[power4]

I want to build a very precise motion system(based on hydro/aerostatic rail),it;s a DIY project with serious budget constrain.
So I want buy a cheap system to measure parallelism of motion stages,Those sensor should be able to pick up at least 0.1u displacement.
My project still in the planning stage,I can't afford laser interferometer for such measurement.
After some googling I believe inductive displacement senor can fit my need.

system I intent to buy are used tesa or mahr inducitve displacement senor stsyem:
tesa tt 20 with a plunge typpe sensor cost 500-600 usd
or
mahr
c1298m+ plunge type sensor around 1000used
or
mahr millitron 1202+ 1302 prob 600usd
I'm very new to this kind of high preicsion metrology devices,any advice would be welcomed

[Halfnutz]

Dont forget the cost of the signal conditioning and instrumentation. Especially if your buying used, you should look for a system thats going to give you the data in the form you need it in. Finding a used sensor that requires expensive or proprietary signal conditioning could force you to buy new, and expensive, electronics.

[power4]

thanks for u advice.
numerical data telling me how stage deviate form center line or top/bottom reference surface should be enough for this job?New seneor its not that expenseive 3-500each.if I want to repalce them
What my ture conceren is the sensor signal amplifier,will they distor incomming signal give me alse positive or genative reading