4122 belt tension-o-meter alternative?

[ihatecars]

I'm looking at replacing the auxiliary belt on my 1996 1.8 8v (no air con)130k miles Xantia. The exisiting belt works fine but I notice it has lots of cracks and gives me impression he intends to let go at some unsuspecting moment.

So for replacement, this look to be the correct part:-
http://www.eurocarparts.com/ecp/c/Citro ... 21e&000108

Anyway the reasons for my posting is regarding tension. The Haynes manual suggests the use of Citroen SEEM 4122 electronic tension guage/meter which looks like a " force over distance to measure displacement" device. So I wonder if you clever people have an alternative.
To my mind, dangle a known weight between two known points and measure deflection, that sounds complicated and I guess what the 4122 does. But what is the common solution?

Thanks

[lexi]

Tension it to just less than 90 deg twist. I do the cam belt to about 45deg twist. Both at their longest runs on the pulleys. Never any probs.