Looking for a mercury-wetted reed relay that can produce nanosecond pulse

Discussion in 'General Electronics Chat' started by radetonator, Oct 8, 2011.

  1. radetonator

    Thread Starter Member

    Aug 1, 2011
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    Does anyone know which manufacturer still produces mercury wetted reed relay capable of generating 5ns high voltage pulses? Thx:)
     
  2. AlexR

    Well-Known Member

    Jan 16, 2008
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    Two questions;
    1. Why does it have to be a relay?
    2. Why 5 nSec?
    5 nSec is faster than most common logic operates at, you have no chance of finding a relay that operates that fast.
    Relays, (even reed relays) generally take milliseconds to operate. Figures for reed relays I have seen show on closure time of about 5mSec, that's 6 orders op magnitude slower that you require!
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Many logic families could have trouble producing a pulse that fast. I suspect you haven't dealt with speeds like this before, 1ns is 9 inches of travel at light speed. You would need a circuit with a minimum freq response of 200Mhz, and for a square wave it would need to be closer 2 Ghz.
     
  4. radetonator

    Thread Starter Member

    Aug 1, 2011
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    Some scholars used mercury relay to generate nanosecond pulse. It is real. I am also considering to build pulse generator based on avalanche transistor. But i think using mercury relay is the most easiest way to do it.
     
    Last edited: Oct 8, 2011
  5. Wendy

    Moderator

    Mar 24, 2008
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    Avalanche oscillators are fast by definition. Any mechanical system is not.

    I have experience with power mercury switches, for high current applications.

    You have any sources of literature for fast mechanical relays?
     
    Last edited: Oct 8, 2011
  6. crutschow

    Expert

    Mar 14, 2008
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    I assume 5ns is the rise-time of the output signal, not the operating speed of the relay (which is obviously impossible). If so, it can be done, but it requires well controlled impedance transmission line connections directly to the relay contacts. This is best done with stripline or microstrip design techniques on a controlled impedance circuit board, not a trivial task.
     
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  7. radetonator

    Thread Starter Member

    Aug 1, 2011
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    can you recommend a relay for this application?:D
     
  8. johnmcmillan

    New Member

    May 14, 2012
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    Hi. Are you still interested in this? Mercury wetted relays were used to make
    "tail pulse generators". The "Mech-Tronics 1000 mercury relay pulse generator"
    and the "Ortec 480 Pulser" are both examples in NIM format. They give a pulse risetime
    (or fall) of a nanosecond or so followed by a slow recovery. By building simple RC
    circuits you can produce 5ns width pulses easily. I had a Mech-Tronics 1000 fail a few
    years ago - but repaired it with the exact relay it was built with which I got from some surplus house. Most manufacturers don't like mercury anymore - but there are plenty from Clare, western electric etc on the surplus market. You can build nanosecond electronics without stripline - but you need to be careful. If you're still interested, I can look out the exact relay type.
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    This thread is months old so I doubt if there is any follow up.
     
  10. P-MONKE

    Member

    Mar 14, 2012
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    As we're here - the speed of light in a vacuum is closer to 1 foot per nano second - it's a physicists rule of thumb.

    Not trying to be a smart-arse, just increasing the collective knowledge. ::ducks down behind desk:: ;)
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    My rule of thumb is 3ns per metre - same difference.
     
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