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Re: ESD mats portable set for safe soldering - field test

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  • Petr
    Hi Geoff, thank You very much for Your comment regarding the ESD mats. In fact I did not measured it for the first time because I had not any appropriate
    Message 1 of 5 , Aug 1, 2012
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      Hi Geoff,

      thank You very much for Your comment regarding the ESD mats.

      In fact I did not measured it for the first time because I had not any appropriate probes available to make serious measurement.

      According to Your kind comment I called to my friend who is working in industrial corporation and he allowed me to use their professional surface resistivity tester with actual calibration certificate.

      Measured in harmony with IEC 61000 standard I tested this ESD mat and with 6cm distance measured the resistivity of 12.1x10^6 ohms which corresponding to better than 10^7 ohms. It seems to be perfect result as the suppliers datasheet is talking about the 10^6 to 10^8 ohms range.

      So finally I am really happy for purchasing it and hope it really help in order to protect ESD-sensitive circuits or parts when handling or soldering etc.

      73 - Petr, OK1RP


      --- In softrock40@yahoogroups.com, Geoff Blake <geoff@...> wrote:
      >
      > Hi Petr, Group,
      >
      > First posting to this group, so please be kind to me. Petr, you seem
      > to have missed measurement ofone of the most important parameters of
      > an anti-static mat, and that is the surface resistivity, measured in
      > the slightly enigmatic "ohms per square."
      >
      > The surface resistivity, which used to be in the range of 10^4 to 10^8
      > ohms when I was involved some 20 years back, may be measured by the
      > parallel placing of two conductive bars, 2cm square by 6cm long with a
      > 6cm spacing between them. Ideally they should have a downward pressure
      > of around 1.25kg on each bar. Ideally, the measurement should be made
      > with a relatively high voltage source of between 100 to 500Vdc
      >
      > For those who have access, all this is covered in the IEC 61000 series
      > of documents IIRC.
      >
      > Hope this helps.
      >
      > Geoff
      >
      >
      >
      > --
      > #################################################
      > Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
      > <geoff@...> or <melecerties@...>
      > Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
      > and even on the NAS. Avoiding Micro$oft like the plague.
      > #################################################
      >
    • Geoff Blake
      Hi Petr, Group, Since I emailed you, I noticed a typo, the surface resistivity probe bars were 1cm square.not 2cm. In our home-made unit the bars were attached
      Message 2 of 5 , Aug 2, 2012
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        Hi Petr, Group,

        Since I emailed you, I noticed a typo, the surface resistivity probe
        bars were 1cm square.not 2cm. In our home-made unit the bars were
        attached to a PTFE back plane which had an attached steel block to
        provide the necessary contact pressure.

        I have been delving deeper in my memory regarding surface resistivity
        and another couple of points came to mind. The values of surface
        resistivity, particularly the lower values, were only for the assembly
        process. Use of low value mats on powered equipment could present a
        risk to the operator, especially on equipment using higher voltage
        supplies.

        Secondly, the mat should be "earthed" to a "common reference point"
        via a 1Mohm resistor and the value of the surface resistivity to this
        reference point checked to be in the same order as the surface
        resistivity. The "common reference point" should itself be earthed to
        a true earth via another 1Mohm resistor.

        Finally, the wrist strap should also be connected to the "common
        reference point" via a resistive lead, generally of the yellow curly
        type. The resistance of the lead and wrist strap should be checked to
        be within the range 700kohm to 35Mohm by a suitable go-nogo
        low-voltage tester to which the end of the lead attached to a suitable
        connector and finger pressure to a contact completed the circuit.

        I didn't say previously but in the early 1980's I wrote the
        "procedures" regards ESD safe areas and the testing thereof for a
        major UK company. I no longer have access to them and it was a long
        time ago. The goal posts were frequently moved, and no doubt have been
        moved several times since - however the principles remain the same.

        Finally, this was all a long time back and my memory isn't perfect.
        However, I do have a ESD workstation in the shack and so test it from
        time to time.

        Geoff

        On 2 August 2012 00:27, Petr <indians@...> wrote:
        > Hi Geoff,
        >
        > thank You very much for Your comment regarding the ESD mats.
        >
        > In fact I did not measured it for the first time because I had not any appropriate probes available to make serious measurement.
        >
        > According to Your kind comment I called to my friend who is working in industrial corporation and he allowed me to use their professional surface resistivity tester with actual calibration certificate.
        >
        > Measured in harmony with IEC 61000 standard I tested this ESD mat and with 6cm distance measured the resistivity of 12.1x10^6 ohms which corresponding to better than 10^7 ohms. It seems to be perfect result as the suppliers datasheet is talking about the 10^6 to 10^8 ohms range.
        >
        > So finally I am really happy for purchasing it and hope it really help in order to protect ESD-sensitive circuits or parts when handling or soldering etc.
        >
        > 73 - Petr, OK1RP
        >
        >
        > --- In softrock40@yahoogroups.com, Geoff Blake <geoff@...> wrote:
        >>
        >> Hi Petr, Group,
        >>
        >> First posting to this group, so please be kind to me. Petr, you seem
        >> to have missed measurement ofone of the most important parameters of
        >> an anti-static mat, and that is the surface resistivity, measured in
        >> the slightly enigmatic "ohms per square."
        >>
        >> The surface resistivity, which used to be in the range of 10^4 to 10^8
        >> ohms when I was involved some 20 years back, may be measured by the
        >> parallel placing of two conductive bars, 2cm square by 6cm long with a
        >> 6cm spacing between them. Ideally they should have a downward pressure
        >> of around 1.25kg on each bar. Ideally, the measurement should be made
        >> with a relatively high voltage source of between 100 to 500Vdc
        >>
        >> For those who have access, all this is covered in the IEC 61000 series
        >> of documents IIRC.
        >>
        >> Hope this helps.
        >>
        >> Geoff
        >>
        >>
        >>
        >> --
        >> #################################################
        >> Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
        >> <geoff@...> or <melecerties@...>
        >> Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
        >> and even on the NAS. Avoiding Micro$oft like the plague.
        >> #################################################
        >>
        >
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >



        --
        #################################################
        Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
        <geoff@...> or <melecerties@...>
        Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
        and even on the NAS. Avoiding Micro$oft like the plague.
        #################################################
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