Configuring Load Cell [ NEW ] Feild Point

Hi, I'm trying to set up some Data acquisition from a load cell through my FeildPoint AI-110. The Load Cell I have is rated to 500KG and has a Out put of 2.997 mV/V. I can connect the load cell to field point and display the voltage difference in Max, but I’m struggling to use this to get any kind of scaled reading to using in Labview.
Can any one help.
Many thanks

I think the attached should get you pretty close. The top section uses just the constants you posted and
assumes a constant excitation voltage of 12.25. The bottom section uses the actual, current excitation
voltage when the measurement is made. I think this second approach will probably give you better long
term results.
The bridge voltage is the voltage displayed in MAX.
Matt
Message Edited by Matthew Williams on 07-04-2007 08:48 AM
Attachments:
strain_example.vi ‏34 KB

Similar Messages

Question on Measuring Lift Force for MAV Ornithopter for Student Project using Load Cell

Hey everyone!
I am new to these forums so bare with me, please. I am part of a senior design student group working on making a micro aerial vehicle ornithopter (generates lift by flapping its wings) similar to this Design.
We are using this load cell connected to an AD620 Op-Amp circuit that basically has two input wires from the load cell coming into the op-amp with a gain of 100 (there is an Rg resistor with 500 ohms in the circuit). The load cell and op-amp circuit are both powered correctly with 10 V and +-15 V, respectively. There are two output wires coming out of the circuit. One comes out of the 6th terminal of the op-amp, and one is connected to ground. If we turn on everything and test the output of the circuit with a multimeter there is little if no fluctuation in the output voltage, which is about .25 V with zero load. If we add precise weights and form a linear graph of the output voltage vs. weight, we can find that there is about .0045 volts/gram relationship.
Here comes the part we we are having trouble. It seems as though the circuit it working correctly, but when we try and hook it up to our USB-6221 DAQ Board though the ai0 (or any analog input) and confirm a LabVIEW program to read the output, we get a ton of noise along with a weird looking graph.
Here is a picture of the front panel that shows the output we are getting http://img130.imageshack.us/i/frontpanelg.jpg/
Basically, I would have though we could get a straight line that continuely increases or decreases depending on the load on the load cell. Why would it graph a ton of vertical lines? I would think it would be just one data point per time value?
Here is the simpler block diagram just to test the output: http://img26.imageshack.us/i/blockdiagramsmall.jpg/
Here is the main block diagram that we were going to use to convert to force, etc. but its not working (no need for while loop?): http://img15.imageshack.us/i/blockdiagrambig.jpg/
The properties of the DAQ Assistant VI is as follows:
input range: -10 to 10 v
RSE terminal configuration
acquisition mode: n samples and not sure how many samples we want to read or how fast. we had 1k hz and 100 samples and the image above is basically what we got it the program runs continuously.
I don't know what else I can tell you, except that if anyone helps me you would be like a godsend to our group. It would be very much appreciated
Thanks!!!

As I am unable to look at youor images (the corporate filter here is blocking the url) I can't see what you are describing. I will say that a multimeter will not show fast transitions that will show up in a LabVIEW/DAQ application, so using a meter usually doesn't tell you that much about signal "cleanness". How long are the wires from the op amp/load cell to the DAQ? How long are the wires, and what type (shielded, twisted pairs, untwisted pairs, etc.) from the load cell to the op amp. The output levels of the load cell are usually quite low, so the possibility of also picking up "environmental" electrical noise is very high, and this will be amplified as well. Since the output of the op amp is higher, the noise introduced between it and the input to the DAQ is less of an issue, but there as well. So making sure that signal wires are properly shielded and grounded is important, and there are long papers describing this for low level analog signals. Since the load cells desired output will probably vary relatively slowly (a few Hz) it may also be helpful to put a simple low pass filter before the DAQ.
You should insert the images into your post, as jpg, or png (you have jpg images) Not bmp! (this is for others that might read your post, yours are jpg which should be ok). Generally most of us won't or can't go to links, corporate network filters and corporate policies frown on it, too much maleware lurking at the end of unknown URL's
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion

Modbus communication with a load cell

Hello..!
I'm a new user of LV and I try to communicate with a load cell by RS232 modbus.
After installed NI Modbus Library I created a master VI with labview 8.6 using these library, and I can obtain a communication with load cell , these value are added into 1 register U32Bit, and it's okay, if I press a load cell I can see the values go on.( from 0 to 65535) . Now I want to show on front panel the value in KG , as decimal point,, for a right interpretation of value for my customer, so I added a block array to unbundle than I convert a value with I32Bit ( -32768 to 32768 ) with an indicator, but I can't see any values..
I suppose I doing something of wrong ( conversion ), I read some KB, but I can't see a suitable solution..
Can someone give me a link or information to show me an example to convert this value..?
Thanks in advance for any helps..
Configuration of MAster VI:
Read holding register
Starting address 2012 ( query for obtain net value from the load cell)
quantity 1
Slave address: 1
RTU
9600
Com 3
parity none
Solved!
Go to Solution.

Hello Ravens,
I tried to use your good advices and finally I can communicate correctly with my trasducers showing on front panel the right value ( Kg). Has been a problem of conversion from output of register ( U16Bit as 0-65535 ) to I16bit ( -32765 to 32765).
Thanks very much for your help, and I hope to chat again for new challenge...
Have a nice WE
Julio
Attachments:
Comunicazione Modbus load cell.jpg ‏46 KB

Generate PWM signal with 6602 utilizing load cell feedback

Hi Everyone,
I am new to LabVIEW so I apologize if this question is elementary but I really need some help with the coding. First of all, I need to generate 8 independent PWM signals to control 8 separate linear acuators using the NI 6602 board. I have each actuator wired to their own COUNTER OUT pins and ground on the SCB-68 that is connected to the 6602. The specs for the actuators state that it will take an input of "RC input range of 1.00 to 2.00msec pulse widths @ 55Hz. Bandwidth=.44to160Hz. Period from 6-23 msec". How can I code for these PWM signals given the specs from the manufacturer?
In the end I need to be able to not only control these actuators based upon duty cycle, but based upon the load each actuator is applying. Each actuator has a load cell in series measuring the tensile force through the load cell (the actuators will be pulling on strings). Each load cell is wired to a NI 9237 in a NI 9074 block that is connected via USB to the same computer. So first comes first, how can I code for the load cell output to be brought into the LabVIEW environment?
My last question is pulling this all together. How can I code so that I can input a specified load into LabVIEW and then based upon the value the load cell is reading, the duty cycle of the PWM will be adjusted until the the desired load is achieved?
Thanks in advance for any help! Also, I know that this is quite a complex questions so if you can even point me in the direction of resources that would be helpful, I would greatly appreciate that too!
Thanks,
Ryan

Hello Ryan,
Here's a tutorial on generating PWM with LabVIEW:
http://zone.ni.com/devzone/cda/tut/p/id/2991
How are the load cells outputting the data? Is it an analog signal? If so, you can read that in using an analog input task, and run that in parallel with the PWM task. Then you can modify the frequency and duty cycle inputs that you're giving you the DAQmx write inside the PWM code based on the analog input. By putting the DAQmx read and the DAQmx write in the same for loop, you can read from one and modify the other at the same time.
Here's a tutorial that shows a lot of useful information for using DAQmx within LabVIEW:
http://zone.ni.com/devzone/cda/tut/p/id/2835#toc6
If you're interested in getting better at LabVIEW in general, NI has some learning materials available here:
http://www.ni.com/academic/students/learnlabview/
Let me know if you have any further questions once you've gone through those first two tutorial links.
Colden

Data acquisition from a 250N Load cell

Hi ,
I am very new at using the Labview.I am using Labview 6i(PCI 6052E).The load cell(250N) is connected to a pump.The pump has 2 bags.One of them is filled with water and the other is empty.I want to load the bag which is empty from the bag filled with water using the pump.The load cell is connected to the bag which is filled with water.I am trying to aquire a volatge signal continously from a load cell and display it on a chart.
My program has no errors and I am able to run the progam.But it is not aquiring any signal.Could u please help me out.Attached is my code for the same .
-Manasa

Hi Manasa,
Make sure you are handling your errors in your code. You can do this by wiring your error clusters through your VI and then terminate them in a General Error Handler VI. If you are doing this, make sure that your device works in Measurement & Automation Explorer (MAX). Do this by opening a test panel and verifying that you can get a known voltage (like a battery) to read correctly. If you can successfully get a voltage in MAX, try running one of the example programs. You can find them at Help » Find Examples..., then browse to hardware input and output. If you can get an example program that is similar to what you are trying to do to work, try comparing your code to the example.
Please post back if you have any questions. Have a great weekend!
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District Sales Manager for Boston & Northern New England
National Instruments

Data acquisition from switching 500lbs load cell to 100lbs load cell

I am using 500lbs load cell, and acquiring data by inputing 2volts from 2345 signal conditioning board, and sensor output is connected to SCC-AI03 pin 3 and 4 , and configure this load cell to a channel using NI MAX, data neighborhood, traditional NI-DAQ virtual channel, the physical quantity is voltage set at range -10 to 10, and sensor also set at voltage with no scaling, but, I couldn't get any signal when 100lbs load cell is use, the difference of this 100 lbs load cell is the rated output is at 2.958mV/V, while the 500lbs rated at 1.8295mV/V , how should I do this?
Thanks.

Hi,
At this point, it is difficult to determine exactly what is happening to your acquisition. Could you please provide some additional information by answering the following questions:
What voltage are you reading with the 500 lb load cell?
Would it be possible to connect your load cells to a DMM and see what voltage reading you receive? If so, what do you see?
What is specifically happening when you connect the 100 lb load cell?
I also noticed that you are using the Traditional NI-DAQ (Legacy) driver. I recommend upgrading to the NI-DAQmx driver. Here are a couple of links with more information about DAQmx:
Advantages of NI-DAQmx:
Transition from Traditional NI-DAQ to NI-DAQmx:
Learn 10 Functions in NI-DAQmx and Solve 80% of Data Acquisition Applications:
Regards,
Hal L.

Not getting accurate readings off a calibrated load cell

I'm using a Cooper Instruments 200 lb load cell connected to a SCB-68 connector box hooked up to a 6036e DAQ card, and I'm having trouble calibrating it. (I've done this before, but it's been a while, and something just isn't working right.) So, I'm using the calibration wizard (the channels are set as Custom Voltage with Excitation), hanging a bunch of known weights from the cell, entering the values, and all that is going fine. However, when I go to use the load cells (in a very simple VI that just reads the value from the cell), it's reading consistently low by 2-3 pounds. I'm using a 10 V excitation signal, and I set the low end of the Signal Input Range to 0 (it kept wanting to set -5=-5 in the calibration when the low end was -5V, and that was even worse). I've tried modifying a custom scale, and that isn't fixing the problem either. Has anyone encountered this before or have any ideas on what else we can try?
Thanks,
Eric Martell

Hi Eric,
This is a curious problem. Is it every point that has a constant offset or does the offset vary from point to point?
Also what is the model number and sensitivity of your load cell? Have you gotten it to read correctly before? You mentioned that the values were stable out to the fourth decimal place, but haw significant is this decimal place? For instance, when I open the calibration wizard, the values can jump around depending on what I am measuring. If you load cell has a sensitivity of 1 mV/lb, then this could be large variations depending on what the decimal point was when you saved the value.
With regards to my mentioning averaging, when you first click the calibrate button in the DAQ Assistant, the first screen has a Number of Samples to Average control and a Rate control. If you leave the # of samples to average at 1000, but change the rate to 10,000, do the values begin to vary?
Regards, Mallori M.
Mallori M
National Instruments
Global Customer Education Program Mananger
Calculate the time you will save with NI Training

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We have BW 3.5 and R/3 4.6C
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Michael,
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I down loaded the new iwork update. Now when I create a docume

I hate the new 5.0, and am having the same issue. Because I created or opened and saved several documents in the new 5.0 before I realized how bad it is, I had to figure out how to make them usable again.
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Any enhancement to increase pick time, do not want new shipping point

Have 1 customer that requires a longer picking time, prefer not to create a new shipping point for a one off case.
Would perfer to write an enhancement so the material availability date is 5 days before goods issue date (5 days pick time) instead of our normal 1 day. A new ship point would work great with 5 days pick time but big change for users.
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Setup new access point 1200

hi
i have problem in install new access point 1200
the access point now not connect to any device iam connect the access point using ethernet cable to PC to configure it i try to using GUI but i can not iam setup the PC with ip address 10.0.0.2 and GW 10.0.0.1 and i try to enter to access point but i can not
i try to use CLI and i connect the access point to PC using console cable and now iam enter to it after the access point start i try to enter to config ter but i can not i get error when i check the command i can not see this command and when i read the manual its tell me to setup ip address using command (lwapp ap ip address) and i try to save ip address using command wr mem or copy run start but i cannot i get error
in prevelig mode i get only this command
clear Reset functions8B5E500 00001537 61300D06 092A8648
clock Manage the system clock
crypto Encryption related commands.
debug Debugging functions
dir List files on a
led LED lock Lock the terminal
more Display the contents of a file
name-connection Name an existing network connection
no Disable debugging functions
ping Send echo messages
pwd Display current working directory
release Release a resource
reload Halt and perform a cold restart
rename Rename a file
renew Renew a resource
rmdir Remove existing directory
save Start to save raise_interrupt_level stack
send Send a message to other tty lines
set Set system parameter (not config)
show Show running system information
systat Display information about terminal lines
terminal Set terminal line parameters
test Test subsystems, memory, and interfaces
traceroute Trace route to destination
undebug Disable debugging functions (see also 'debug')
upgrade Upgrade software
verify Verify a file
where List active connections
how i can setup it and how i can enable the radio
when i see sh run i see that the ip address is dhcp
can any one help me please
thanks

Hi Nassem,
It looks like you ended up with a Lightweight AP (LAP Part#) instead of an IOS AP. This can be fixed;
Reverting the Access Point Back to Autonomous Mode
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html#wp161272
You can convert an access point from lightweight mode back to autonomous mode by loading a Cisco IOS Release that supports autonomous mode (Cisco IOS release 12.3(7)JA or earlier). If the access point is associated to a controller, you can use the controller to load the Cisco IOS release. If the access point is not associated to a controller, you can load the Cisco IOS release using TFTP.
Using a TFTP Server to Return to a Previous Release
Follow these steps to revert from LWAPP mode to autonomous mode by loading a Cisco IOS release using a TFTP server:
Step 1 The static IP address of the PC on which your TFTP server software runs should be between 10.0.0.2 and 10.0.0.30.
Step 2 Make sure that the PC contains the access point image file (such as c1200-k9w7-tar.122-15.JA.tar for a 1200 series access point) in the TFTP server folder and that the TFTP server is activated.
Step 3 Rename the access point image file in the TFTP server folder to c1200-k9w7-tar.default for a 1200 series access point, c1130-k9w7-tar.default for an 1130 series access point, and c1240-k9w7-tar.default for a 1240 series access point.
Step 4 Connect the PC to the access point using a Category 5 (CAT5) Ethernet cable.
Step 5 Disconnect power from the access point.
Step 6 Press and hold MODE while you reconnect power to the access point.
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Step 8 Wait until the access point reboots, as indicated by all LEDs turning green followed by the Status LED blinking green.
Step 9 After the access point reboots, reconfigure it using the GUI or the CLI.
From this doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html#wp161272
Hope this helps!
Rob

I can not uninstall bonjour or itunes. I get a error message that it is on a netwok resource that is unavailable. help get it off so i can load a newer version.

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Doublechecking before proceeding:
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Is there any way to force jvm load a new class?

I write a standalone command line program. This program calls a function which I added to an existing class. the existing class has run run for a while by other processes.
When I run my command line program, it can not find the function I added to the existing class. But I am 100% sure I have overwrote the existing class file with my new copy. It looks like the old class file is still in effect.
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What you need to do is to put the class file in question is a directory or jar which isn't on the class path. And make sure that no class file of the same name exists on the classpath (because that will be loaded in preference).
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VI to measure Load Cell

Hello everyone,
So I'm extremely new at this and really need some help. I need to create a VI that is going to be able to read the force using a load cell.
if anyone can help me I am willing to pay for your time, I don't have much time to learn on my own so I need the help of someone.
I have a power supply load cell and DAQ
please email me if your willing to help me and make some money
Power Supply: http://www.testequipmentdepot.com/bk-precision/power-supplies/1786a.htm?gclid=COahppSjtbUCFQuqnQodmF...
Load cell: http://www.omegadyne.com/ppt/prod.html?ref=LC401&flag=1
DAQ: NI USB-6008
[email protected]

Hi,
If you need to acquire voltage from your load cell with a USB-6008, you can run the attached VI.
Regards,
Attachments:
Voltage.vi ‏34 KB

Load cell calibration

Hi there,
New to Labview. Working on a little college assignment and am looking for a little bit of help. I have a micro load cell hooked up to a myDAQ and I'm attempting to calibrate it to get a make-shift weighting scales. I have attached my vi below. So far I have been able to calibrate it to an extent, but the precision is quite poor. It seems to fluctuate +/- 30 grams. I've been told that the error on the load cell is +/- 5g so I would like to get it a little closer to that. Any help would be greatly appreciated.
Load cell
http://www.phidgets.com/products.php?product%20id=3134
Attachments:
Scales new 15_2.vi ‏408 KB

Add a (INAXXX) ampifier with 100 to 400 times amplification ...
The rated output is 1mV/V so you get 5mV at max load and you also need to measure the exitation voltage .. the myDAQ spec tells that it's not exactly 5V ....
If you can't use an external amplifier, use the analog inputs in differential mode and 2V range, and use three 2.2k resistors to divide down (1/3) the supply voltage.
use a low samplerate (twice your line freq) mean as much samples as possible.
Assuming that the supply is only slowly drifting, measure the supply only (50 samples), sensor only (100 samples), and supply again (50 samples)
Mean the supply and the senor output and use the ratio (U_mean_sensor/U_mean_supply) for your calibration
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

Configurin​g Load Cell [ NEW ] Feild Point

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Configuring Load Cell [ NEW ] Feild Point