CAT scales are just one of the options. Nearly every large truck stop will have a scale. CAT has very strict standards and a legal department that will defend the accuracy of a weigh on their scales. This is valuable for a commercial truck because of the problems caused if state scales find a truck over-weight. CAT scales are usually the most expensive - because of marketing and value-added services.
Since we RV-ers are typically well below the 20,000 lb single, or 34,000 lb tandem, or 80,000 lb gross weight limit the extra benefit of using CAT scales is typically of little value. So check around. Another chain of scales in Interstate. Then there are the other places with scales. I use the local Farmers Association store. $1.25 for a pickup and trailer. Or look for trucking companies, grain elevators, quarries, scrap metal yards, city recycling centers, landfills, landfill transfer stations, or anyplace that does commerce based around the weight of material in a truck.
As others have said, in some states the state scales can be used even when the LOE isn't on duty. Other states block the scales, or even put up cones or barrels to block the exit ramp.
Cedarhill, the reason for concern over not being in the TV during the weigh is where would you add the weight? Front only? Rear only? 50% split? 35% front and 65% rear? :B