High Flow Positive Bias Relay (M1500A)

The Model 1500 Positive Bias Relay is designed for applications that require an output pressure that is the sum of a controlled input signal plus a fixed bias. This pneumatic relay provides high output flow at an output pressure that represents the input signal pressure plus a preset bias. The output of the relay is the sum of the spring bias, set with the Range Screw, plus a pneumatic input signal. (Po = Ps + K); where Po is output pressure, Ps is signal pressure, and K is the spring constant set by the Range Screw.


  • Control sensitivity of 1" water column
  • Large Supply and Exhaust Valves
  • Soft Supply and Exhaust Valve seats
  • A balanced Supply Valve
  • Aspirator Tube design
  • A separate Control Chamber
  • Unit construction


  • Allows use in precision applications
  • Provides high forward and exhaust flows
  • Minimises air consumption
  • Minimises the effect of any supply pressure variation
  • Compensates downstream pressure droop under flow conditions
  • Isolates the diaphragm from the main flow to eliminate hunting and buzzing
  • Allows service without removal from the line

See PUB103-071 for further information.

High Flow Positive Bias Relay (M1500A)