Thanks for the reply. The client wants to compare the efficiency of performance of various pressure cookers, particularly if solar powered, as panels and batteries cost quite a lot, for use in very offgrid areas. So it will be a test on 10-20 different cookers and some destruction is fine, but best avoided if at all possible.

Took all day to find, but this looks like it would do the job. Any other ideas welcome.
https://www.madgetech.com/products/pr140/