Convert strain to force

[RedSeal]

Can anyone tell me how to obtain continuous force values? I will be measuring the compressive force applied to a load cell by an epidural needle. I am having problems converting the voltage from the load cell to force units. Any example codes would be greatly appreciated.

[Mohan Pawar]

"RedSeal" wrote in message
news:50650000000800000011C30000-1077587809000@exchange.ni.com...
> Can anyone tell me how to obtain continuous force values? I will be
> measuring the compressive force applied to a load cell by an epidural
> needle. I am having problems converting the voltage from the load
> cell to force units. Any example codes would be greatly appreciated.

If this is a brand new experiment, you will need calibration. In principle,
applied force must be known and output voltage read must be due to that
known applied force. Moreover, you will need range of known forces for
statistical confidence. How to apply known force? The answer depends on
your experimental set up. Can you simply use precisely known weights (lumped
masses) to ge
nerate force under gravity? Again the answer depends on if the
equipment permits it. You will need to give more details so others can
suggest.

HTH

*******************
Mohan Pawar

[Conseils]

See the other answer and

Labview 6.1
Select HELP | Find Examples | Search

Use the keyword Strain
Select the example
"Continous Strain Measurement"

Now Calibrate as required (suggestions below)

You can simulate the force measurement device if you know the construction of the device used to measure the force. By constructing an equivalent resistor network and adding a "Simulation" resitor. Alternatively you can purchase bridge calibration hardware.

By weight.....
In this instance I suspect some small Lab weights will be required or use Brass Tacks and weigh them on a scale / balance then divide the number of tacks by the weight obtained for the average weight of each tack.

Coins would be a suitable alternative !! And you can recycle them afterwa
rds.... well buy a beer to celebrate 🙂

[RedSeal]

This is a new experiment. We expect forces up to 100 lb. My first thought was to lay a known weight on the load cell and measure the voltage that this weight produces. I guess my question then is how do I scale this voltage using LabView? Thanks.

[Mohan Pawar]

"RedSeal" wrote in message
news:50650000000500000087620100-1077587809000@exchange.ni.com...
> This is a new experiment. We expect forces up to 100 lb.
Make sure that you are referring to a force and not mass. A laboratory
weight with 100 lb written on it exerts under gravity a force of 100 lbwt or
100x32 poundal (if that is what one calls in FPS system). My suggestion is
to refer to the specifications sheet of your load cell to determine how much
force it can take for its maximum voltage output.

> My first
> thought was to lay a known weight on the load cell and measure the
> voltage that this weight produces. I guess my question then is how do
> I scale this voltage using LabView? Thanks.

That is correct. You might want to us
e at the least 3-4 different weights
and measure corresponding 3-4 different output voltages. Plot imposed
weights against outpout voltages and get an equation for your curve. This is
your calibration equation. Use this equation to find any unknown force from
measured corresponding voltage. Make sure that your input force remains
within the range that defines your equation.

HTH

***********
Mohan Pawar

[zairi]

Hi guys.

I'm doing an experiment using strain gauge. In order to measure the pedal forces on a stationary bicycle, I'm putting strain gauge on the pedal. How can I convert the strain value to force? can anyone help me. TQ.. 😃

Regards,

zairi