The indices from the formulation symbols “abs”, “amb” and “e” Plainly determine the reference place with the respective pressure. They are only hooked up for the formulation letter p, rather than on the unit symbols. In the case of digital pressure gauges, these are occasionally referred to as pressure sensors https://pressuregauge20853.timeblog.net/46468201/the-5-second-trick-for-pressure-gauge