I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

SteveChen · ‎01-08-2004

I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI Sample Channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

mhaag · ‎01-09-2004

Depending on your data acquisition hardware, this is an expected artifact. It is common to see the values of unconnected inputs on the E Series boards, (and many of other devices) float between random values and at times rail at +/- 10 V. This random voltage is due to the inputs floating in a high impedance state. Any bias current or other current that is moving through the floating input will appear as a high potential on those channels. This voltage reading will usually vary from channel to channel on the E Series boards.

In order to test this, I would recommend connecting a simple voltage source (pick up any battery under 10V that you have) to one of the channels and checking the reading on a test panel in Measurement & Automation Explorer (MAX). The only tim
e we should be concerned is if at this time the reading is incorrect. If you are worried about open channels causing problems, then you can always ground your unused channels.

If you have any other questions or concerns then please let us know.

Regards,
Michael Haag
Applications Engineer
National Instruments

SteveChen · ‎01-09-2004

Thank you for your answer. I found the problem is resulted from uncorrect configuration of the hardware. I solved the problem today. Thanks again.

SteveChen · ‎01-09-2004

Right now, I generated a periodically changing pulse train at the analog output terminal. Since I want to check how many pulses are generated at the output, I need to build a subvi to count the pulses while they are generated. Which is the right way for me to do it, using analog input terminal to read it back or using counter(CTR)? Is CTR only used for digital input? Is there any existing example that I can study with?

mhaag · ‎01-09-2004

The counters will only accept digital signals as an input so you will not be able to use the counter to count the pulses. If you are interested in just creating a pulse train then I would recommend using the counters for this rather than the analog output. The counters can create a TTL, pulse train signal.

If you need to create more interesting patterns than just a pulse train then you may want to look into using a Digital I/O board instead. With an analog input board, you can use your current configuration to count the "pulses" you receive but this will need to be done in software and may not be an option if you require high speeds.

There are a number of examples for gnerating pulses and using the counter. Please refer to the LabVIEW Examp
le Finder for these.

Regards,
Michael H
National Instruments

Tsquared · ‎04-12-2004

You may be able to use the DAQ counter to count the pulses. If your pulse train has sharp edges, such as a square wave, and signal levels are compatible with TTL, then you should be able to use the counter. If your voltage levels are above 5V, then you can use a simply voltage divider to bring the voltage down at the counter input. But be careful, I think the counter input max voltage is about 5.5V.

ryan_utas · ‎09-01-2008

Hi. I am using the NI USB-6212 and I was having the same issue as well.

I've tried one of the solutions which was ground all unused channels and it did solve my problem. But I was wondering if there is a more elegant way to solve this issue rather than having 12 colorful wires (15 Analog Input, I'm using 3/15) bunched up into the AI GND?

Thank you

Ryan

Steve_B · ‎09-02-2008

Hi Ryan,

Grounding your channels will ensure that your signal is not floating above or below your ground reference. You can choose which channels to include in your task to avoid the open channels if that is a possibility for your application. Including the 3 channels you need into your task and not measuring the rest of the channels would work around the issue.

Incorrect Readings when Scanning Unconnected or Open Channels
http://digital.ni.com/public.nsf/websearch/4E9B8B3F8FD3A31B862562B5004EA1D9?OpenDocument

Steve B

rangga_39a · ‎01-28-2009

Dear National Instruments Engineer..

i want to plot the 3 phase phasor diagram, acquired from NI-DAQ 6008 which connected to 3 phase voltage source..

How to measure the phase angle of each voltage (relative to other phase)?

what should i do with the dynamic data wire? should i convert it to array? or other specific data type?

can you guys help me? please...

voltage and current signals · ‎09-27-2010

i am trying to acquire voltage and current value from analog input AI0 and AI1 sample channels.

but why does the DAQ read both de current and voltage values all the same?

Dynamic Signal Acquisition

I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ. I am trying to acquire voltage value from analog input using AI sample channel.vi. Why does the DAQ read 10 all the time even though there is no input connected at the analog input terminal?

Re: I am a new user of DAQ.

I am a new user of DAQ.