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Guru
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Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/08/2015 2:55 AM

What is the non-hazardous replacement for bounce free mercury wetted relays?

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Prof. (Dr.) Shyam, Managing Director for Sensors Technology Private Limited. Gwalior, MP474001, India.
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Guru
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#1

Re: Non-hazardous replacement for bounce free mercury wetted relays

10/08/2015 3:51 AM

Would a sub-miniature toggle switch do (rhetorical question - NNTR)?

Without some parameters, the prospect of a valid and worthwhile response from any reader would seem a little unlikely.

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Guru

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#2

Re: Non-hazardous replacement for bounce free mercury wetted relays

10/08/2015 4:14 AM

Seems some basic research needs to be done!

https://en.wikipedia.org/wiki/Mercury_relay

Has a nice answer to your question!

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Guru

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#3

Re: Non-hazardous replacement for bounce free mercury wetted relays

10/08/2015 5:20 AM

I agree with IdeaSmith: is there a reason why you shouldn't go solid state?

See my posts 7 & 37 and Redfred's post 9 in this thread for a circuit to ramp the power on the output of a FET switch.

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Guru
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#7
In reply to #3

Re: Non-hazardous replacement for bounce free mercury wetted relays

10/09/2015 10:36 PM

Hi Randall:

Yes, I do use solid state switches but they have many problems. 1) large leakage current. 2) High switch resistance. 3) Limited operating voltage and current handling capacity. One great advantage of solid state switches is the speed we get from them and measurement can be accelerated.

Electro-mechanical switches have nearly 10^12 to 10^14 open resistance which makes them truly isolated. Mercury contacts are bounce free and are often great for nuclear pulsers and many applications where speed of measurement get accelerated due to zero bounce.

I am not sure if anything else can replace Mercury. Perhaps some conductive nano-fluid may help.

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Guru

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#4

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/08/2015 10:10 AM

It depends on the voltage type (AC or DC), the physical footprint limitations, and the amount of current being interrupted in the circuit.

It may be possible to utilize TRIAC modules if high speed switching is not required.

FET or SCR components may be feasible.

Vacuum relays are yet another option.

I suggest you contact several relay suppliers and discuss the application with their application engineer(s) so that a viable alternative specific to your needs can be identified.

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Guru
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#8
In reply to #4

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/09/2015 10:37 PM

Hi SHOCKHISCAN:

Mercury wetted relays are only for bounce free signal switching and rarely for power switching.

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Guru
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#5

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/08/2015 1:38 PM

Also a standard mechanical relay with an additional electronic debounce circuit may be suitable. Not the best option but just putting it out there as another possible option.

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Guru

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#6

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/09/2015 6:08 AM

What is your application Syam?

Last time I encountered a mercury wetted relay was in a telex exchange a long time ago. The need for these, in this application, was eliminated by progress. I saw transistors and then ICs keep the legacy alive but we've moved on from 75 Baud and morse.

What's it for mate?

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Guru
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#9
In reply to #6

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/09/2015 10:43 PM

Hi Wal:

Application is large array of signal multiplexer with low contact resistance, high isolation resistance, bounce free switching. I usually have Femto Amps to Nano Amp signals. Switching solid state is not feasible.

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Guru

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#10
In reply to #9

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/09/2015 11:14 PM

A mercury wetted relay is not hazardous if the the enclosure isn't breached.

Their operation is non hazardous.

You could have a dual containment system to be super safe eliminate some hazard.

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Guru
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#11
In reply to #10

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/10/2015 12:33 AM

Hi Wal:

Hazardous is in the sense of disposal after becoming waste material. As long as they are working, they are alright to be used.

Mercury spilling into environment is pretty dangerous.

Technology developers are now more concerned about disposal of used up electronics, which is getting piled up in the hands of non-technical people who can't differentiate them.

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Guru

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#12
In reply to #11

Re: Non-hazardous Replacement for Bounce Free Mercury Wetted Relays

10/10/2015 3:47 AM

These relays are not common consumables and it wouldn't be unreasonable to expect the end user, who would not be an ignorant, common consumer, to store and/or properly dispose of this particular ewaste.

If a non mercury alternative to mercury wetted relays became available then the sudden glut of mercury wetted relays in the mad rush to dehazardisation could overwhelm the proper storage and disposal systems in place. The solution to a hazard could seed a disaster it was intended to avert.

Mercury in the environment is not good. It is also not absent. Just saying.

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Users who posted comments:

IdeaSmith (1); jack of all trades (1); PWSlack (1); Randall (1); SHOCKHISCAN (1); Shyam (4); Wal (3)

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