However, what exactly is a diaphragm-sealed pressure-indicating transmitter?
A the pressure of gases or liquids in a process and transmits an electronic signal to a control system based on that measurement. Between the process fluid and the sensing element, the diaphragm seal serves as a barrier to keep it safe from corrosive or viscous fluids as well as high-temperature or high-pressure situations.

The diaphragm-sealed pressure indication transmitter

a diaphragm-sealed pressure indicating transmitter