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[Reply #15 on:]

Sensors typically used to measure these small forces are not strain gages, but rather electromotive force compensation or EMFC.  A force is generated by a coil in a magnetic field that equally compensates for the unknown mass.  A fairly delicate mechanism is used, a parallelogram of sorts with a simple fulcrum to amplify the mechanical leverage.  These are very accurate and are less sensitive to temperature and big problem with strain Gage's.  A larger problem though is drift, or baseline stability and balances that use strain gages have to employ many software tricks to keep the display stable.  Lastly, you are only asking the sensor to resolve "1000" points (5000mg/5mg) which is certainly reasonable.  Small silicon sensors can resolve this type of loads.  Solid state pressure sensors typically employ these miniature sensors.  The challenge then becomes how to mechanically load a force, rather than a gas pressure. 

[Reply #16 on:]

The only sort of scales, which will work on another planet,  are the ones where you have to balance the two arms of the scale by comparing the object to be weight,  with one or more known, calibrated, masses.

But that doesn't work in space.

[Reply #17 on:]

There is always some gravity, and as long as it applies equally to both arms of the scale,  you are set to go.

[Reply #18 on:]

Perhaps the OP should consider the FSR 402 device mentioned in the other thread today.