How do ESD monitors work?

[zibilytou]

Hi everyone,
I want to understand how do ESD monitors work, those that detect if someone is wearing an ESD wrist strap or not and give signals to remind you to wear it. Well i know many methods but all of them work with the dual wire wrist band, therefor it is not hard to detect a person with two wires feedback. But the problem is that i need to work with the one wired wrist band and i don't know how can you measure anything from just one wire.
I've read that the human body acts like a capacitor forming an RC circuit when wearing the wrist band and if you run some tiny AC current through this circuit, there will be a displacement current.
But still i can't figure out how can you use this information to detect if someone is wearing the wrist band or not.

 

[shrtrnd]

ESD straps are to ground the user, draining away static build-up on the person wearing it.
An ESD monitor is designed to tell the wrist-band wearer when he/she is not grounded.

 

[zibilytou]

ESD straps are to ground the user, draining away static build-up on the person wearing it.
An ESD monitor is designed to tell the wrist-band wearer when he/she is not grounded.

Yeah that is the main purpose of an ESD monitor i know, but it also detects if someone is wearing the writs-band or not and that is what i seek to understand.

 

[Harald Kapp]

It is done by measuring the resistance between the person touching the sensor plate and ground.
A properly ESD protected person has a certain minimum resistance > 1 × 10^5 Ω but also a certain maximum resistance < 1 × 10^9 Ω (reference taken from here).

 

[zibilytou]

It is done by measuring the resistance between the person touching the sensor plate and ground.
A properly ESD protected person has a certain minimum resistance > 1 × 10^5 Ω but also a certain maximum resistance < 1 × 10^9 Ω (reference taken from here).

Hello sir, there is no sensor plate, i think you are talking about something else, here's an example of monitor

 

[Harald Kapp]

No sensor plate: yes
Same prociple: yes.
See the short explanation here:

Continuously monitors the path-to-ground integrity of two operators and one conductive or dissipative worksurface; meets ANSI/ESD S20.20 in accordance with ESD TR1.0-01-01.

 

[shrtrnd]

zibilytou, I believe you are asking a basic question(?)
Why the ESD monitor alert energizes.
If you are wearing the wristband, or touch the wristband to a ground, no alarm. (Because the wristband is grounded)
If you are not 'grounded' while wearing the wristband, or the wristband is not touching a ground, you get an alarm.
I think Harald Knapp directed you to good information if you are asking a more specific technical question here about HOW
the ESD monitor works.
The monitor is designed to indicate whether or not your body is 'grounded' to drain any static electricity from you, so that you
can be reasonably certain any static charge that might otherwise be present, is not there, so that charge doesn't damage any
ESD sensitive electronic component you come in close contact with.
If you are asking about the technical design of the ESD monitor, and how it works, hopefully Harald Kapp's information answered
your question.

 

[zibilytou]

zibilytou, I believe you are asking a basic question(?)
Why the ESD monitor alert energizes.
If you are wearing the wristband, or touch the wristband to a ground, no alarm. (Because the wristband is grounded)
If you are not 'grounded' while wearing the wristband, or the wristband is not touching a ground, you get an alarm.
I think Harald Knapp directed you to good information if you are asking a more specific technical question here about HOW
the ESD monitor works.
The monitor is designed to indicate whether or not your body is 'grounded' to drain any static electricity from you, so that you
can be reasonably certain any static charge that might otherwise be present, is not there, so that charge doesn't damage any
ESD sensitive electronic component you come in close contact with.
If you are asking about the technical design of the ESD monitor, and how it works, hopefully Harald Kapp's information answered
your question.

But the major problem remains ambiguous, the ESD monitor has to ground the human body through the wrist band for sure, but when the wire is plugged in, how does the monitor know and stop signaling the alarm ? that is what i seek to understand. And as mentioned in the attachment file above you can run a tiny current through the wire, but still i can't figure out how is that useful.

 

[shrtrnd]

Alright, sounds like you're asking the technical question about how the ESD monitor circuitry tells the user the wristband is properly grounding the user. (The monitor stops signaling the alarm).
Refer to Harald Kapp's previous post at 5:17am 16APR20.
People ask for free information here, and members of this forum offer free information at no charge, because we're nice.
If somebody responds to our answers with irritability, we generally tell them to recheck the information we supply, AND GO
LOOK THE INFORMATION UP YOURSELF.
Have a nice day, we generally try to.
*steve* go ahead and delete me ...again.

 

[Harald Kapp]

but when the wire is plugged in, how does the monitor know and stop signaling the alarm ?

There are a few possibilities, the simplest one being a switch built into the socket that detects when a plug is inserted and arms the monitor. The monitor then measures the resistance as I have described.

 

[zibilytou]

Alright, sounds like you're asking the technical question about how the ESD monitor circuitry tells the user the wristband is properly grounding the user. (The monitor stops signaling the alarm).
Refer to Harald Kapp's previous post at 5:17am 16APR20.
People ask for free information here, and members of this forum offer free information at no charge, because we're nice.
If somebody responds to our answers with irritability, we generally tell them to recheck the information we supply, AND GO
LOOK THE INFORMATION UP YOURSELF.
Have a nice day, we generally try to.
*steve* go ahead and delete me ...again.

Oh i was enjoying the discussion in this forum and how the members don't hesitate to help and respond to questions until i read your post. I did not break any rule and tried to be as interactive as possible. When someone misunderstands your question you don't just ignore them, you try to clarify your point so that everybody understands even if they don't have an answer, because the whole point of this forum is to spread knowledge as far as i know, to us members and to foreign visitors seeking information.
You assumed that i am just searching for cheap information and i do not check the posts of people who try to help and you acted based on that assumption. Believe me i read every single line written or shared by anyone because it would be rude not to do so and because i understand that people give their precious time trying to help. But as i said earlier, i should clarify my point to to them so that their time wont go wasted.
If you are having a bad day sir, please try not to let that affect the way you talk to people, because you could really hurt someone's feelings.
Thank you and have a nice day.