Vintage electrical tech - Weston Sensitrol Relay-----make money online

today on Applied Science we're going to

take a quick look at some neat vintage

test equipment and these shorter videos

will be freebies for my patreon

subscribers so take a look at this this

is a Westin sensitive a and basically

it's an analog meter with latching

contacts on either side so let me show

you what I what it does if you put a

tiny amount of current into the meter

you can see the needle moves and then if

you have a very large current it

actually swings the needle over to one

end and there's a magnet that holds it

there and latches a relay contact pretty

cool what's especially unusual about

this is that it's so sensitive just two

and a half micro amps is it's sensing

range and it's also bi-directional now

you might also be wondering how do we

reset it I mean it's latched now and

there's no lever here to undo it there's

a solenoid in the back so I'm going to

turn on another power supply and it

pulls the needle back to Center

with these two little rubber fingers

that actually pull the needle back to

Center and so now I'll put the magnet in

slowly this time and then withdraw it

quickly and it swings to the other side

and latches the other contact pretty

cool here's a close-up so you can see in

an action and I'm just using the magnets

in the coil again very sensitive and

then you can see it latch over just like

that and here's the action of the

centering device see it kind of pulling

in there to show how sensitive this

thing is I thought of some other stuff

to connect to it and so in this case

I've connected a white LED right up to

the meter and if I shine an ultraviolet

light on it it produces enough current

to make the thing swing over and there's

a little bit of a time effect too so if

at close range if you swing quickly sort

of nothing happens but if you hold over

it then it has enough time to move the

needle of the meter and so it has this

sort of automatic averaging effect

whereas if you were going to recreate

this with modern technology you know

you'd use a microcontroller and some

averaging and maybe filtering of all

kinds but the actual physical momentum

of the needle actually provides all

these

things inherently which is pretty cool

another way to trigger these LEDs is to

just hit it with a 405 nanometer laser

pointer and this will really do it

quickly and finally I've just got a

strip of magnesium metal here which is

very electrically active it has like a

high electrical potential and so just

hanging onto it with my fingers and then

touching the other lead is enough to get

two and a half micro amps and if I kind

of blow on my fingers a little bit so

they're a little more moist it's enough

to trigger the meter the speeder is in

really good condition I found it at a

local surplus store and it appears to be

new old stock never installed it's got a

1957 date code and the the brass

terminals aren't really corroded at all

the things been stored really well

appears to be in near perfect condition

I've even got the tag for it and I'll

put a link in the video to an old

advertisement a period advertising piece

so let's connect this up to the source

meter so we can see how what the coil

resistance is in the previous setup I

was using this source meter to supply

the voltage for the reset solenoid in

the sense of troll and the reason is

that that solenoid is designed for 115

volts ac I didn't really want to connect

it up to the wall so I was using the

source meter to supply about 60 volts DC

which was enough but now I have the

source meter connected up to the actual

coil in the meter so we can see how it

performs so if I turn the source meter

on it's drawing 1 micro amp at 2.3

millivolts and if I turn it on and off

and you look over at the meter you can

see it is in fact moving about right

it's about half halfway to its red mark

there so now we'll turn this up to about

2 micro amp and again the meter agrees

with that let's keep going

2.5 micro pretty much right at the

redline about 3 micro

and three is enough to trip the meter it

just swung over and hit the magnets on

the end so at three microamp it's

drawing 6.5 millivolt if my math is

correct this is only eighteen nano watts

of power so it's pretty cool to get a

real a contact closed with just 18 nano

watts of Sense power it's actually a

fairly unique device even with modern

technology there's nothing that works

quite like this okay well I hope you

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