I own a couple of very cool and nice looking vintage analog panel meters made by a Czech company called Metra.
The company has existed for a long time and the meters I have are from an era when the company made a wide range of various types of meters. Most common are ammeters and voltmeters with various scales, but to my knowledge the company also made sound level meters, temperature (and maybe humidity?) meters and other meters.
There is a particular type of these meters which I am very fond of the look of:
I think these are from a product line called Metra DHR5. I was able to find a source online which suggests DHR3 and DHR8 also existed and the difference was in the dimensions of the mounting radius (the cylindrical body of the meter) but all have associated face plate dimensions which should be 44 mm for DHR3, 70 mm for DHR5 and 111 mm for DHR8.
http://www.ebastlirna.cz/modules.php?name=Forums&file=viewtopic&t=71592
I'll try to replace this photo with a better one when I feel like setting up a better environment to shoot these in.
My goal in this repository is to model and print an enclosure these are in and then figure out how far I want to take this to see if I could replace the analog guts with digital circuitry.
I don't want to recreate these meters and keep them analog, I don't like these because I am crazy about analog meters, I like them for the look, so I think using an AliExpress sensor circuit in combination with an Arduino or a Raspi will be a better choice for me.
An open question is how to move the indicator needle. I might remake the coil that's inside which moves it but drive it digitally to get the same smooth movement or I might try approximating it using a servo with a gyro attached to get the nice and fluid behavior these have.
As a side note, look at the Metra website to see what kind of meters are still sold today:
https://www.metra.cz/en/products/digital-panel-and-switchboard-instruments/
Taste is absolutely a subjective thing, but I cannot help but feel like these don't hold a candle to the sold the vintage ones have.
This repository documents the process, which is currently ongoing. I will attempt to keep this readme up to date.
The square face enclosure is 70 by 70 mm and 14 mm deep. The radius on the corner is 5 mm according to my eyeballing with the calipers. I should try and scan these using a scanner to get the exact dimensions of the radii in case they are more precise.
There are two other parts of the meter: the body (the backplate of the face part and the cylindrical shape) and the cap (which sits at the end of the cylindrical part of the body).
The square of the body is 68 by 68 mm which means the thickness of the plastic of the face plate is 1 mm (70 - 68 / 2 for both side = 2 / 2 = 1). This seems about right double-checking with the caliper again.
The back plate is thicker at 4 mm thickness. Its corner radius is approximately 4 mm but I should double-check with a scanner the same way I need to double check the front plate.
It has a slot in it and the cylindrical shape is not concentric with the square of the back plate.
I need to measure these details as well as the cap.
Also, the rounded corners on the face plate are round on the dimension of the surface of the face plate. When it goes 3D depth-wise, the corner on that square edge is less that 5 mm. I need to measure that, too.
Shoot the nicer ones I have and shoot them with a real camera and in a better light setting.
The dimensions of these flat areas are known using the caliper so I can find the corner radii using relative measurements on the scan.
This will cut down on the prose when it comes to the current text.
I have described the external dimensions but I might go as far as to recreate the internal niches and stuff, too. Although I will most likely end up with different terminals on the meters so I am not yet sure if I will follow through with it. It might not make sense to do this.
I will very likely need to find a way to score and cut the glass as I doubt I will be able to find off-the-shelf pane with the right dimensions. I've never done this so I will need to learn how to do it, first.
I will most likely just print the scale and transfer it or glue it to a sheet of aluminum. However there is a crazy idea to try which would be to try to find an e-ink screen of the right dimensions (or one I could cut or fold) and using it for the screen. This would enable one hardware type of the meter to exist and whatever it shows and measures could be defined by a hot-swappable sensor circuit board and the firmware.
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