So I wasn't real happy with the first Spoke Tension Meter that I printed. It works and it works very well. Provides consistent readings, but it is a bit unwieldy in use. This is a different design that used less parts. I have released all the files necessary to print your own on Thingiverse using a Creative Commons license. The parts list is reduced from the previous design. In my testing it too is very consistent in readings. With a digital dial indicator it would also be much lighter. The Park Tools one in the picture is very heavy and was just leftover from another project.
My printed Spoke Tension Meter
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All the files, including 3D CAD files that can be imported into your favorite CAD application, are included at this link
https://www.thingiverse.com/thing:3209607
Feel free to download, print and or modify it for your needs.