Program labveiw to read torque

[mr tyco]

HI, we are trying to set up a data system to measure pressure,torque and position from a potenimeter.Also set up a timing output circuit to contacts on the feild point module which will control a solnoid. We have the pressure vi reading ok, but are having trouble with the others.

We have 3 modules, FP-sg-140 for pressure,FP-ai-110 for potenimeter,and FP-ao-210 for switching timer.Can you help us please.

                                                                                                                                                              Best regards Bruce Mitchell

[RavensFan]

What kind of sensors are you using to measure torque?  Are they strain gages on a shaft? Or something else?

What is the sensor for measuring position?

[mr tyco]

We are using a Futek Flange to Flange reaction torque sensor. (output: CW: 1.6125 mV/V @ 5000 in-lbs).WE are using a potenimeter on a actuator.

[Pie56694]

Hi Bruce,

We would like to help you with whatever trouble you are having with the system, but we'll require more information to do so.  What kind of trouble are you having?  Are you getting errors with the code or FP system?  Do you have programming questions?  If you do, would you please post the code that you have written so far.  What type of architecture are you trying to implement (producer/consumer, state machine, user event, etc.)?  What FP controller are you using?  How are you connected to the controller?  Answers to these questions should get us started.

[mr tyco]

Hi Steve,

             No error codes or hardware trouble with FP. We do have programming questions; mainly our torque readings. We are getting numbers from the FP module but are having trouble going about how to convert to in-lbs. The FP controller we are using is FP- 1601 connected to a wireless router (Linksys Wireless-G Router) to a laptop. Is it a problem if we E-Mail the Labview program to National Instruments [webmaster@ni.com]. because TYCO does not want us to publicly post any program.

[Pie56694]

Hi Bruce,

I you subscribe to Standard Service Program (SSP) or Premier Service Program (PSP) you can create a new Service Request at NI.com/ask.  You will then be able to submit code to an applications engineer via email.  A request for support should not be emailed to webmaster@ni.com.  We may not have to see your code to help in this case.  What is the exact model number of the torque sensor?  How is the circuit connected to the FP module?  What is the range of data you are getting back?  What version of LabVIEW and what version of the FieldPoint drivers are you using?

[mr tyco]

Are torque sensor model number is Futek Model: TFF600. The wire code from torque sensor to FP-SG-140 is as follows: Green to Term. 3,

White to Term. 4, Red to Term. 19, Black to Term. 20.The range of data on torque sensor is Aprox. -0.05125 to +0.05325.The version of LabVIEW we are using is 7.1 are the drivers that came with the software package. No updates have been done .

[Pie56694]

Hi Bruce,

Let's look at the FSH00682 for example.  The spec sheet specifies the rated output is 2mV/V nominal.  The excitation is 18V max and the rated output is 5000in-lb.  This means that every volt of excitation gives 2mV at the rated output.  With the 682 for example, if you excite the sensor with 10V, you will read 20mV when the torque is 5000in-lb.  John at Futek told me that the relationship is nearly linear, but the actual calibration curve ships with the sensor.

You wrote that your sensor is outputting 1.6125mV/V, I'm assuming you got this value from your calibration sheet.  If you were using the AI-110 to measure voltage off the 682 directly, you should use the ±60mV input range for the AI-110 channel.  If you measured 0V, the torque at the senor is 0in-lb.  If you excite the sensor with 10V and measure 16.125mV, the torque at the sensor is 5000in-lb.  If you use y = mx + b, where m = delta_y / delta_x and b is the 0-torque calibration point, you find that every 3.225µV = 1in-lb of torque.  16-bits of resolution over ±60mV gives you resolution of 1.83µV, so you can measure torque changes slightly less accurately than 0.5in-lb.  Please let me know if this helps, and if you have additional questions.

[mr tyco]

Hi Steve,  

          Thank you for the info. you have provided so far.I have tried to reproduce the settings you have posted with limited results.I am using the AI-110 to measure voltage with a the range set to -0.065 to 0.065volts but when i try to excite the torque senor with 10vdc using ethir the FP-A0-210 or FP -SG-140 i get the following errors:  FP-AO-210= (channel is soucing the maximum current allowed) FP-SG-140=  (CHANNEL

[mr tyco]

Hi Steve,  

          Thank you for the info. you have provided so far.I have tried to reproduce the settings you have posted with limited results.I am using the AI-110 to measure voltage with a the range set to -0.065 to 0.065volts but when i try to excite the torque senor with 10vdc using ethir the FP-A0-210 or FP -SG-140 i get the following errors:  FP-AO-210= (channel is soucing the maximum current allowed) FP-SG-140=  (channel is in overcurreny protection mode). I have used an external power supply and seem to be getting good numbers back, Now, the numbers i am getting from the AO-110, what do they represent? Volts ? M/Volt ? or are they numbers i have to convert some how in labview. These are the two main problems right now and again thank you for all your help and effort.

Message Edited by mr tyco on 07-02-2008 12:35 PM