why ni semiconductor in RVDT?

[jyjy]

Hi,

I just read one of our specification in which it's said that no semiconductor or semiconductor device should be used in RVDT, could anybody explain what are the reasons? thanks!

 

[ScottyUK]

RVDT as in rotary voltage displacement transducer? It has three windings with a moveable core. Output voltage on the secondary windings depends on physical position of the core. No electronics.

Demodulating the output of an RVDT (or LVDT) very probably will involve use of semiconductor devices of some form. If the transducer is going into a very hostile environment the spec may preclude use of electronics at the transducer and require demodulation be carried out away from the transducer in a less hostile location.


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[buzzp]

If it is rotary voltage displacement then it sounds like the old 'selsyns' that used to be around and still are. No semiconductor devices are needed to accurately (well pretty accurate) read the displacement of the motor shaft. This motor shaft is connected to something else to give the motor shaft its movement. The motor is energized with 120 3 phase and any corresponding movement of the shaft is sensed by the receiving motor which moves the same amount as the motor which is sensing some process (liquid level, angular movements, ..). A mechanical display can hook to this receiving motor to indicate position or whatever of the process being monitored. I believe the non trade name of such equipment is synchro. No semiconductors needed. Hope this helps.