The Brooks Instrument 5866RT combines a pressure controller and a thermal mass flow meter in a single device — it controls upstream or downstream pressure while simultaneously measuring the resulting flow rate. The control loop uses a remote pressure transducer signal (0–5 or 0–10 V from any compatible transducer) as the process variable, with onboard PID electronics driving an integrated control valve. The result is a single instrument that both regulates pressure and reports flow, replacing a separate pressure regulator, flow meter, and transducer in gas delivery systems for thin-film deposition, fuel cell testing, and laboratory research.

How is the PID tuning adjusted in the field?

Rather than requiring software or a PC connection, the 5866RT uses a 10-position DIP switch mounted on top of the controller housing. Switches 1–3 set the command ramp time constant (shorter ramp = faster response, longer ramp = less overshoot). Switches 4–7 set the integration time. Switches 8–10 set the derivative action. All switches on = fastest response across all three parameters; all off = maximum damping. This hardware-based tuning means the controller can be optimized for a specific gas, pressure range, and downstream volume on the bench without connecting a laptop — the technician adjusts the DIP switches, observes the step response, and locks in the settings.

What seal and valve configurations are available?

Elastomer seals (Viton standard, Buna-N, Teflon, or Kalrez options) provide leak integrity to 1 × 10⁻⁹ atm cc/sec He. Metal seals improve this to 1 × 10⁻¹⁰ atm cc/sec He for ultra-high-purity or vacuum applications. The integrated valve is available in normally closed or normally open configurations, or the controller can be ordered without a valve for flow-meter-only operation. An internal jumper (J7) reconfigures the unit from pressure controller to mass flow controller mode — the same hardware serves either function. An electrically activated valve override on Terminal 12 forces the valve fully open or closed regardless of the control setpoint, useful for system purging or emergency shutdown.