will not vary no matter what control I attempt to change for that particular channel. As soon as i plug it in it is stuck on 1 volt and it never changes. I'm pretty sure the hardware has a fault.
@MikeParkin wrote:Hi KLK
After looking at the manual online it is evident that in order for the 6008 to operate it needs 0-5V to be supplied to it. Any more and the outputs will simply pull to ground. This should be checked.
07-20-2010 10:09 AM
Hi KLK,
As you mentioned in a previous post, it might have something to do with the current you are drawing from the output.
Can I ask what this value is? If you are drawing more than 0.6mA this could go some way to finding the problem.
07-20-2010 11:09 AM
From what we can tell from testing, we should have been only drawing 4.8mA from the output. I believe they are rated for 5mA.
07-20-2010 11:20 AM - edited 07-20-2010 11:22 AM
Output current drive is 5mA according to the spec sheet. 4.8mA is pushing it a bit, but it should not break the device. I would send the device back for replacement. Beware, you may have a spike that draws more than 5mA. Try backing down on the current drain or make very sure that there are not spikes when you turn the output on.
Analog Output
Analog outputs........................................2
Output resolution ....................................12 bits
Maximum update rate .............................150 Hz, software-timed
Output range ...........................................0 to +5 V
Output impedance...................................50
ΩOutput current drive................................5 mA
Power-on state ........................................0 V
Slew rate .................................................1 V/
Short circuit current ................................50 mA
Absolute accuracy (no load) ...................7 mV typical,
36.4 mV maximum at full scale
μs
07-20-2010 11:24 AM
The problem could be that the external connection is sinking too much current from the source. This means that the output can only source 0.6mA.
To avoid this problem a pull-up resistor could be added to the configuration. This will allow the device to source 8.5mA.
I hope this helps you.
07-20-2010 11:36 AM
@MikeParkin wrote:
The problem could be that the external connection is sinking too much current from the source. This means that the output can only source 0.6mA.
The spec says the output can drive 5mA.
Output current drive................................5 mA
This means that the output is not an open collector, and it should not need a pull up resistor. If the spec says that it sinks current, then it can be open collector. The key word here is "drive".
07-20-2010 11:36 AM - edited 07-20-2010 11:37 AM
MikeParkin wrote:
The problem could be that the external connection is sinking too much current from the source. This means that the output can only source 0.6mA.
The spec says the output can drive 5mA.
Output current drive................................5 mA
This means that the output is not an open collector, and it should not need a pull up resistor. If the spec says that it sinks current, then it can be open collector. The key word here is "drive".
I must have hit the post button twice. Sorry.
07-20-2010 12:41 PM
tbob:
Posting twice will not get the output drive up to 10mA 🙂
-AK2DM