[quoteHang known weight from a cable and measure the tension. [/quote]

I am going to comment before somebody starts tying some old wire to a tree limb and hanging their dumbbells from the other end to calibrate their Loos gauge.

There is a procedure for calibrating deflection gauges and just hanging weights will not work.

At a minimum both ends of the test wire must be constrained like they are on what you are measuring and there are minimum wire lenghts.

I would not calibrate a Loos gauge unless I was calibrating it against the actual wire in the actual configuration. What Loos gauges actually measure deflection. How this relates to tension depends on a lot of things (alloy, hardness, style, # of strands, age etc). There is a lot of conservatism built into those charts Loos provides and you could get into a lot of trouble if your test was optimistic.

If you buy a calibrated load cell, stick it in line with your rigging, and then load it up and see what the Loos gauge shows, GREAT. However just hanging a weight from the end of a wire, might not work so well.