Hi Peter, Could it be an Amphenol 165 series connector (like the 165-12)? Look at the bottom of this catalog page http://www.alliedelec.com/catalog/pf.aspx?FN=3D160.pdf also some images here: http://www.dfwairparts.com/Amphenol.html These are used on Tektronix current probes like the venerable A6303. The A6303 is a DC to 15MHz probe which combines a current transformer with a hall sensor and current feedback coil. The current in the feedback coil is adjusted to keep the low frequency flux in the core at near zero. The signal to drive the feedback coil forms the low freq portion of the output signal. The remainder of what comes out of the current transformer is the high frequency signal. These two signals get combined (and the feedback coil current is generated) in the probe amplifier, which is a separate module (like the AM503 or AM503A). Sean On Tue, Jul 27, 2010 at 12:16 AM, Peter Loron wro= te: > I have several clamp-on current probes that I'm trying to figure out. The= y have a screw-on connector that looks a bit like an XLR connector. There a= re 4 pins arranged in an arc across maybe 1/3 of the circumference of the c= onnector. > > I'm familiar with the 2-pin probes or plain current sense transformers, b= ut I'm not sure what to make of this one. > > These probes are SPX brand, but I have been unable to track down any furt= her information about them. Presumably they go into some kind of automotive= diagnostic tool. > > Any pointers from the hive mind? > > Thanks! > > -Pete > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .