Amphenol / SV Microwave SF2921-61506-1S SMA coaxial connector: behavior under vibration

4 Mar 2023

Amphenol / SV Microwave SF2921-61506-1S SMA coaxial connector: behavior under vibration

In this post I test the Amphenol / SV Microwave SF2921-61506-1S SMA coaxial connector's DC resistance behavior when vibrating. How well does the spring contact stays connected to the PCB?

I want to check if, under vibration, the middle contact keeps in touch with the copper pad it's pushing against. I've mounted a connector on shabaz 's test PCB, and soldered test leads to signal and ground. I then made a shortcut in the adapter using aluminium foil and kept that locked in place by mounting some devices on it. I used a sub 1-GHz antenna (photo in the mail header) and a little SMA gender-converter. Both tests are interesting because they have a different mass, and they behave differently at resonance frequencies. In both cases, I measured approximately 155 mΩ at rest. Fiddling with the setup doesn't change that.

I mounted the PCB on a the shaker from the Vibration Measurement with the MCC 172 roadtest.

I vibrated the setup between 20 and 150 Hz.

The vibrations are visible on the resistance graph, +- 0.5 mΩ. That is nothing, and very likely interference picked up in the measurement setup. If I switch my meter to mV, it shows the vibrations too.

For short periods, I drove the shaker to its maximum, and the connection never interrupted. In this vibration test, I could not break the contact. The connector survived all conditions. I also did a thump test: hit the PCB on a ceramic plate. That didn't break the contact either.

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Jan Cumps over 3 years ago in reply to javagoza

javagoza , this is the proposed setup for it:

4 wire resistance measurement over the shorted connector, and a K-type temperature probe fixed to the ground pour.
Temperature will not be perfect, I don't currently have a cold junction reference. I took the room temperature as reference.

I'm using a switch card. The fact that both the probe and the resistance measurement wires touch the ground, will not influence measurements.

I don't have a programmable heater, but I can put the test board over a heater and measure temp and resistance while the whole contraption is warming up ...
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Jan Cumps over 3 years ago in reply to javagoza

I could try and write a LabVIEW process, and post that design to the new LabVIEW area /products/devtools/ni-labview/#pifragment-17004=4
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shabaz over 3 years ago in reply to shabaz

Example mil connector for battery packs. This was quite a neat design, the metal contacts made a springy contact against the faces. However, there are also holes in the two contacts, which are not ordinarily used, but are brilliant in the field (I guess), since they are standard banana-plug sized holes. So at a pinch, any power supply can be used to charge the battery pack up (this is Nickel-Cadmium).

(Image source: ebay).
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javagoza over 3 years ago

Is there also a temperature variation in the connector or is it difficult to make this measurement?
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shabaz over 3 years ago

Hi Jan,

Excellent work! And very nice set-up. Love the charts from your app (that MCC 172 data acquisition product is awesome of course) and the DMM6500 chart. Thinking back, I recall even some military equipment uses spring contacts, e.g. on batteries, and so it's good to see you've shown how it can be tested!
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