[PSES] How to Measure Surface Conductivity?

[Brian Kunde]

I have been given two samples of metal plates; one plated in our current
material and the other with a new plating material we want to switch to in
production.  I have been tasked to compare the electrical surface
conductivity.

What is the best way to do this?  How is this done in the industry?

I have tried the following methods;
1. DMM (Ohm Meter) = inconclusive results
2. Used 5 volts from a current limited power supply and measured the
current = inconclusive results
3. Used our Ground Bond Tester set to 60 amps. One plate measured 3-4mΩ,
the other 1-3mΩ

I measured 1 inch apart and from corner to corner. Test #3 above is the
only test that showed any difference.

BTW, I use 3/4" squares of soft braid material between the probes and
surface. The probes are zeroed out between tests.

So far, I can conclude that the new material is as good as, or slightly
better than our current production plating material.

What more can I do, within reason?

Thanks to all.
The Other Brian

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Re: [PSES] How to Measure Surface Conductivity?

[Marko Radojicic]

Try a conductive elastomer on the DMM probes. Intent is to not scratch the surface. However from your description, new coating appears functionally equivalent especially if bonding mechanisms use any type of sharp edge (BeCu gasket, screw, etc)Sent from my mobilePlease excuse brevity & grammar On Apr 11, 2023, at 12:45 PM, Brian Kunde  wrote:I have been given two samples of metal plates; one plated in our current material and the other with a new plating material we want to switch to in production.  I have been tasked to compare the electrical surface conductivity.What is the best way to do this?  How is this done in the industry?I have tried the following methods;1. DMM (Ohm Meter) = inconclusive results2. Used 5 volts from a current limited power supply and measured the current = inconclusive results3. Used our Ground Bond Tester set to 60 amps. One plate measured 3-4mΩ, the other 1-3mΩI measured 1 inch apart and from corner to corner. Test #3 above is the only test that showed any difference.  BTW, I use 3/4" squares of soft braid material between the probes and surface. The probes are zeroed out between tests.  So far, I can conclude that the new material is as good as, or slightly better than our current production plating material.  What more can I do, within reason?Thanks to all.The Other Brian
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Re: [PSES] How to Measure Surface Conductivity?

[Ken Javor]

I would measure ohms per square using a milliohm meter. Also, another
critical parameter is how hard the coating is. If the new coating is much
harder than the original, it will likely make for poorer conductivity at any
seams, resulting in lower shielding effectiveness even if the material
conductivity is similar.  A gasket might then be required where none was
previously.

Marko Radojicic¹s comment bears directly on this issue.  The connection
between probes and coatings should be identical, including applied pressure.
If more pressure needs to be applied to get good results, that is a measure
of the surface hardness.

Ken Javor
Phone: (256) 650-5261




From: Brian Kunde 
Reply-To: Brian Kunde 
Date: Tue, 11 Apr 2023 15:45:29 -0400
To: 
Subject: [PSES] How to Measure Surface Conductivity?

I have been given two samples of metal plates; one plated in our current
material and the other with a new plating material we want to switch to in
production.  I have been tasked to compare the electrical surface
conductivity.

What is the best way to do this?  How is this done in the industry?

I have tried the following methods;
1. DMM (Ohm Meter) = inconclusive results
2. Used 5 volts from a current limited power supply and measured the current
= inconclusive results
3. Used our Ground Bond Tester set to 60 amps. One plate measured 3-4m‡, the
other 1-3m‡

I measured 1 inch apart and from corner to corner. Test #3 above is the only
test that showed any difference.  

BTW, I use 3/4" squares of soft braid material between the probes and
surface. The probes are zeroed out between tests.  

So far, I can conclude that the new material is as good as, or slightly
better than our current production plating material.  

What more can I do, within reason?

Thanks to all.
The Other Brian
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[PSES] Fw: Re: [PSES] How to Measure Surface Conductivity?

[Brian Gregory]

 Conductive epoxy bonding the probe to the surface?Calibrate with a current 
shunt. "Colorado" Brian 
720-450-4933

-- Forwarded Message --
From: Marko Radojicic <052300254e41-dmarc-requ...@listserv.ieee.org>
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] How to Measure Surface Conductivity?
Date: Tue, 11 Apr 2023 13:00:08 -0700


Try a conductive elastomer on the DMM probes. Intent is to not scratch the 
surface. 
 However from your description, new coating appears functionally equivalent 
especially if bonding mechanisms use any type of sharp edge (BeCu gasket, 
screw, etc)

Sent from my mobilePlease excuse brevity & grammar 
On Apr 11, 2023, at 12:45 PM, Brian Kunde  wrote:

I have been given two samples of metal plates; one plated in our current 
material and the other with a new plating material we want to switch to in 
production.  I have been tasked to compare the electrical surface conductivity. 
What is the best way to do this?  How is this done in the industry? I have 
tried the following methods;1. DMM (Ohm Meter) = inconclusive results2. Used 5 
volts from a current limited power supply and measured the current = 
inconclusive results3. Used our Ground Bond Tester set to 60 amps. One plate 
measured 3-4mΩ, the other 1-3mΩ I measured 1 inch apart and from 
corner to corner. Test #3 above is the only test that showed any difference.   
BTW, I use 3/4" squares of soft braid material between the probes and surface. 
The probes are zeroed out between tests.   So far, I can conclude that the new 
material is as good as, or slightly better than our current production plating 
material.   What more can I do, within reason? Thanks to all.The Other Brian-
 
This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 

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 List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
 Mike Cantwell 
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 Jim Bacher 
 David Heald 
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[PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles

[Dürrer Bernd]

Hello James,

Thank you for providing this additional information and the sketch. My 
conclusion that the handles are a class II construction was based on your 
statement in your original post that the handles are not "reliably earthed". As 
I understand now from your additional information they are not earthed by a 
dedicated wiring to the protective earthing conductor, but incidentally the 
measured resistance complies with the requirements of IEC 60335-1, clause 27.5. 
Please remember that the protective earthing connection shall be reliable over 
the whole lifetime of the appliance. Apart from wear and grease build up that 
you already mentioned you should check whether the parts providing the 
connection comply with clauses 27.4 (corrosion) and 28 (screws and connections).

With respect to the question whether the requirements of clauses 22.35 and 
22.36 also apply to handles of a class I appliance that are reliably earthed 
(and therefore are not a class II construction), I recommend to check the 
decisions of TC 61 that are published at IEC - TC 61 Dashboard > Documents: 
Working Documents, Other Documents, Supporting 
Documents:
 I have found decisions on the interpretation of clause 22.35 in the archives 
"TC 61 Inquiries 2011 and previous" 
(https://assets.iec.ch/public/tc61/2011%20and%20previous%20Inquiries.zip?2023041235)
 and "TC 61 Inquiries 2015" 
(https://assets.iec.ch/public/tc61/2015%20Inquiries.zip?2023041235). It seems 
that the committee's view is that these clauses are applicable to class I 
constructions. However, as defined in the second paragraph of clause 22.35, 
stationary appliances are exempt if their handles are reliably earthed.

Kind regards,

Bernd

Von: James Pawson (U3C) 
Gesendet: Dienstag, 11. April 2023 12:22
An: EMC-PSTC@LISTSERV.IEEE.ORG
Betreff: Re: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or 
not) of handles

[EXTERNAL E-MAIL] This email originated from outside of the organization. Do 
not click links or open attachments unless you recognize the sender.
Thank you to everyone who has replied to this query so far, your thoughts were 
very helpful in refining my thinking.

To give some further context (some of which I should have provided earlier)


  1.  The appliance is stationary and of class I construction
  2.  The handles are held continuously in normal operation
  3.  For a basic overview of construction please see the attached sketch (or 
this 
link
 if the email reflector eats the attachment)
  4.  Whilst the grips are foam, it is light/porous in nature (not good enough 
for Supplementary insulation) and it would be very easy for the user to hold 
the metal instead
  5.  We made some earth bonding resistance measurements on the equipment. The 
handles are not explicitly earthed (via a Protective Bonding Conductor) but the 
contact to the metal frame through the bearings and shafts (not shown on 
sketch) gives a resistance of approx. 40mR @ 25A even under motion of all 
joints. We have not accounted for any wear, grease build up, etc)

My views:


  1.  I agree with the below discussions - it feels like the standard could 
benefit from a wording change for clause 22.35 and 22.36 with each clause 
starting "For class II constructions, [...]"
  2.  The construction of the appliance, and lengths of wiring involved, means 
that if the Basic insulation fails (see 60335-1 Class I definition below) then 
there is a very low likelihood of the handles becoming live. The wires will 
only contact the earthed frame instead. At the moment, I don't agree that the 
handles would form a class II construction as protection is still provided by 
Basic + Earthing (but I'm willing to be persuaded by a convincing argument)

3.3.9 class I appliance
(basic plus earthing) in such a way that conductive accessible parts cannot 
become live in the event of a failure of the basic insulation


  1.  The low resistance of the incidental bearing connection is further 
mitigation against having to explicitly earth the handles
  2.  If live wiring or basic insulated wiring is routed anywhere near the 
handles on different versions of the appliance then they will need an explicit 
earth connection
  3.  I'm sure the standards committee had a specific case in mind when they 
wrote these clauses, I just wish there was an explainer document like EN 
62368-2!


Again, with thanks.
All the best
James

James Pawson
Managing Director & EMC Problem Solver

Office hours:
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