How can I measure the force in Newtons using my Setup?

[HummusGuy]

hey ya'll,

So im a beginner, like a real beginner. Im trying to measure the amount of force exerted/needed to reach the breaking point of a bone using the following setup:

The force is exerted using a force sensor (the inelta KMM20-2kN force sensor) connected to a displacement sensor that is touching the moving plate upon which the bone is being tested on.

This System is connected to a USB-6000 which intern is obviously connected to Labview on the PC. 

Since im getting a voltage reading from the displacement sensor because I have a USB-6000, I was wondering if there is a way to measure or get a force measurements from this setup. 

im getting a voltage time graph , upon which I can roughly interpret the breaking point position but a force measurement would be ideal. 

I've included a photo of the setup around the force sensor. Im more than happy to provide any more necessary info. 

Any help would be greatly appreciated. 

[Bob_Schor]

Tell me if this is correct -- you have a force sensor and a displacement sensor, you have a USB 6000 connected to the displacement sensor, and you want to know how to measure the force in Newtons, right?  How about wiring something to the force sensor?  

Bob Schor

[ZYOng]

Measuring Load with Bridge-Based Sensors

A load cell requires excitation voltage to work. USB-6000 does not support providing the excitation voltage. You will need a strain input module like NI-9237. Once you have the correct module and wiring, you can configure the DAQmx task to convert from voltage to force.

Use NI DAQ Devices for Load, Pressure, and Torque Measurements

Unless you use another signal conditioner which provides the excitation voltage like those in page 4 of 170031_inelta-datenblatt-kraftsensor-KMM20.pdf

[HummusGuy]

Hi, 

well the problem is that the force sensor is useless since i cant obtain any info from it, so my issue more correctly would be how do I obtain a force measurement from the displacement sensor connected to the USB-6000, is there a way to convert the voltage obtained into a force measurement? 

[HummusGuy]

Hi, 

unfortunately I don't have access to a signal conditioner listed in page 4 of the documents you sent. Which I guess means my question will be is there a way I can convert my voltage measurements (obtained from my Displacement sensor connected to the USB-6000) to force in Newtons?

[ZYOng]

---

@HummusGuy wrote:

Hi, 

unfortunately I don't have access to a signal conditioner listed in page 4 of the documents you sent. Which I guess means my question will be is there a way I can convert my voltage measurements (obtained from my Displacement sensor connected to the USB-6000) to force in Newtons?

---

Unfortunately no. The load cell won't be able to work properly and output a working signal without an excitation voltage.

[HummusGuy]

Okay so it turns out I have the Inelta IVM2-DMS in my system. Sorry I failed to see that and mention it. 

[ZYOng · Accepted solution]

Since you are not using a specialized strain input module but a normal DAQ module, you need to understand how a load cell work. Read Load Cell & Force Transducer - How It Works • ANYLOAD Weigh & Measure if you are not familiar with the working principle of a load cell.

IVM2-DMS provides an excitation voltage of 5V in 4-wire mode, hence at a full scale of 20 kN, the output voltage is 2 mV.

V_out = V_ext * Characteristics Value = 5 V * 2 mV/V = 2 mV

We can double confirm this using Load Cell Millivolt (mV) Output Calculator

Since USB-6000 does not support using a force task, you can only acquire the signal using a voltage input task, then use NI-DAQmx Custom Scales to convert from voltage to force. We can use a map ranges scale which maps [0-0.002] V to [0-20000] N. Besides, IVM2-DMS amplifies the mV signal from the load cell to the output range of +/- 12 VDC. You should use the amplification from this signal conditioner since USB-6000 has an input range of +/- 10V. Once you have figured out the gain value configured on the pin 6 and 7 of the signal conditioner, you can use the amplified value in your pre-scaled value of the map range scale.