April 5, 2021 Test Equipment, Extremophile

Triaxial Holocaust

The massacre of triaxial stuff

Triaxial Holocaust

I currently own tree instruments with triaxial BNC ports and no cables or connectors. A 601 electrometer, a 617 electrometer and a 224 current source. All with the old 2 lug triaxial connector.

I need at least 2 triaxial cables with BNC connectors. Something like the POMONA 4725.


The question is how not to spend a fortune. Each cable costs about US$115.

Another disadvantage is that the alligator clips are too big and cannot easily pass through a cable gland. This is important since most low level measurements take place in Faraday cages.

Also the 2-lug BNC connector means that the cable will not be usable with any newer devices with 3-lug connectors I may acquire in the future.

To build a cable from scratch is not much cheaper either. The triaxial plug with the lowest price on Digi-Key is the 3-lug PL75-47 and costs US$23.45. The 2-lug version PL74-47 costs 10 dollars more. At the time of writing the classic triaxial cable BELDEN 9222 cannot be found at a reasonable price in small quantities although at 30m (100 ft) it costs about US$3 per meter.

In the end I decided to file down a lug from each instrument and go for a 3-lug cable. I ordered an assembled 3-lug triaxial cable (BU-P5223-60 US$109) and cut it in half to make two cables.

The alligator clips are small enough to pass through an M16 cable gland

List of materials

Description Part Number Supplier
Cable BU-P5223-60 Digi-Key
Alligator clip CTM-30C Digi-Key
Cable gland LAPP 53112010 Reichelt
EMC nut LAPP 54110840 Reichelt

Photos from the massacre