Electronics > Metrology

Pomona 3770 Binding Post CAD

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leighcorrigall:
Pomona offers a relatively inexpensive entry-level binding post https://www.pomonaelectronics.com/file/17329/download?token=JnxIsd1L that uses brittle polycarbonate as an insulator and a tellurium-copper conductor. They provide basic assembly components like nickel-plated steel parts for the rear fasteners.

Some EEVBlog members may find it beneficial to have a CAD model of such a product. Others will have to forgive me if they do not appreciate this product being mentioned in the metrology section. I personally would never use them, but I figured I would lend a favour to those that use them for their designs.

Attached is the reverse-engineered CAD assembly. Use 7-Zip https://www.7-zip.org/ to extract the STP file.

Please use it at your own risk. I do not know what the front thread is exactly. It seems to be a metric thread but is not standard. If anyone does encounter significant discrepancies, please let me know so that a revision can be made.

A special thanks to TiN for giving away his broken collection.  ;D

Enjoy?

eplpwr:

--- Quote from: leighcorrigall on October 15, 2021, 03:00:05 am ---Pomona offers a relatively inexpensive entry-level binding post https://www.pomonaelectronics.com/file/17329/download?token=JnxIsd1L that uses brittle polycarbonate as an insulator and a tellurium-copper conductor. They provide basic assembly components like nickel-plated steel parts for the rear fasteners.

Some EEVBlog members may find it beneficial to have a CAD model of such a product. Others will have to forgive me if they do not appreciate this product being mentioned in the metrology section. I personally would never use them, but I figured I would lend a favour to those that use them for their designs.

--- End quote ---

Are the 3770's really that bad? From a metrology POV? Yes, the steel nut and washer only do for fastening, but I solder the wires at the rear end. Polycarbonate bad? What about the electrical conductivity of other plastics used by other mfgs? If I am to have a metrology problem with the 3770's, please tell me why. "Brittle"? My motorics are not as in my younger years, but I have still not cracked a 3770 when tightening. (100+ of them.)

Thanks for the drawing, anyway.

leighcorrigall:
This topic was not intended to start a debate about Pomona 3770 quality. I care little what people want to buy for themselves.


--- Quote from: eplpwr on October 16, 2021, 06:17:21 pm ---
Are the 3770's really that bad? From a metrology POV? Yes...


--- End quote ---

Personally, if I am going to spend 100's of dollars on a metrology-grade designs I am not going to have them compromised by these binding posts.


--- Quote from: eplpwr on October 16, 2021, 06:17:21 pm ---
"Brittle"? ... I have still not cracked a 3770 when tightening.


--- End quote ---

I have about 5 of them from TiN and they are brittle. The ones that are not pictured are in very poor condition. They were purchased from DigiKey in the last couple of years and removed from the intended design after signs of cracking appeared. See attached photos.

The older variations of these binding posts are of good quality. See attached. These were taken from a few Keithley 616 units. There are slight differences between these old posts and the new binding posts sold by Pomona. For example, they do not crack, they have high-quality copper nuts, and they have a coarser thread for the post cap.

You are welcome.

dietert1:
I am using about 20 of the Pomona 3770 binding posts (from Digikey and Mouser). I have to crack one yet. The only suspicion i have is the knob may be brass. As far as i remember there is something fishy.

Nice thing about them is you can combine them with Pomona 3750 that look the same but are all brass and available in other  colors. So i use those for guard terminals.

Regards, Dieter

TERRA Operative:
I've used a handful of both types in the same way as dietert1 and so far so good.

I wonder if the cracking is due to some sort of environmental factor?

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