9237 + full-bridge load cell: load cell_null_off_shuntcal.vi - error 200077

I'm trying to use
load_cell_null_off_shuntcal.vi with load cell (Honeywell Model 31,
unamplified). I am using LabView 8.6, cDAQ-9172 and NI9237. Inputs:
internal excitation10V; mV/V 2.1492 (calib. sheet); max weight 10 lbs; bridge
resistance 350 ohms (Honeywell specs); 9237 internal shunt resistance 100
kohms; shunt location R4 (default setting). Have selected "Do offset
null" and "Do shunt cal".
Error -200077 occurred at DAQmx
Perform Shunt Calibration
(Bridge).vi:1 Possible reason(s):
Measurements: Requested value is not
a supported value for
this property.
Property:
AI.Bridge.ShuntCal.GainAdjust
You Have Requested: -61.980405e3
Valid Values Begin with: 500.0e-3
Valid Values End with: 1.500000
If "Do shunt cal" green
button not selected, no error. Gain adjust should be approx 1. subVI
DAQmx PerformShuntCalibration (bridge).vi contains "Call library function
node" which is locked (?).
Any ideas?
What is the correct shunt element
location for a full bridge load cell? Changing this location does not eliminate
error.
Solved!
Go to Solution.

Hello CFJ,
The problem is most likely in your external connections of the NI 9237 and the load cell. As referenced in the NI 9237 Operating Instructions and Specifications, page 9, the SC+ and SC- pins should be connected across the resistor specified in the DAQmx Perform Shunt Calibration (Bridge).vi (in the case of a full bridge it would be R3).
Let me know if you are still having issues with your calibration.
Message Edited by Dan_K on 01-22-2009 04:31 PM
Regards,
Dan King

Similar Messages

9237 with full-bridge load cell: load cell_null_off_shuntcal.vi throws error 200077

Hi,
I'm trying to use the example
load_cell_null_off_shuntcal.vi with a full-bridge load cell (Honeywell
Model 31, unamplified). I am using LabView 8.6, cDAQ-9172 and NI9237. The
load cell is connected to pins 2,3,6 and 7.
The inputs for the VI front panel
are: internal excitation10V; mV/V 2.1492 (calibration sheet); max weight 10
lbs; bridge resistance 350 ohms (Honeywell specs); 9237 internal shunt
resistance 100 kohms; shunt location R4 (default setting). I have selected
"Do offset null" and "Do shunt cal".
This is the error I receive:
Error -200077 occurred at DAQmx
Perform Shunt Calibration (Bridge).vi:1 Possible reason(s):
Measurements: Requested value is not
a supported value for this property.
Property:
AI.Bridge.ShuntCal.GainAdjust
You Have Requested: -61.980405e3
Valid Values Begin with: 500.0e-3
Valid Values End with: 1.500000
If the "Do shunt cal"
green button is not selected, there is no error. I understand that the Gain
adjust value should be approx 1, whereas the one I get is much larger. The subVI DAQmx PerformShuntCalibration
(bridge).vi contains a "Call library function node" which I don't
know how to interrogate.
Has anyone else had experience
with this error? Do you have any advice on:
1)
How to "see" the calculations being
perfomed inside the "call library function node"?
2)
What the correct shunt element
location for a full bridge load cell is? (although changing this location does
not eliminate the error, I can't find this info).
3)
Anything I may be doing wrong with
my inputs to cause this error?
Thanks,
Claire.
Solved!
Go to Solution.

Hi Claire,
You have to physically connect the SC terminals to one arm of the bridge (normally R3). The terminal is not provided for connecting external resistors.
See example
C:\Program Files\National Instruments\LabVIEW 8.6\examples\DAQmx\Analog In\Measure Strain.llb\Cont Acq Strain Samples (with Calibration) - NI 9237.vi
"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!

A/C three Phase motor control using 1/4 bridge Load Cell output and a USB 9172 Daq

NI Assistant,
I am tasked with setting up a Motion Control using two each OMEGA LC712-100K, -50K and -10K load cells to monitor the cable tension on six A/C motor driven winches. I also need to Monitor and calculate a Moment as well as the load slope for Load verses Time.
I have zero time to develop and I have searched your databases for existing Motor Controls to modify.
Should I use Case Structures and then place them in a while loop?
I setup a drawing in Word to visually define the task.
Signed,
Patrick Murphy
Attachments:
Layout for Testing Spars.docx ‏15 KB

Hi Patrick,
The reason why the Motion Control examples will not work for you is beacuse they are meant to be used with the NI Motion boards. Since you are using DAQ boards, the examples are probably not going to be able to help you too much. However, there is one example on the community that might be a place for you to start.
pmurphy wrote: Should I use Case Structures and then place them in a while loop?
What exactly do you mean by this? What do you want in the case structure or while loop?

Force Mapping from Modified Load Cell

I am having some trouble finishing a program that we have been asked to write. Basically, the program is connected to a piece of hardware we fabricated. The hardware (attached below) is basically a wheel with four spokes. Each spoke has a strain gage attached to it on either side. These are connected as two full-bridge circuits. I have been able to get the force output for each of the full-bridges as the maximum value. We have now been asked to create a map of the forces to show where the most force is being placed (assuming uneven distribution). My vision is that it would use colors to show where the forces are, similar to a temperature map. What would I use to go about doing this?
Attachments:
Force Measurement v1.vi ‏106 KB
Modified Load Cell.png ‏267 KB

Look at the Intensity Graph. That will plot data as a range of colors. You will need to do some math to determine the value distributions from your set of strain gauge readings. You may also need to do some geometry/masking to set the force to zero where there is no material.
Lynn

SCXI-1520 AND 700 OHM LOAD CELL?

Will the SCXI-1520 work with a 700 ohm full bridge load cell? I'm a load cell mfg proposing a 700 ohm load cell solution to a customer. He says he doesn't think the 700 ohm cell will work with his 1520. The load cell will can take a maximum 20 VDC excitation and outputs 2 mV/V.

Hi,
Can you verify that the voltage coming out of the thermocouple is correct? You can do this by measuring across the thermocouple using a hand held multimeter. You may also want to input a known voltage into the module (a simple battery would suffice) and see if this produces the correct voltage in Measurement and Automation Explorer.
Abhinav T.
Abhinav T.
Applications Engineering
National Instruments India
LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx
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PASCO Load Cell and NI DAQ Interfacing

Hi everyone,
I have a PASCO Load Cell PS-2200 and I am trying to interface it with an NI-9201 AI (in conjunction with a NI-cDAQ 9172). Instead of attaching wires to the cell's pinout, I stripped a PS2 connector and rearranged the wires to match the pinout of the sensor (which are the strain gauge input, strain gauge output, the excitation voltage of 4.2 and the ground). I connected the strain gauge signal to a channel of the NI 9201 and I am using an external power source to provide voltage to the cell. My VI is trivial and consists of an input DAQ and Lowpass filter.
The problem is that the input signal is obviously not right, it looks periodic for one. The filtered signal appears stable at first but slowly increases over time. And the signal does not respond to applied stresses.
I would really appreciate any help on this. I am a ME sophomore and have little experience with LabVIEW.
Thank you.

Thank you Jignesh and Dave,
Jignesh, I do not have a scope I can measure the ouput with. And no, the cell does not respond to variable loads. Also, please find attached the snapshots you had asked for. The front panel snapshot shows the cell's reponse when under no load
Dave, the module I am using has a 16 bit resolution and within a +/- 10 full inut range, don't we have enough resolution to acquire the smallest change?
Also, from the pinout of the load sensor, the pin for the excitation terminal and the positive strain gaugw output are adjacent. They are not the same terminal. We took every possible precaution to make sure that the terminals of the PS2 connector did not touch during soldering.
Thank you for your help again.
Attachments:
block diagram.jpg ‏159 KB
front panel.jpg ‏390 KB

Closed loop velocity control based on load cell force

Hello,
My application is for a drill, that drills into rocks of various densities for the purpose of collecting rock core samples.
My setup has 2 motors which get controlled, one spins the drill bit at a constant velocity, the other moves the drill mechanism along a Z axis.
For efficient cutting, it is desired to apply a constant force between the drill bit and the rock. I have a load cell which measures the force being exerted by the drill bit on the rock surface, and this force can be adjusted by changing the velocity of the Z axis. So I would like to employ closed loop control to adjust the Z axis velocity to maintain a constant force on the rock.
Platform: cRIO 9073, with NI 9505 & 9215 Modules, Labview 2010 Full with RT and FPGA modules.
The load cell is by Transducer Techniques, and I use their TMO-1 module to condition the signal, the output of which is attached to an input of the 9215 module, where 0-100 lbs equates to 0-8VDC.
The motors and encoders for the Drill and Z axis are connected directly to the 9505 modules.
Right now I am using a modified version the example found in ...\examples\CompactRIO\Module Specific\NI 9505\Velocity Control (closed loop)\Velocity Control (closed loop) - NI 9505.lvproj to accomplish velocity control of the motors.
My questions are:
1) Do I have the appropriate NI hardware/software for this task?
2) With my current hardware setup, what would be an appropriate way to control my Z axis velocity rate based on Analog feedback from the load cell?
3) Development time is a critical factor, so are there any toolkits etc that are easy to get started with that would drastically decrease my development time, or do I already have everything I need?
Thank you for your time
-MK Hokie

1. Your hardware and software look appropriate assuming the motors are compatible with the 9505s. You didn't mention the NI SoftMotion module in your software list which is something you will need.
2. There are a few ways of doing this. One method would be to have a force PID loop that would attempt to maintain a force setpoint by directly outputting values to your torque loop. In this case, the drill would essentially move as fast as it could while maintaining the force setpoint. Another option is to have the force loop output a velocity setpoint. You would then have a velocity PID loop that outputs torque values to the torque loop. By adding this additional velocity loop you could have control over your maximum and minimum velocities. There are likely other alternatives as well, but these are the first two that come to mind.
3. Unfortunately there are no shipping examples that close the loop on force feedback. My advice would be to start with the NI 9505 shipping example and adapt it to your needs. There are quite a few things you will want to change though. Do you know if you will need to use the trajectory generator to move the drill into position before starting the force control?
Assuming you don't need any trajectory generation, you can scrap the entire RT portion of the NI 9505 example and just create the necessary FPGA code. On the FPGA, you won't need the Spline or Synchronization code either because this information would no longer be coming from RT. You could take these out and replace the position loop with a force loop and possibly a velocity loop and your FPGA program would basically be finished. In fact the only real motion IP that you will need is for the encoders (assuming you want velocity control) and PID. Then you would need to create an RT VI that allows you to send down enable, disable, PID gains, and setpoints.
If you do need trajectory generation, you would want to keep most of the example code the way that it is, but then program in a 'Force Mode' that utilizes the force and velocity controly as described above. You could think of it as having two different routines programmed side by side.
Regards,
Burt S

Connection for load cell to NI9237

Hi,
I have this omega load cell part LCKD-10 which is a half bridge load cell that I need to connect to the NI9237. Please advice on the connection.
Thanks
Joelle

Thanks. I need to write out a program which checks the centrality of force. I will be using 5nos of the omega load cell, 1 in the centre(Isolated) and the other 4 at all 4 corners. I'm suppose to firstly calibrate the load cell and then take measurement of the force applied to the 5 load cell and display the result in a form of a radar graph (Just a dot in the centre of the graph to show the centrality of the force). Appreciate if you can provide some procedures or program that I can use or try out.

6-Chan Load Cell Conditioning- Which NI Products?

We are building a machine with 6 strain gage based load cells. We need simple signal conditioning, including power supply, between the 6 load cells and our data acquisition system. What are the NI products we need to buy?

Sure. For simple signal conditioning, go to www.omega.com (Omega Engineering)and take a look at the following Bridge Conditioning Modules:
DMD-460 Series
BCM-1 Series
OM2 Series
All of these devices provide some/all of the capability you require. Omega Engineering has an extensive line of products to support accurate, economical, and easy pressure, force, and strain measurement. (No I do not work for Omega Engineering; however, I have used their products over the last 20 years and have always been satisfied with the results). Omega will also send a complete reference set of their current catalog in "paper form"(about 70 lbs) upon request. These catalogs have technical instructions and application notes that rival those found at NI

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
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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

Load cell simulation with PXI system

Just curious if any of you have tried to do this...
I'm using LabView and my PXI chassis to test a board that interfaces with a load cell. The load cell is 2mV/V with a 3volt excitation voltage so full scale would be 6mV. I was hoping to do a sweep in increments of 1mV. So two signals S1 and S2, e.g. S1=2.000 S2=2.001, S1=2.000 S2=2.002, then S2=2.003 etc...
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I was thinking maybe I could buy some sort of accurate multiplying DAC and control it with the Digital lines from my PXI system. Anyway I was just curious if any of you guys and gals had done something similar...or maybe there is a low cost pxi card that I could use...but
I doubt it...my budget is limited right now.
Thanks and regards

Mashman,
Have you considered using an external reference to increase the resolution of the analog output channels on your 6040E? You could definitely get your code width below the 1 mV level that your application requires. Below are links to a couple of documents that discuss the use of external references:
Resolution of Analog Outputs
Outputting a Voltage Using an External Voltage Reference
Good luck with your application.
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Solenoid and a load cell

Hello,
I have an application where I am using a load cell to measure the weight of a fluid in a container. I found some code that works very well for measuring the weight. http://zone.ni.com/devzone/cda/epd/p/id/5902
My application also involves using a solenoid that opens a valve when a button is pressed and fluid flows out of the container. I need the solenoid to close when a certain amount of weight has left the container. I am not sure how to do this. I am using the compact daq chassis 9172 and a 9237 module and a 9474 module.
Thanks

Howdy lyon,
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I am recording readings from an Omega Load Cell using DAQmx (Continuous bridge example) . A pre-tension force of 5 KN is applied on the load cell. Is there any way of forcing the applied pre-load force to drop to zero so the readings to start from zero?
Thanks!

The way you worded your question in somewhat ambiguous.
You really do not want to remove the physical preload force, do you?
I think what you want to do is to change the readings to account for the preload. That can be done fairly easily if you have complete control over the applied loads and know when there is no additonal load on the cell. In the weighing (scale and balance measurements of force or mass) this process is called taring. The tare is the weight or force without the external load. At the grocery store they adjust for the weight of the container before they add your food.
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If the maximum load is close to the load cell limit, the termperature of the load cell varies, or there are impact loads involved, then this simple taring approach may not be good enough. That is not because of any inherent problem with the method, but due to the things that can cause a load cell to drift or change baseline outputs.
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Adding Phidgets force sensor ( load cell ) to a Labview VI...

I have an exiting Labview VI, program has been running for a few years, now I need to add the Phidgets sensor ( load cell ).
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There are several examples and help info:
1) "Bridge - Continuous Input.VI" from labview help>find examples
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3) http://www.ni.com/white-paper/7138/en
4) depending on what hardware you are using.. https://decibel.ni.com/content/docs/DOC-2018
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"connecting a load cell to scb-100"

I have an scb-100 and want to know if it is possible to connect a load cell to it and if so, how.

It is probably possible, but you have to have some additional circuitry in order to use the load cell. Typically, load cells are comprised of strain gauges which require some kind of Wheatstone bridge completion. Additionally, most strain gauges need excitation. If you can provide the bridge completion and excitation, then you could simply read the output of the strain gauge by connecting the output + and - to your SCB-100. However, setting up this external circuitry can be a little complicated. So, the recommended setup is to use some signal conditioning. National Instruments provides a couple of options regarding signal conditioning for load cells. Below is a link to a tutorial that discusses how to measure a load cell and what hardware is recommended for
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Tutorial

9237 + full-bridge load cell: load cell_null_off_shuntcal.vi - error 200077

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