There are 3 kinds of scales
Bridge scales (These are raised above ground. Most CAT scales are like this
Flat scales (Level with the ground beside them, This is what you need
And portable scales (Weighmasters carry them so do the folks from RV Safety dot com (you will need to play with that a bit or Aweigh we go.
Now in the first too types there are single scales and segmented sub types.
IF you choose to make an appointment with Aweigh we go via the RV safety web site,,, They will find a spot, take you to it and use their scales. they do a bunch of research and only charge a modest fee, I think I paid 40 bucks, well worth it in my opionion but if you are willing to do the research a flat scale at a facility is usually cheaper
Bridge scales CAN NOT BE USED, most CAT scales are bridge type (Above ground)
How to weigh on a segmente4d scale
Park so each axle is on a segment, Get weight #1
Now drive around and park so one SIDE is on solid ground and the other side is on the scale.. Again one sebment per wheel (not tire, but wheel)
For axel weights.. The first pass is it
For side to side (Wheel weights) teh second pass is the side you weighed
The other side is 1st-2nd pass
and it is that easy
IE: if Axle weighs 1600 pounds and the 2nd pass that side is 850 pounds the other end of that axle is clearly the "Missing" 750 pounds.