Model T5221 Electro-pneumatic I/P, E/P Transducer

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The Fairchild T5221 maintains consistent ouput under pressure shock and vibration conditions. Temperature compensation provides stable operation under environmental changes.


  • Adjustable Positive and Negative Bias permits use with various final control elements.
  • High Output Flow meets requirements for most industrial control applications.
  • Adjustable Gain allows a single device to cover most industrial and process control requirements.

Operating Principles

The Fairchild T5221 Transducer is an electropneumatic device that converts a DC current or voltage input signal to a proportional output pressure. This device is made up of four sections, the Signal Conversion Section, the Pneumatic Section, the Ratio Section, and the Booster Section.

The Signal Conversion Section (PC Board) accepts a DC current or voltage. This signal current is applied to a Coil which creates a magnetic force that moves a Flexure Arm.

The Pneumatic Section operates as a force balance system. A Sapphire Ball floats inside a Nozzle and controls the output pressure by exhausting air supplied through an Orifice. This Sapphire Ball acts as a piston exerting a force which is balanced against the force transferred to the Flexure arm by the Coil. Signal pressure from the Pneumatic Section is routed to the underside of the Signal Diaphragm in the Ratio Section. Signal pressure acting on the Signal Diaphragm transmits a force through the lever to the Control Diaphragm of the booster. The output pressure is a function of signal pressure times the ratio of lever arm lengths on either side of the Pivot.

The Booster Section supplies the unit's output pressure. At set point, the lever Arm force acting on the top of the Control Diaphragm is balanced by the force due to the booster output pressure acting on the underside of the Control Diaphragm.



Output Range
Minimum: 10” (25.4 cm) Water Column to 50” (127 cm) Water Column
Maximum: 0-150 psig, [0-10 BAR], (0-1000 kPa)
Supply Pressure
Transducer: 20 + 2 psig, [1.5 + 0.15 BAR], (150 + 15 Kpa)
Ratio Relay1: 250 psig, [17 BAR], (1700 kPa)
Air Consumption
0.36 (0.6 m³/HR) Maximum
Output Capacity (SCFM)
40 (68 m³/HR) Maximum with 100 psig, [7 BAR], (700 kPa) Booster supply
Exhaust Capacity (SCFM)
5.5 (9.4 m³/HR) downstream pressure @ 5 psig, [.35 BAR], (35 kPa) above 20 psig, [1.5 BAR], (150 kPa) setpoint.
Supply Pressure Effect
Transducer: 1 % of Span for a + 2 psig, [.15 BAR], (15 kPa) change.
Ratio Relay: Less than 0.1 psig, [.007 BAR], (.7 kPa) for 100 psig, [7 BAR], (700 kPa) change.
Terminal Based Linearity
+ 0.50 % Full Scale
Independent Linearity
+ 0.25 % Full Scale
RFI/EMI Effect
Less than 0.5% of Span @ 30 v/m class 3 Band ABC (20-1000 mHz) per SAMA PMC 33.1 1978 and less than 0.5% of Span @ 10 v/m level 3, 27-500 mHz Band per IEC Standard 801-3 1984. EMC Directive 89/336/EEC European Norms EN 50081-2 and EN 50082-2.
Impedence / Input Signal

Range OHMS
1-5 mA 2000
4-20 mA 1202
10-50 mA 502
1-5 VDC 375
1-9 VDC 2550

Ambient Temperature
-40°F to + 150°F, (-40°C to 65.5°C)
Materials of Construction
Body and Housing: Aluminum
Ball and Orifice: Sapphire
Nozzle: Stainless Steel

1 Supply Pressure must be no less than 10 psig, [0.7 BAR], (70 kPa) above max. booster output.
2Add 332 OHMS for CSA units.

Catalogue PDF: application/pdf
Operational PDF: application/pdf
Located in: Transducers

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