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Bad News

I hate to be the bearer of bad news, but we ran into a problem.

When I announced that we passed our electrical tests, I spoke too soon.  On closer read of the 61010-2-030 spec we discovered that one of the tests had been run incorrectly.  Under the new conditions, it no longer passes.  Here is the quick summary, details are below:

  1. There will be a shipping schedule delay. We will announce the new official date once we confirm it through the entirety of the affected supply chain.
  2. The SD Card slot needs to be closed.  Removing the SD card will now require a screwdriver.

Thank you for your understanding.  Safety is our first priority, and we will ship safe Mooshimeters.

The Test

The test in question is the housing dielectric test.  This test ensures the safety of the user when the device is held in a user’s hand and a voltage surge occurs.

We initially ran this test at standard room temperature and humidity, and passed.  However, that test needs to be run after humidity preconditioning.  The device is held at 42C and 93% relative humidity for 48 hours to allow any hygroscopic materials to absorb water.  It is then allowed to rest for 2 hours at STP before being subjected to the dielectric tests.

Without the humidity preconditioning, the Meter passes the test without issue.  With preconditioning, the condensed moisture along the inside of the housing provides a conductive path through the SD card slot.  This reduces the effective creepage and clearance distance to the point where it can no longer effectively block the 5400VAC RMS (~7600V peak).

Solutions:

Unfortunately, the SD card is already as far back as it can be and still be accessible when it is ejected.  Further increasing the spacing would increase the voltage it could withstand, but it would defeat the purpose of the slot.

This leaves us with two options:

  1. Reduce the rating of the meter from CAT III 600V to either CAT II 600V or CAT III 300V.  This would reduce the test voltage and allow the meter to pass unmodified.
  2. Close the slot.  This increases the clearance distance substantially and places 2mm of polycarbonate in the way.

We have to decided to move forward with the second option: It safely maintains all promised functionality, at the cost of reduced convenience while data-logging.

Schedule:

Other aspects of the project are proceeding as planned.  The cases and leads have been manufactured and are on a boat headed this way.  The PCBs are in production.

The mold for the housings needs to be reworked.  The modified housing will be back in the test lab Monday – assuming a pass, the injection molding manufacturer will modify the mold to add a plastic lip that seals the slot for the SD card.

 
Molds ready for modification

3 Responses to “Bad News”

  1. Seth July 23, 2014 at 9:31 am #

    Bummer about the failed testing :( Are we going to need to open the entire unit up to get to the SD card now, or will there just be a door covering the slot?

    • Eric VanWyk July 23, 2014 at 11:11 am #

      Unfortunately, the standard is written such that anything (such as a door) that can be removed without a tool is placed in the worst position possible during testing. That means that a door or flap would not help us pass the test.

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  1. Testing Completed for 61010-1 and 61010-2-030 | Mooshim Engineering - July 31, 2014

    […] I said in my earlier post, we had issues with the housing dielectric withstand test, which is the set of tests to verify that […]

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