wrist strap tester

tnuflora said:

hi..
i'm really interested in that.
And i have checked the given ckt. that was really nice.but that is not suitable to use in an industry.

thnx

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JimB said:

The why not just BUY ONE!

Spend some money.

JimB

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ericgibbs said:

hi tnuflora,
Look at the attached pdf.
The design has been built and checked OK, using loop resistances of 330K thru 1M0 and a short circuit loop.

You will understand, as I will not be the person building and using this unit I will not be held responsible
for any damage or injury that may result from using this design.

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tnuflora said:

thnx..................

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tnuflora said:

hi eric,


i was working with the circuit that u have given.
In that safe operation is working fine.but
fault condition is not at all indicating.
can u give some more details about the working of the circuit ?

Click to expand...

ericgibbs said:

hi,
Pleased to hear the tester is OK.

Regarding the Fault, this LED will light if the high value resistor has been removed from the strap and a link used to replace the resistor.

In other words its a strap with no series protection resistor, which is UNSAFE.

I have seen instances where the wire with the resistor has broken away from the wrist strap, due daily use, and the user has connected just a piece of wire to the strap, which is a bad idea.

OK.

Click to expand...

tnuflora said:

hi,
sorry, i mean ,even if i removed the high value resistor then also the fault LED is not glowing.

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ericgibbs said:

hi,

Are you completing the circuit by touching the 'test probe' to the earthing stud of the wrist strap.?

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tnuflora said:

hi,

i just removed the high value resistor.

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ericgibbs said:

Did you replace the removed resistor with a wire link.?

The purpose of the Fault LED is to check a wrist earthing strap thats made without the high value resistor..

On this attachment I have marked the connections points more clearly.

Click to expand...

ericgibbs said:

Did you replace the removed resistor with a wire link.?

The purpose of the Fault LED is to check a wrist earthing strap thats made without the high value resistor..

On this attachment I have marked the connections points more clearly.

Click to expand...

tnuflora said:

hi,

i've a question...if the strap is made with a high value resistor & for some reasons it fails,how the circuit will respond to it?

i mean , the connection to the gnd will be disconnected & it will be an open ckt. w'll the red LED glows ?.

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ericgibbs said:

If the resistor is too high a value or open circuit the Green 'PASS' led will not light.

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tnuflora said:

hi..

i need to know abt the red LED at that condition.

Click to expand...

hi,
Pleased to hear the tester is OK.

Regarding the Fault, this LED will light if the high value resistor has been removed from the strap and a link used to replace the resistor.

In other words its a strap with no series protection resistor, which is UNSAFE.

I have seen instances where the wire with the resistor has broken away from the wrist strap, due daily use, and the user has connected just a piece of wire to the strap, which is a bad idea.

OK.

Click to expand...