Why autoclave pressure gauge is 1.2 practically, but has a different amount in the saturated steam tables?

Why autoclave pressure gauge at 121°C, show 1.2 bar but Scientific resources have written 15 psi (or 1.03 bar)???

OK. No problem when transfer bar to psi equal result = 1.2 bar = 17.9 psi almost same result

Yes, maybe not important but temperature and pressure are interdependent, why the amount of the theory is 1 bar but practical amount is 1.2 bar ???

Finally, I discovered the solution:
The gauge pressure required will be higher than the pressure shown in the saturated steam table due to elevation above sea level.

please provide the reference for the same. as it is very useful.


  1. Steam Sterilization Principles by Marcel Dion
  2. Autoclaves by Frank Weithöner