The pulse pressure is taken from a suitable spot on the machine to be sealed and is conveyed below the piston of the pressure transmitter. The buffer fluid above the piston is then subjected to a pressure, whose level is conditional on the transmission ratio and the static friction of the sealing elements for the piston and piston rod.

p_s = Buffer pressure

p_i = Pulse pressure

i = Transmission ratio

i =
i = =

Pressure transmitters are used when

• there is insufficient external pressure available and/or
• the buffer medium must not be pressurized with compressed gas and/or
• the pressure to be sealed fluctuates greatly,
• it is not possible to use a thermosiphon vessel for storing and cooling buffer fluids.
  

Operating principle of the pressure transmitter
ps = pi · i.