Technical Details (24 Aug '20)

More info please!

Many of you were asking for greater detail on the issue we faced during verification testing of Pokit Pro. Well, here you go!

First off - if you haven't read the last update yet, we suggest you do that first. It provides the necessary background for the technical details below. Also, please note that this issue has now been solved! We're excited about moving forward and are thankful for your support and patience in this.

The Juicy Details

In order to allow for Pokit Pro to be as small as possible, we have taken a general approach in which we’ve opted to remove as many physical switches as possible from the device. This is quite a contrast to conventional measurement tools, such as a multimeters, which tend to have a lot of switches and plugs. Being compact is what makes Pokit Pro (and Pokit Meter) so special.

With size in mind, we used a MOSFET to switch in the 10A sense resistor for the Pro's 10A mode. During compliance testing, we discovered a failure mode whereby: 1) if the device was in the 10A current sense mode, and 2) was left on for an extended period of time, and 3) if the battery happened to run flat…the FET switch could not remain on, causing the device to open circuit.

Although clamping diodes were used to limit voltage across the FET, when the device measured a large current within the fuse rating, excessive heating of the device would occur. This heating was a safety risk and was one we were not prepared to take.

How we solved it

The Pokit team put our heads together and looked at a number of solutions. This included using high voltage FETs, however, these were too large to fit within the device. We also assessed the possibility of using lower voltage clamping diodes to reduce the associated heating, but all such devices have higher leakage currents which interfere with the current sensing.

In the end, we decided to separate the 10A mode completely by adding an additional fuse and a physical switch (so much for the switch avoidance!). It was quite a challenge to devise a switch configuration that was robust and compact, but we're proud to say we achieved it with only a 3mm increase in product length!

The new Pokit Pro design is currently undergoing prototyping, verification, and certification.

In the meantime, production component purchasing is continuing to proceed in parallel as there are very few parts changes.

We hope this information helps to answer your questions! Please rest easy knowing that Pokit Pro is in experienced hands, and that we don’t compromise when it comes to safety and quality.

Thank you all for your feedback, and we hope to hear back from you so we can continue to improve the way we do things.