ni4060 2 wire resistance meauserement

[azgacat]

Hi all,

I have ni 4060 dmm and i want  to measure the resistance of a sensor in a high sampling rate.   i mean it must be almost realtime. also there must be auto range for the resistance. the sensor acts as a resistor. the other thing i need is the logging of the resistance value versus time. so any body can help me about it? i am new on using this device and labview. it should be better if you have such a code or  vi (or whatever it is) for labview 5.

thanks so,

azgacat@gmail.com

[bspears]

Hello,

Try using this example from our website:

http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E9C156A4E034080020E74861&p_...

The zip folder contains examples in LabVIEW, LabWindows/CVI, and Visual Basic.

Hope this helps!

Brian Spears

[azgacat]

Thank you very much. but i am the ni4060dmm is on the pci slot and the application didnt work. because there are some VIs missing. so the run button is broken. just you may tell me the steps to design one or if you have such kind of application i would be so happy.

many thanks

azga the cat

Message Edited by azgacat on 07-13-2005 02:31 AM

[bspears]

Hello,

You may not have all the drivers you need installed. Please ensure that you have the NI-DAQ driver and the NI-DMM drivers installed. Take a look at the screenshot attached. It shows the programming flow needed. If you have the DAQ and DMM drivers installed you should be able to load the example I gave you in the last post and delete out the SWITCH VIs (at the bottom of the block diagram that you'll open) to look like the screenshot I've attached. The DMM VIs you have may not look exactly like the ones in the screenshot because we have different versions, but they will look very similar and do the same thing.

Hope this helps!

Brian Spears

[azgacat]

Hello Thank you very much for your help. i did as you told me i have deleted the switch stuff and it works right now. but i need some optimization. here it is i will try to explain:

As I told above i have such a sensor that its resistance changes in due to the changes of some parameters. so i am trying to measure the resistance and log it to a file. thats OK up to this point. the problem starts when i use the autorange (using -1,0) the measurement gets slower.  Also there is nothing changes when i change the resolution on autorange mode. i have to use autorange because i cannot predict about the sensor resistance  value  (it may be 5k ohms or 3M ohms) due to the changes in the parameters. so if i use a fixed ranged (lets say the biggest scale) the measurements will not be so accurate, right?  so i need to do such a design that it will be so fast and so accurate. i mean as good as possible of course.

the other thing is in autoscale mode is it able to measure up to 2M ohms? these are crucial problems of my application so i would be really happy if you help. i am sending the vi file that i have edited.

[bspears]

Just some quick tips on using autoranging with the 4060. Autoranging cannot be used with an external trigger on the 4060. Therefore you cannot do synchronous scanning or handshaking with a switch. Our 4070 can do this because it is based on a different driver architecture.

Because the autorange sequentially tests various ranges of the input resistance it takes longer to settle than if the range were provided. Take a look at the little example attached below (I've attached the VI in LV 7.1 and a screenshot of the block diagram that you can recreate in LV 5). This will give a ROUGH idea of the settling time between measuremnts. I say rough because the time you probe the resistance is not synced with the loop iteration and there is no sequence expressly defined within the loop. When I probed various resistances I measured times from half a sec to 5 seconds though I didn't probe high resistances.

Yes you can autorange and measure 2MOhm.

Hope this helps!

Brian Spears