How do I avoid a burnt underlayer with pressure cookers? I use my pressure cooker a fair bit but sometimes I struggle in translating a regular recipe to it and I get a charcoaled underlayer at the bottom of the pressure cooker.  Some of the time the rest is still edible, sometimes it has to be thrown away.

For example, with a split pea soup recipe I ended with some extremely burnt bottom layer which gave a nasty chemical smell that took a while to clear from the apartment.  Obviously the whole thing had to be thrown out.

Not all recipes will necessarily turn out well in a pressure cooker, I get that, but at least I would like to find ways to minimize this particular problem.

I guess I should watch cooking duration and also turn down the heat once the pressure's up.  But ideally I would like something that kept the ingredients from contacting the bottom of the pan and allow only water to circulate there.  Does something like steam wok bottoms exist for pressure cookers?
When we use a pressure cooker, we do so with separate pans inside the cooker - flat round tins, in our case - that can be kept off the bottom by adding something underneath.  Or stack up cook several things at the same time, if the size allows.

I recall seeing these largish round metal rings like an inch high that I think were for that, or (inverted) small steel plate or bowl.  Since there's no (or little) direct contact the bottom doesn't overcook. I imagine some kind of rack or other insert would also work.