On 26 May 2006, at 15:03, Steven Howes wrote:

> Hi, I was wondering if anyone here could work out why a 1A reed relay
> would 'stick' when carrying only 700ma.. It is only a low voltage (ie 2
> or 3 v) so it is unlikely to be a power issue. The reed relay in
> question is an RS Electronics 291-9710. They appear to stick randomly
> then sometimes unstuck which seems a little odd. Is it possible that
> they were damaged during soldering?
No.
They always have stuck - a well-known company produced data-loggers 
incorporating reed switches for switching very low voltages (from 
thermocouples etc). The reeds were always sticking randomly after a few 
thousand operations (not very long at up to 100 channels per second). This 
caused all sorts of problems as thermocouples would get jpined to others at 
different "chassis" potentials. There was no cure so we (the service guys) just 
had to carry a large stock of the damned things and replace all of them ( 4 per 
channel and up to 500 channels) at once. If we just replaced the faulty one 
then we could expect another call a few days later...
These were high quality reeds. Cold welding was the given answer.

George

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