I just Googled USB scale. It looks like there is already such a thing available:
NorthShore Care Supply--Pelouze Digital Rate Computing Scales
NorthShore Care Supply--Pelouze Digital Rate Computing Scales
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I just Googled USB scale. It looks like there is already such a thing available:
NorthShore Care Supply--Pelouze Digital Rate Computing Scales
For the next step, amplification, we need to know:
What are the voltages on E+ S+ and S- relative to E- (ground)?
How much does the voltage between S+ and S- change between nothing on the scale and the heaviest object on the scale? You'll need a voltmeter that can read in the millivolts for this.
From this info we can design an amplifier to boost the signal to a 0-5V range suitable for a PIC's ADC input.
±10% of 1.499kg would mean that the LCD should show between 1.349kg to 1.649kg which it obviously does not.
+Excitation
-Excitation
+Signal
-Signal