Controlair Type Transducer · 500X series

500X Electro Pneumatic Converter

The 500X converter is the voltage-input member of the EAA-500 family. It sits between a control room that speaks in volts and a control valve that only understands air, and turns the one into the other at a fixed proportion. Eight E/P part numbers are catalogued, from 3-15 psi at 615 ohms to 3-120 psi at 805 ohms.

Specifications
Use guide
FAQ

Overview

What This Model Is

A pneumatic control valve acts on a pneumatic signal and never touches the electrical signal used in industrial control. The field therefore needs a conversion instrument that takes the electrical signal from the control room and turns it into the gas signal the valve can recognise. That instrument is mounted on the control valve itself: it receives the electrical signal, converts it to a standard pneumatic signal, and delivers that signal into the valve as the pneumatic energy the valve operates on. The 500X converter does that job from a voltage input.

Operating principle

How It Works

Conversion is electromagnetic. The voltage signal is turned into a physical displacement of a mechanical part, which is the baffle in the nozzle and baffle mechanism. One side of the baffle disc carries a thin metal coil structure; current through that coil in the field of a permanent magnet moves the disc against the nozzle, the nozzle back pressure changes, and the pneumatic power amplifier turns that change into a usable output.

Photographs

500X Electro Pneumatic Converter On Our Benches

Studio and workshop photographs of the units as built, not renderings.

Key benefits

What You Get From This Model

Takes the voltage signal directly

0-5 VDC, 1-9 VDC and 0-10 VDC units are catalogued, so a voltage loop does not need a signal converter in front of the transducer.

Impedance is published

Each part number carries its coil impedance, from 500 ohms to 985 ohms, so loop loading can be checked on paper before the order goes out.

Same body as the current version

The converter and the transducer share the 500X body, ports and adjustment screws, so a site stocking both keeps one set of fittings and brackets.

Drives the actuator without a booster

The integral amplifier produces enough flow to move a control valve actuator on its own.

Application scenarios

Where It Is Used

DCS and PLC voltage outputs driving pneumatic control valves
Retrofit of an electronic controller onto an older pneumatic plant
Laboratory and pilot plant rigs running on 0-10 V signalling
Pneumatic positioners fed from a voltage source

Who it is for

Who Orders It

Plants that standardised on voltage rather than current signalling
System integrators bridging an electronic controller to pneumatic final elements
Maintenance teams replacing a failed E/P unit of the same pattern
OEM skid builders specifying a voltage-input conversion stage

Problems it solves

What This Model Fixes

The control room signal and the valve do not speak the same language

The converter is the translation stage, mounted at the valve so the electrical run ends where the pneumatic run begins.

A voltage loop has been forced through a current converter

Ordering the E/P part number removes the extra signal conditioner and the failure point that comes with it.

Loop loading is unknown

Published impedance per part number lets the loop be checked before commissioning instead of during it.

Technical features

Features And Specifications

Every figure below is transcribed from the datasheet EAA publishes for this series. Anything not published is not listed.

Voltage input, linearly proportional pneumatic output
Eight catalogued E/P part numbers
Published coil impedance for every range
Nozzle and baffle section with pneumatic power amplification
External zero and span screws on the front face
1/4 NPT and 1/2 NPT porting

Type 500X I/P transducers — EAA 500X data sheet
Part number	Input	Output psi	Output BAR	Impedance
500-AA	4-20 mA	3-9	0.2-0.6	90 Ohms
500-AB	4-20 mA	9-15	0.6-1.0	90 Ohms
500-AC	4-20 mA	3-15	0.2-1.0	180 Ohms
500-AD	4-20 mA	3-27	0.2-1.8	220 Ohms
500-AE	4-20 mA	6-30	0.4-2.0	220 Ohms
500-AF	4-20 mA	1-17	0.1-1.2	250 Ohms
500-BC	10-50 mA	3-15	0.2-1.0	70 Ohms
500-BD	10-50 mA	3-27	0.2-1.8	85 Ohms
500-BE	10-50 mA	6-30	0.4-2.0	85 Ohms
500-AG	4-20 mA	2-60*	0.14-4.1	225 Ohms
500-AH	4-20 mA	3-120*	0.2-8.2	260 Ohms
500-BF	0-60 mA	2-120*	0.15-8.2	220 Ohms

Type 500X E/P transducers — EAA 500X data sheet
Part number	Input	Output psi	Output BAR	Impedance
500-CC	0-5 VDC	3-15	0.2-1.0	615 Ohms
500-CD	0-5 VDC	3-27	0.2-1.8	530 Ohms
500-CE	0-5 VDC	6-30	0.4-2.0	530 Ohms
500-DC	1-9 VDC	3-15	0.2-1.0	985 Ohms
500-DD	1-9 VDC	3-27	0.2-1.8	840 Ohms
500-DE	1-9 VDC	6-30	0.4-2.0	840 Ohms
500-CF	0-5 VDC	2-60*	0.14-4.1	500 Ohms
500-EH	0-10 VDC	3-120*	0.2-8.2	805 Ohms

* Output shown is as calibrated at the factory. The large span adjustment range allows recalibration to 3-35 psig (0.2-2.4 BAR) on the 2-60 psig unit and to 3-145 psig (0.2-10 BAR) on the 2-120 psig unit.

500X Electro Pneumatic Converter specification sheet — Specification sheet published for the 500X, as served by EAA Electric.

Use guide

Selecting Installing And Calibrating

Confirm the source can drive the coilCheck the controller output against the impedance printed on the part number, between 500 and 985 ohms depending on range.
Mount at the valveThe converter belongs on the field valve, so the electrical cable run ends there and the air run is short.
Pretreat the airA filter and pressure reducing device at the inlet keeps the instrument air constant and free of impurities.
Calibrate against the valveJoint calibration with the connected valve is the normal practice and takes less work than calibrating the instrument in isolation.

Comparison

How It Compares With The Alternatives

The converter differs from the transducer only in the input stage: volts instead of milliamps. Everything downstream, the nozzle and baffle, the amplifier, the ports and the adjustment screws, is the same. Against a valve positioner it is still an open-loop device, so it produces a signal pressure rather than forcing a stem position.

Comparison within the EAA range
Model	Distinguishing specification	Best suited to
500X Electro Pneumatic Converter	0-5 V, 1-9 V and 0-10 V input	Voltage signalling
500X Electro Pneumatic Transducer	4-20 mA, 10-50 mA and 0-60 mA input	Current signalling
EPC1000 Electro Pneumatic Transducer	Current input, direct acting, coded ordering	High-power output into large-bore valves