K: How can I convert voltage to Pounds?

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  • Thread starter Thread starter shankaryr
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    Calculation Voltage
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Discussion Overview

The discussion revolves around converting voltage readings from a force sensing resistor (FSR) into force measurements expressed in pounds. Participants explore methods for establishing a relationship between voltage and force, including calibration techniques and potential software solutions.

Discussion Character

  • Technical explanation
  • Experimental/applied
  • Debate/contested

Main Points Raised

  • One participant seeks a formula or software to convert voltage to pounds, indicating urgency.
  • Another participant questions the nature of the force being measured.
  • Some suggest that the setup may involve a load cell and recommend measuring voltage with known weights to establish a relationship.
  • A participant explains that voltage represents potential and must be related to current to calculate power, raising questions about how to connect current to force.
  • One participant describes their setup involving a data acquisition device and emphasizes the need for a relationship between voltage and pounds.
  • Another suggests applying known forces to calibrate the system and measure voltage changes accordingly.
  • Some participants note that there is no general formula available and stress the importance of calibration through experimentation.
  • A later reply suggests using a strain gauge as an alternative to the current setup.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of calibration and experimentation to establish the voltage-force relationship, but there is no consensus on a specific formula or method to achieve this.

Contextual Notes

Participants mention the need for linearity in the device's response and suggest measuring at various force levels to ensure accurate calibration. There are also references to the limitations of the current setup and the potential need for additional equipment.

Who May Find This Useful

This discussion may be useful for individuals working with force sensing resistors, load cells, or similar devices in experimental or applied physics contexts, particularly those interested in data acquisition and calibration techniques.

shankaryr
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Hi there,

I have converted a resistance value to a voltage level. My objective is to convert the voltage level to force in terms of Pounds. Could anyone suggest me a formula which could be used or a software which can do this. Can I use excel to convert this if there is an already stated formula.

This is kind of urgent and all help is appreciated

Thanks
 
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Is this some sort of load cell ( a weighing machine ?)
The easiest way if you don't have the specs is to measure the voltage with no weight.
Then add 1lb and measure the voltage, then measure it with 2lbs ( or whatever range of weights is reasonable)
 
Voltage is a potential. You need to multiply by the current in order to caculate power, the rate at which work is done.

Force times speed also equals power, so

Voltage times current = power = force times speed, but how would you relate current and speed?
 
I am connecting a force sensing resistor to a data aquisiton device (labjack). The FSR takes in force applied on it and outputs resistance value. Now, i have used a Data acquisition device labjack to convert the resistance value to voltage for which i have used a voltage divider. Now, my objective is to convert the voltage applied to pounds to calculate the force applied on the FSR. For this i need a relationship between force in lbs abd voltage.
 
Ideally, what I would do is to apply a known amount of force (weights in lbs) on the FSR and get the resistance value. But since I am thinking of making this a computer generated output, I need the value to be generated by an electonic device. If i have the relationship I might be able to use excel or probably labview to convert the voltage to pounds.

So, if anyone has an idea, please let me know and it would be well appreciated.
 
Assuming the device is linear then you just need the scale and offset as I described.
Measure the voltage with no load and then measure the change in voltage per lb.

If you need an analogue output from this sensor (eg. 1V = 1lb ) you can do this with a single op-amp.
 
shankaryr, there is no basic general formula that we can give you. You must calibrate your apparatus by applying a known force and measuring the resistance or voltage yourself.

As mgb_phys said, you should do the measurement when there is no force. Also do it with close to the maximum force you expect to use.

If you want to double-check the linearity, you could also do the measurement with about half the maximum force.

Good luck :smile:
 
Thanks. I shall do the above said steps.
 
  • #10
shankaryr said:
Hi there,

I have converted a resistance value to a voltage level. My objective is to convert the voltage level to force in terms of Pounds. Could anyone suggest me a formula which could be used or a software which can do this. Can I use excel to convert this if there is an already stated formula.

This is kind of urgent and all help is appreciated

Thanks

Just use a strain gauge instead.

EDIT: Here is a link - http://www.rdpe.com/ex/hiw-sglc.htm

CS
 

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