Relationship with the millivolt output to the load applied?

[nievz]

Strain Gage

How to know the force (Newton) equals to the millivolt output?

If I have a 30 mV = ????  ===> force (Newton)

Pls help! 

Relationship with the load force (Newton) to the voltage output...................

[Wayne.C]

nievz,

Documentation for your strain gage should specify an output/sensitivity in mV/V.   For example 3mV/V is a common output.  What this means is that with full scale force applied to the strain gage, it will output 3mV for each Volt of excitation.  So 5V of excitation would produce 15mV with full scale force applied.

[nievz]

Wayne.C,

Is there a conversion of for example 15 mV to force (Newton)?

[Wayne.C]

What strain gage are you using?  What is full scale force?  What is output spec'd at?

[Anna_K.]

That sort of information is specific to your strain guage, you will have to contact the manufacturer of the strain guage or take measurements with known amounts of force to find out how the values are mapped.