As I wrote, test where you suspect you may have damp.
You get condensation where moist warm air comes into contact with a cool surface or air flow. Because the ability of air to hold moisture increases with temperature, conversely as you cool moist air any excess moisture it cannot now hold is condensed out.
Some condensation is almost inevitable in a caravan that's being used. Anything that oxidises fuel (a flame, All living things including teenagers) produce higher levels of humidity. I estimate that every adult exhales about 250mL of water vapour every day, so 4 people in a caravan overnight are likely to put about 500ml of water in to the air. As this is warmer air, when it finds a cool corner or window it gives it up as condensation.
Gas when it burns for every gram of gas used, the chemical reaction in the flame produces about the same weight of water vapour, so the cooker and oven in caravans can be a major source of water vapour.
The presence of condensation is not a unique indicator of a damp problem, though excessive condensation could be a warning sign.
If you used a damp meter in an area where condensation was present, it would likely give a false 'Damp' reading on the meter.
The best solution to condensation is to maintain good ventilation. A leak free well ventilated caravan put into storage will loose any occupationally derived humidity after a few days. Condensation may still appear from time to time, usually on cold sunny days, where the sun will warm one side but the other side is is cold shadow. Generally nothing to be worried about.
One of the other important things about a damp problem is the apparent location of the wet patch is measures may not relate directly to the location of the source of the problem, and the measured or visible area of damp is likely to be smaller than the affected area behind the wall. It rather like the ice berg, where the visible bit belies the large part under the surface.