Can anyone identify this tiny connector? The tape measure is in inches. The connector has threads on the outside and a pin inside. The diameter is about 1/16th of an inch. I think it might be an SMC connector but I am not an expert in this stuff.

This connector is on an accelerometer. I will need to get a custom cable to connect to the accelerometer; the other end will be a BNC connector. Does anyone know what type of cable I would want to use for this? My lab mainly uses BNC cables, and they're all RG58, which is way too big for this tiny accelerometer.

Side view of connector

Front view of connector

  • \$\begingroup\$ Is this the same connector you asked about in another question? electronics.stackexchange.com/questions/81136/… \$\endgroup\$
    – The Photon
    Commented Sep 3, 2013 at 16:32
  • \$\begingroup\$ No, this is a different and smaller connector. This one is on an accelerometer. \$\endgroup\$
    – user28432
    Commented Sep 3, 2013 at 16:38
  • \$\begingroup\$ No, while the pin/socket polarity is correct for SMC, SMC uses a #10-32 thread which is substantially larger than "1/16th of an inch" in diameter. Also, online pictures of SMC connectors show more of "nose" protruding beyond the threaded portion. \$\endgroup\$ Commented Sep 4, 2013 at 1:53
  • 2
    \$\begingroup\$ The documentation mentions the accelerometer comes with a "Coax Cable, 10 ft (3 m), 3-56 plug to 10-32 plug" but I couldn't find any info on what a 3-56 plug is. \$\endgroup\$
    – PeterJ
    Commented Sep 4, 2013 at 2:43
  • \$\begingroup\$ Those are both machine screw sizes, perhaps someone made custom connectors out of them. If your sensor bandwidth is not multiple MHz you might be able to improvise with brass hardware. But 3-56 is a bit uncommon compared to 2-56 and 4-40. Searching for older connectors with that thread might be effective. \$\endgroup\$ Commented Sep 4, 2013 at 5:04

3 Answers 3


I'll add this as a new answer.
Mark & Chris are correct - it is NOT a SSMA connector.
This answer is based on an extension of what they discovered The cable designed for use with the accelerometer is shown here

PCB Piezotronics -
Model: 030A10 Miniature, low-noise, blue coaxial cable, 10-ft, 3-56 plug to 10-32 plug

enter image description here

If you want the "EK" connector only it is here (as Chris advised): EK connector -

Coupling Thread 3-56 female
Size - OD 0.12 in / 3.0 mm
Size - Length 0.29 in / 7.4 mm

enter image description here

With the above information an excessively enthused technician could construct a workable plug

OR ...

PCB Piezotronics contact page:


That appears to be an "RP SSMA" or "Reverse Polarity SSMA" connector

IF you find an SSMA (or other connector of the same size but it is not an RP version as your is, you could make an adequately workable one off by machining down a plug (whose centre will fit your plug) and then ensuring that adequate outer contact is made. Even if this involved bonding (eg soldering) your unit to a cut down plug it would work if done well.

SSMA is a (even more) miniature version of SMA.
RP or reverse polarity is when the plug centre is a male pin rather than a socket and the outer is a male thread, as shown in your picture.

This image from Wikipedia - SMA Connector shows an RP connector (as yours is) but this is an SMA.

enter image description here

Amphenol SSMA with catalog - may not have RP

Southwest Microwave - have SSMA PLUS smaller, still smaller and still still smaller versions.
One MAY match yours. May not have RP.
2.92 mm, 2.40 mm, 1.85 mm versions !!!
1.85mm - 67 GHz !!! - not RP as shown here

Dimension chart below from here

enter image description here



Notionally reverse SSMA images - MAY be of some use - note that many are not RP SSMA.

Future RP SMA - MAY know of SSMA

Aliexpress and similar can be a source of specialist parts - these are not exactly what you want but show that small volume sellers of semi-specialist parts can be found.
Also hgere

RF Globalnet SSMA

Microwave 101 connector page

Smaller ...

Amphenol may save you - or not

Southwest microwave catalog pages

... beyond the catalog.

  • 2
    \$\begingroup\$ With the 3-56 thread specified, it's less than half the size of an SSMA. It may be worth remembering that it is an accelerometer with a bandwidth that likely extends barely into the MHz range (and probably quite a bit less), rather than a microwave system - it's probably a coaxial connector for the same reasons audio cables are, threaded for security, and tiny to keep it very low mass. \$\endgroup\$ Commented Sep 6, 2013 at 2:55

No. This is not an RF/microwave connector, but a special "3-56 coaxial" or "EK" accelerometer/instrumentation connector.

markrages found mention of it at:


I also find it mentioned at:


Which has pictures and specs of units of the same sort you have, though on further reading it appears they are just a distributor and point back to PCB as the manufacturer.

Contacting one or both companies would probably be the best way to track down a source for a cable or connector, which may be part 030A10.


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