"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
that. I hope this information helps.
Tutorial

Similar Messages

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.

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.

DAC voltage capped when operating in torque mode with load cell feedback

Hi, i'm doing a tension control on a cable driven system using servo motor. I had connected a load cell as analogue feedback for cable tension into the labview programme suggested in http://www.ni.com/pdf/manuals/371242c.pdf (Figure 13-3. Torque Control Using Analog Feedback Using LabVIEW)
Problem 1: The response between desired tension and actual tension is good until about 80N, when the motor stops responding to higher torque changes. The voltage output in DAC is only 4-5V (max voltage output is suppose to be 10V) and the motor and amplifier had been verified to run up to 200N. What is limiting my DAC?
Settings:
Card: PCI-7350
Analogue input: 0-5V
Problem 2: I had implemented a low pass filter of 30Hz in MAX for the load cells. The effect is quite good for the low tension. However, as the tension increases, the noise increases proportionally too, causing vibrations and switching sounds to be heard at higher tension. Is there anyway to overcome this?
Please help. Thanks

I can't see anything special with your settings, so I currently don't have a clear understanding, why the output voltage is limited.
Could you please test the analog output? You could do this configuring the axis as an open loop stepper axis. This will allow you to set the analog output with Load DAC.
Does this allow you to output higher voltages?
Could you please do the test with and without signal connection to the analog output? Maybe the input impedance of your drive is too low and pulls down the board's output voltage.
I hope that helps,
Jochen

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

Why is AIGND on SCB-100 connected to mains earth through PCI6031E?

I have a PCI-6031E DAC card connected to an SCB-100. I am trying to measure non-referenced differential signals, and via the application notes realise that i must use two bias resistors to AIGND from the +ve and -ve terminals of each channel.
However i can't quite understand why the AIGND pin inside the SCB-100 is connected to mains earth through the DAC card. Surely any disturbances on the earth due to the operation/swiitching of other equipment on our site will produce disturbances on the reference of the DAC card, and hence effect the data that i am recording?
Or is this connection not direct, i.e through a resistor for example?
Any guidance would be much appreciated.
Many thanks
Mike

Hi,
the resistors are both tied to the same point, ergo any change in voltage on the earth line will appear on both signal lines (aix+ and aix-).
Since this is a differential input, they will be cancelled out as a common mode voltage.
The purpose of the resistors is to prevent the input voltages to the aix+ and aix- floating off. You're measuring a differential voltage, say 10V, but that could be at 50V on the aix- and 60V on the aix+. That would damage the card, and without the resistors, the signals from a true floating source could continuously float up and down.
You're quite correct in the fact that aignd is also pc or system earth, and you can get mains earth signals on this pin, hence the reason we recommend NRSE or differential as the better two input types.
http://digital.ni.com/public.nsf/websearch/1ffcbe3451abee09862562970059881d
http://digital.ni.com/public.nsf/websearch/D509679FFAE2764386256297005D0C9D
Hope that helps.
Sacha.
// it takes almost no time to rate an answer

Connecting the SCB-100 to a Solid State Relay

Hey everyone,
I am trying to hook up a solid state relay to the SCB-100 which is connected to a PXI 6515 device. I was just wondering where I can purchase the connecting wire that is ideal for this purpose. A quick look online has yielded few helpful results. A link to grainger/zoro tools or others would be appreciated. The specifications are: The wire must be able to withstand 25V voltage, 25A current. It should also be easy to wire it into the SCB-100. Any AWG will do.
Thanks!

Hi tompkins92,
Here is some information about AWG cables and their maximum current:
http://diyaudioprojects.com/Technical/American-Wire-Gauge/
Here is a place you might be able to purchase the appropriate wire:
http://www.mouser.com/Wire-Cable/Hook-up-Wire/_/N-5ggs
You can select the voltage and current specifications you want.
I have one question: did you mean 25 mA current? Neither the SCB-100 nor the PXI 6515 can safely handle 25 amps.
http://www.ni.com/pdf/manuals/371224b.pdf
http://www.ni.com/pdf/manuals/372199c.pdf
Regards,
Kelsey Johnson
Applications Engineer
National Instruments
http://www.ni.com/support
(866) 275-6964

What is the pin out connections of SCB 100

What is the pin out connections of SCB 100

Suresh,
Since the SCB-100 is a terminal block, its pin out is dictated by the DAQ device to which it is cabled. Thus, the pin out is available in the user manual for the appropriate DAQ device. Below, I have included a link to the location where the user manuals are available:
Manuals
Good luck with your application.
Spencer S.

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

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!!!

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

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

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

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

Controlling Linear Actuator via Load Cell

Hello,
I need to control the position of a linear actuator based on the force feedback from a load cell (rated up to 100 ft/lbs) connected to the tip of the linear actuator. What I want to be able to do is to set a force and have the linear actuator (driven by a stepper motor) move until it is within 0.1 ft/lb of the force setpoint. Once within 0.1 ft/lb of the setpoint, I would like to hold and control to the setpoint based on a user configured hold time.
I have the following hardware:
PXI-1033 chassis
PXI-7340 Motion controller card
UMI-7764 Terminal Block
P7000 Drive
Omega Engineering Load Cell model number LC201-100
Omega CCT-80 Load Cell Signal Conditioner
Omega FAR-1 Power Supply
I have the + output of the CCT-80 connected to the Analog Input (AIN1) and the - output connected to the Analog Input Ground (AIGND). This output signal is -10V to +10V (verified by DMM)
I have the ADC range set to -10 to +10
I'm reading the ADC as fast as possible (get about 700 samples/second) and this just isn't fast enough to control to the precision that I need. Also, it seems like there is a substantial amount of noise on this line.
Does anyone have any recommendations on improving the speed of the ADC read, or how to reduce the noise on the line?
If my requirement of holding to 0.1ft/lb is too strict for this hardware (7340 motion card) is there something else that I should try?
If I'm missing any other info that is needed to help me out, let me know and I'll update this post.
Thanks!

Hello AMac,
I have a setup similar to yours with a load cell attached to a linear stage. I want to use position control of the stage to apply a set load on the load cell (position-based explicit force control). Do you have a example VI I could look at if yours was successful?
Thanks,
Kyle

"connecting a load cell to scb-100"

Similar Messages

Maybe you are looking for