Ni 3214 strain measurements

I am currently trying to create a LabVIEW program for the night 3214 that measures and detects strain placed on an object for my senior design project. The order has been placed for the node and while my group waits for it to arrive we are trying to set up the code using the simulated components provided in the LabVIEW wsn module. using the example program provided in the manual for the node I have questions on how to set up a data base for logging data, as well as how to set strain limits for the node so that the warning system will go off.
Thanks in advance

Westbury,
I would suggest posting this to the Wireless Sensor Networks forum over at http://forums.ni.com/t5/Wireless-Sensor-Networks/bd-p/430
The people who view that forum are much more likely to be able to help.
Matt J
Professional Googler and Kudo Addict
National Instruments

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Strain measurement using 9237 and cDAQ 9172

I am trying to measure strain using a 9237 and cDAQ 9172.
The strain gage is connected to 9945 (Red wire to EX+, White to IN+ and Black to QTR terminal also tried connected the white and black to IN+ terminal).
The 9945 is connected to 9237 quarter bridge strain measurement module on a cDAQ 9172. I have two 9237 on the cDAQ 9172.
The device passes the test in MAX.
The problem is I cannot read the strain value.
Can anyone help me please?
Attachments:
Strain measure.vi ‏19 KB

Hi jujare,
In the VI you attached, you don't have the bridge configuration set up. The default is full bridge I, so if you have a quarter or half bridge wired up, that is one reason you could be getting bad data. I'd suggest you take a look at "Cont Acq Strain Samples(With Calibration)-NI 9237.VI" in the Example Finder. It shows the configuration for bridge type and has some handy wiring diagrams. You could also add controls to your vi to set the bridge configuration if you'd prefer.
If your strain gauge only has three wires, it's probably a half or quarter bridge. A full bridge needs at least four wires.
I hope this helps!
Regards,

Configuring NI9219 for strain measurement

Hi!
I am trying to set-up a strain measurement VI using Labview. I am using NI 9219 module on NI cDAQ 9172 chassis. My strain gage is configured in a quarter-bridge arrangement and I have made strain gage connection accordingly (to terminals 3 & 5 in NI 9219). However, I do not understand what are TEDS terminals for and what to connect to those terminals. Can I use virtual TEDS for this? I couldn't find a virtual TEDS for NI 9219. Any information in resolving this issue would be highly appreciated.
Best,
Nyquist99
Solved!
Go to Solution.

Hi, the TEDS terminals are only for transducers, like a strain gauge, that support TEDS (Transducer Electronic Data Sheet). The TEDS standard is just the ability of a transducer to save information about itself in internal memory. This information includes things like calibration constants and dates, scaling factors, electrical characteristics, etc. It is stored in a standard template which can be read by computers and DAQ cards via those TEDS lines. For you application, you should just leave them unwired, and setup up your strain gauge normally.
Chris Bakker
National Instruments
Applications Engineer
Check out LabVIEW 2009 and the New X-series DAQ!

Load cells and non contact strain measurement

I am designing a bi-axial machine which meant for a fatigue test.
Could someone recommend me where to get a dynamic load cells and as well non-contact strain measurement?
Thanks.

Hi Alvin788,
Do you presently use any hardware to measure these or are you enquiring as to what hardware/software you will need? Are you planning to use LabVIEW? The following three links talk about measuring Load Cells as well as Strain Gauges
Continuous Acquisition from a Smart TEDS Load Cell Sensor
How do I Configure a Load Cell in MAX?
Strain Measurement with a Strain Gauge
This post will also be highly helpful.

Strain measurements using labview and DL750 scopecorder

Hi
I want to use labview to do strain measurements using DL750 Yokogawa Scopecorder. I have installed the DL750 drivers and I can access them from labview, but I am a bit lost as to getting to communicate with the scopecorder, setting up measurements and so on. I am all new to strain measurements and to labview, is there a link or a tutorial that anyone would recommend I refer to?
Regards, tickle

Hi Tickle
It looks like the driver you are using is supported by a third party. I took a look at the driver you are using and it has a couple of examples included with it. I would recommend taking a look at these examples as they are normally a good starting point for communicating with your device. Has anyone else used this device in LabVIEW?
Best Regards,
Adam G
National Instruments
Applications Engineer

Sudden spike in strain measurement

Hi!
I have a PXI 1062Q Chassis, 8108 controller (Windows OS), one PXI 4472 module(Slot 2) & two PXI 4331 modules(Slot 3 & Slot 5). The test scenario involves measurement from strain gauges mounted on a plate which is subject to some impact. But when I try to acquire strain data in the quarter bridge configuration from all the 16 channels at 100 K sampling rate, I find that there is a sudden spike in the data apart from the one observed due to the impact (Please refer attached pics). This spike is seen at exactly the same instant across all the channels. The following are the settings used for strain channel acquisition.
Acquisition Mode :Continuous Samples
Sampling Rate :100K
Samples to Read :10 K
Maximum Limit :1.5m
Minimum Limit : -1.5m
Strain Configuration :Quarter Bridge I
Voltage Excitation Source :Internal
Excitation Voltage :2.5V
Gage Resistance :120
Gage Factor :2
Note: Offset nulling & Shunt calibration are enabled (100K shunt resistor in R3 location)
The application was built using LabVIEW 2011 and DAQmx driver version 9.3.5
Can somebody please tell me what could be the possible reason behind this phenomenon?
Thanks in advance!
Shweta JP
Attachments:
Data with spike_1.png ‏34 KB
Data with spike_2.png ‏36 KB

Shweta_JP wrote:
Hey Lynn!
It's just a 1 sample spike in the positive & negative direction. Could an electrical transient result in such a small duration spike??
Shweta JP
EMC spikes could be of any length....
A good software spike filter is the median filter, here a filter rank of +-3 should do the job...
Looking at your picktures it seems that they appear in a close relation to your trigger ...
Crystal_ball_mode: You wrote impact test.... is there some sort of solenoid/relay/inductive release involved ? Without snubber they can be a source for such spikes....
Spoiler (Highlight to read)
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
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Strain measurment and write to file with NI9237

Hopefully this lab view VI can help some of the novices like myself to acquire strain using the NI9237 and write to a file. The example VI available from NI "Cont Acq Strain Samples (with calibration)" is fine for sampling data and viewing on a chart, but you need to add your own elements if you want to logg data or write to a file.
Since aquistion is continuous, reading and writing data must be done at discrete intervals rather than continuously, or, you will end up with a very large file that can not be easily handles in excel. Also, data gets acquired in "packets" of several samples for each channel, so even if you put a write function within a case structre, as I have done ,and you don't convert the data you get that whole "packet" every time the comand writes to file. Again, you will end up with a lot more data points than you would like.
Though the top level VI is pretty simple, it took me some time and help from many folks for me to figure out what was going on. I thought I would share.
Thanks to Sandra T, Jarrod B, Kyle B, Marc A, Herbert E and Jesse O. for your help
Next goal is to acquire voltage from a different Daq card, convert to load and graph and write load vs. displacement.
hopefully the attached files are the correct method so the VI fuctions with its sub-VI's. If not let me know.
Regards,
Alfonso
A. Lopez
Attachments:
Cont Acq Strain-Qbridge-I-write to file-NI9237.vi ‏199 KB
Measure Strain.llb ‏238 KB

Alfonso,
I'm glad you got your application running. It is also nice that you are wanting to share your code. NI is currently testing a new system that allows community members to share code. If you like, you can also submit your code here.
Regards,
Jesse O.
Applications Engineering
National Instruments
Jesse O. | National Instruments R&D

Errors in strain measurement system

I am trying to measure strain using SCC SG04, SC2345, and M series PCI 6221. The system is saying that it is not installed properly even though MAX is recognizing the devices. If anyone has set up a similar system could they please help out. Project deadline is getting very close and i am in a bad way

Dr. Imad wrote:
what is not installed properly ? the M card or the SC2345 ?
Once the card is installed, go to max and verify that you see it in Max. Once this is done
under
devices and intefaces
right click---create new
select DaqMx SCC-connector block-----SC2345
Then you configure the SC2345, Type, where SG04 is installed (J1....) etc
then you should be able to access it from LabView. You may want to use Daq assisitant first.
Dr. Imad wrote:
what is not installed properly ? the M card or the SC2345 ?
Once the card is installed, go to max and verify that you see it in Max. Once this is done
under
devices and intefaces
right click---create new
select DaqMx SCC-connector block-----SC2345
Then you configure the SC2345, Type, where SG04 is installed (J1....) etc
then you should be able to access it from LabView. You may want to use Daq assisitant first.
I have done as you recommended. The Daq board does show up in max. I have added the connector block and the strain module. That seems ok until i do a self test and it fails. It says in the error message that the device may not be working properly or is not properly installed. I have removed the whole system and reinstalled it only to get the same error message. In the device manager in windows 2000 it says that the DAQ card is working properly. When i go to the drivers tab it says that the driver provider is National Instruments but the date and version are unknown. It is not digitally signed. I have tried to install a driver for this namely NIDAQ7.3CD1.zip and NIDAQ7.3CD2.zip but this doesn't make any difference. The DAQ assistant didn't get it working either.

1520 Strain Measurement

Hello All,
I am using SCXI 1520, Terminal Block 1314 and DAQ 6035 E Card, for
Strain Gauge Measurement.
We have got a Strain Gauge of 120 Ohm with the NI Hardware which was
connected to CH02(One of the 8 channels provided), Now my problem is
that if I connect the Strain Gauge to some other channel(except Channel
2) I am not able to get any readings , and if I reconnect it back to
Channel 2 it gives prorper results.
I have connected the strain Gauge in
a Quarter bridge Configuration(obviously for a Single Strain Gauge) as
per the circuit diagram provided correctly.
I have Pentium -4 , 256MB RAM, Win XP SP2 machine.
Could anybody please try to explain where I am going wrong.
With Regards
Sandeep

I agree, please check this measurement in MAX by setting up a DAQmx Strain Gauge Task, or by using the test panels associated with the chassis if you are using Traditional DAQ. What happens when you change the channel you are using and test it using MAX? Is the signal responsive, but inaccurate? Is it just displaying 0, 10, -10?
If you are able to measure correctly, then just make sure you are changing the channel in your program.
If the signal is there and responsive with what is happening to the strain gauge, but inaccurate, you may have an offset error that can be corrected with the calibration resistor. The completion resistors of the 1520 should be checked as well. Make sure they are the correct values.
http://digital.ni.com/manuals.nsf/websearch/56E77CCD7B41AA8386256968005BBB73
The DAQ Driver version would also be helpful if you are still having problems.

Angle and Strain Measurement

Hey Guys,
I'm a LabView newbie and want to program a LabView-VI which should write the measurement of a Heidenhaim angle measurement device and multiple strain gauge strips in one data file like this:
angle | strain1 | strain2 | strain3 ...
The strian gauge strips are connected to the Laptop with NI9237 modules and a NI chassis via USB. The Heidenhaim system is also connected via USB.
Can LabView identify the angle measurement system or do I need additional drivers?
I found this post (http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/Heidenhain-ND-287-connect-with-VISA/td-p/2372... and tried to figure out the given example "Advanced Serial Write and Read.vi". But I would be happy if anybody has more information, examples, codes, etc.
Thanks for your help

Hi,
here is an example to measure the angle with a Heidenhaim device :
http://forums.ni.com/t5/LabVIEW/Angle-Measurement-Using-Absolute-Encoder-and-LabVIEW-FPGA/td-p/14114...
Aurelie

Dynamic strain measurement

Sir,
My experiment involves the measurement of strain on the specimen on the application of torque.
I'm using SC-2043SG for the quarter bridge ,with an internal excitation of 4.13V.
The problem is that when i apply 1.5 Nm and 2Nm torque, both are showing the same strain, 243 microstrain.
Whereas in the digital multimeter they show .7mV and .9mV respectively.
The strain is supposed to vary , which is not happening for every 0.5Nm. The multimeter is showing a
variation of .1mV for every 0.5Nm increase in torque. But this is not being shown in the strain output. Only
when it reaches 3Nm it shows 486 Nm. But this remains the same even for 4Nm.
external signal conditioning is also not helping.

thanks for replying ,
The DAQ device i m using is PCI -MIO-16E4
The DAQmx Device driver version is 7.5 0f 1
im attaching the program i made for my application.kindly see through it
thanks a lot
Attachments:
indu new.vi ‏131 KB

Strain measurement with nı 9235

hello everyone
I am user of NI 9235 and my question is about measurement of strain gages. I attached the gages to material propertly and connect to nı9235 with embeded gage factor and ets. then I calibrate just with using button of calibration as attached pictures. I am not sure am I measure right data. I checked NI website, there is something mention about shunt calibration but it doesnt offered at NI9235.
Could anyone give some information about my problem?
Attachments:
IMG_20150323_121018.jpg ‏5751 KB
IMG_20150323_121005.jpg ‏5594 KB

Hi,
Here is a National Instruments white paper http://www.ni.com/tutorial/7130/en/ that walks you through taking a strain gauge measurement. This should assist you in setting up your measurememnt. What about the data makes you think it is not measuring correctly?
I have found some other resources that may prove helpful http://www.ni.com/white-paper/11488/en/
http://forums.ni.com/t5/Signal-Conditioning/shunt-calibration-NI-9235/m-p/2460276
Please let me know if these are helpful or if you are still having problems after this. Also it appears you are trying to use a DAQ Assisitant and from what I have read you cannot due a shunt calibration using DAQ assistant.
Matt P.
Applications Engineer
National Instruments

Can I measure dynamic strain with a SCXI-1531 and how steady is the excitation current?

I am looking at the possibility of using an SCXI-1531 module to take measurements from a single strain gauge. I am only interested in the dynamic content of the signal and so am considering using the constant current excitation method which does not require bridge completion. Is there anyone out there that has tried this or could advise me as to whether this module is suitable?
Having read the spec of the module, it looks promising except for the data on the excitation current which states:
"Accelerometer input excitation current: 4mA +/-10%, 24V compliant."
Now, does that mean that the current will be steady at a value in the range 3.6 - 4.4mA or that it may fluctuate within this range during measurement? The latter would not be acceptable for my application as this would be indistinguishable from a variation in strain.
Thanks for any help.
CAS

Hi CAS,
Essentially the excitation provided by the module will not allow you to acquire as you would like.
However, the good news is that you are able to disable the excitation provided by the module, and provide your own external excitation. You should then be able to acquire the signal using the SCXI-1531.
To disable the excitation in LabVIEW using DAQm, place down a DAQmx Create Channel.vi and then configure it for Strain measurements. Then you can create a control/constantto wire to the Bridge Information Terminal by right-clicking on the terminal and selecting control/constant. Within this cluster control/constant will be an enum element where you can specify the voltage excitation source to be external.
I have attached an example VI demonstrating this.
Hope this helps.
Steve
Attachments:
Excitation Example.vi ‏18 KB

I can not measure strain gauge

I'm trying to work for strain gauge measurement with scc-sg04, sc2345 signal conditioner and ni-6223 DAQ card. Internal +2.5V supply I have used as excitation voltage. I want to get the data via Measurement & Automation explorer and I have created a task for strain measurement. I have selected the SCC1Mod1/ai0 channel for this purpose and adjusted task timing to Continuous mode. When I have pushed the Test button, Analog Input Test Panel is shown and observed strain value is -0.0021. This value do not changes while I pushing my finger to the load cell.
With +2.5V excitation voltage can I see the any changes for output (note that manufacturer recommends 10V excitation voltage).
Message Edited by immortal on 11-12-2007 02:11 AM
Message Edited by immortal on 11-12-2007 02:12 AM
Attachments:
fig.JPG ‏89 KB

Dear Hani,
Thank you for your reply firstly.
I connect external power as you give but there is some problems I have encountered. I connect cables of DC voltage supply to input of the load cell (DC supply is not running) but acquired data (there should be only noise ideally in this state) is fluctuating (See q3_1.jpg). After, I run DC supply and there is a sinusoidal wave in this phase (See q3_2.jpg). If I push my finger to load cell, DC value of this sinusoid changes only. So, I have a big problem with my external excitation supply .
The other problem I've encountered is Vex value of external excitation. I change Vex source to external and Vex=10V and my task is not working and gives an error as "requested value is not supported value for this property" (See q3_3.jpg). I couldn't understand why this error occurs.
Waiting your reply...
Attachments:
q3_3.JPG ‏76 KB
q3_1.JPG ‏31 KB
q3_2.JPG ‏30 KB

Issue with fixed point number output from 9219 module for full bridge measurement (cRIO/FPGA)

Hi,
I have a question regarding the fixed point output acquired from a 9219 module (in FPGA on a cRIO) when setup to acquire a strain measurement (full bridge).
Software: Labview 2009
Hardware: cRIO-9012 (NI-RIO 3.2.1), NI-9219 module
The 9219 module is configured in the project as follow:
Ch0: Full-Bridge +/- 7.8mV/V
Ch1: Voltage +/- 4V
Ch2: Voltage +/- 15V
Ch3: Voltage +/- 60V
The calibration mode is 'Calibrated' so the FPGA outputs fixed point numbers.
My issue is that the precision of the fixed point number for Ch0 (strain) is "(fixed point <+/-32,-1>[-2.5e1,2.5e1]:1.16e-10)", which indicates that the fixed point number is a value between +/- 0.25 and not the +7.8mV/V as I expected?
The fixed point number does not change in precision whether the range for the strain measurement is set at +/- 7.8mV/V or +/-64mV/V (the two available options).
As the fixed point number doesn't change precision I'm assuming that changing the range of the strain measurement changes the resolution of the acquired number? And as such I will need to perform additional scaling on the fixed point number to convert it to the expected range?
There is no mention of scaling of the voltage or strain measurements mentioned in any documentation or examples, with the only scaling example provided for the thermocouple measurements.
Any help/clarification is much appreciated.
Regards,
Mike

Hello Mike,
Hopefully I can help clarify some of the behavior you are seeing.
My issue is that the precision of the fixed point number for Ch0 (strain) is "(fixed point <+/-32,-1>[-2.5e1,2.5e1]:1.16e-10)", which indicates that the fixed point number is a value between +/- 0.25 and not the +7.8mV/V as I expected?
For calibrated values on the FPGA VI, the returned data is a Voltage measurement, not a directly calculated strain value. Based on the specified ranges for the 9219 in a Full bridge configuration, 250 mV will encompass all possible input values, at the module provided excitation (2-2.7V dependent on the sensor gage resistance).
The fixed point number does not change in precision whether the range for the strain measurement is set at +/- 7.8mV/V or +/-64mV/V (the two available options).
As you may notice from the fix-point definition, the fixed point data contains 32-bit precision which is larger than the acquired precision of 24-bits provided by the 9219. The fixed point data-type is coded to accept input encompassing both the range and precision of the instrument; such that, no additional coercion of the input data values is required based on user-defined software settings, i.e. the bridge sensitivities +/- 7.8mV/V or +/-64mV/V.
As the fixed point number doesn't change precision I'm assuming that changing the range of the strain measurement changes the resolution of the acquired number? And as such I will need to perform additional scaling on the fixed point number to convert it to the expected range?
The documentation does not clearly define that by varying the discrete levels of strain input (+/- 7.8mV/V or +/-64mV/V) the range of the ADC on the module is also adjusted. I am working to follow up further on this topic, to provide a clarification on the module documentation. As for scaling, the voltage values acquired regardless of the ADC resolution will still be related strain via the bridge sensitivity. The resolution of the ADC will simply define the smallest measurable change in the strain value.
There is no mention of scaling of the voltage or strain measurements mentioned in any documentation or examples, with the only scaling example provided for the thermocouple measurements.
For converting the acquired voltage values to a strain measurement, I would recommend the documentation linked here for a detailed explanation on strain calculation. Often, users will forward the acquired voltage data as fixed point values through a DMA FIFO to the RT controller on the Compact RIO; such that, they may handle conversion from voltage to strain using floating point math in real-time.
I hopes these responses provided a bit of clarity. I will continue to work to provide additional information on the 9219 specification information. Please post back any further questions.
Cheers!
Edit: Forgot to add the link.
Message Edited by Pcorcs on 04-14-2010 04:55 PM
Patrick Corcoran
Application Engineering Specialist | Control
National Instruments

Ni 3214 strain measurements

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