If an object can be made lighter by introduction of an purely electrical stimulus, does this signify that a thrust has been created within this object, or is there some other mechanism that can explain weight changes in a gravitational field, but not cause thrust in free space, if one were to rule out measurement errors?

There are several aspects of your question I don't understand.

1) How can something become lighter by means of electricity? Weight doesn't change by thrust or electromagnetism. Acceleration does.

2) You say "stimulus" as in "stimulus/response". Cybernetics? What is that stimulus? Do you mean push, transfer of momentum?

3) Thrust within. Thrust for a rocket is nothing to do with "within". The exhaust goes away.

Maybe someone can understand better...

Electromagnetic forces "within" an object can introduce internal stresses but this doesn't make it lighter. 

Electromagnetic forces "on" an object can make it effectively lighter. (this could be considered to be thrust)

What definition of "free space" are you using? If isolated the object would have nothing to push against (though simply radiating photons would give thrust). If just not in a gravitational field the same lightening electromagnetic forces would amount to thrust. 

Edited June 28, 20205 yr by J.C.MacSwell

There are ion thrusters that only work in atmosphere, and would not work in a vacuum. It’s called the Biefeld-Brown effect. https://en.wikipedia.org/wiki/Biefeld–Brown_effect

@ macswell, the free space I refer to is outer space, in microgravity. I am attempting to make a Woodward thruster to deliver to a sufficient thrust for satellite station keeping with a purely electrical input and no exhaust.  Both Shawyer and Woodward are claiming micronewtons and some serious individuals have verified the results. I am now getting weight gains in the order of up to 10mg when properly stimulated on my scale, which translates to a weight loss of the piezo stack as I have a lever system that the stack is unbalancing to the milligram range on the scale, at the other end of the lever.  I am wondering if it would offer a thrust in free space? @ swansont, I thought ion thrusters were the prefered method for satellite station keeping. Are there some that would work in space?

27 minutes ago, hoola said:

@ swansont, I thought ion thrusters were the prefered method for satellite station keeping. Are there some that would work in space?

Yes; they would have to carry the reaction mass on the satellite, rather than use the Biefeld-Brown effect.

A website offers a milligram to micronewton conversion table of 50mg= 490.3325 micronewtons. If I am generating 10 mg of force, that should translate into nearly 100 micronewtons. The lever itself is a possible issue in determining what force is actually pesent. The scale is on the long end , 7   1/4" from the pivot, and the center of the stack is 1   1/2" on the other side of the pivot. The stack has 7 piezos each weighing 33.7 grams for a total of 235.9 grams. There are two heavy steel washers at the ends, of 33 grams for both. The central nylon bolt, nut and two heavy poly washers weigh 20 grams. There are six thin poly washers, each weighing 1.8 grams. This comes to a total of 294.9 grams. I  am not sure if uneven lever lengths from the pivot point, or stack weight have anything to do with measuring expressed forces. The scale is slightly overbalanced with approx 6 milligrams of weight on the scale side as a tare force.

Edited June 28, 20205 yr by hoola