Since our March update we have overcome the biggest single issue we have faced: creating a custom thermocouple connector. It was wonderfully challenging and our team has learned quite a bit. As soon as we have our 10,000 piece order in stock you will be able to purchase the Pax Instruments surface mount thermocouple connector in our store.

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3D rendering of the thermocouple connector

Here is a quick rendering of the connector. It is very simple, but it was loads of work to get here. Finding the right balance between all the variables was an adventure.

The solution space is actually not very large once we applied all the design constraints. The T400 needed a connector that was low profile to fit between the LCD and PCB, highly thermally conductive to optimize measurement accuracy, flat-bottomed to thermally mate with the PCB, and have geometry such that it can be used with a pick and place machine and surface mount soldered. On top of those unique requirements we still needed a solid connector with the right insertion force and durability. It also had to fit a fairly wide range of connector thicknesses.

We looked everywhere and could not find a suitable connector. Omega sells a good PCB-mount thermocouple connector, but it was simply too large for the T400. The Keystone 3550 automotive blade fuse clip was nearly perfect. We even used it for prototyping. Unfortunately, the Keystone connectors would deform with some mini thermocouple connectors, so we had to go full custom.

What we get out of this will be worth all the extra work. This connector will be reused in our products and made available for others to use in their custom projects. It is also a great educational resource because as far as we can tell, this is the world’s first and only opensource connector.

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Custom thermocouple connector manufacturing design specification

We do most of our development in public on Github. If you would like to see our entire development conversation, you can view the thermocouple connector issue on Github.

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