500ACD Electro Pneumatic Transducer
The EAA-500ACD is an electro pneumatic transducer for control applications.
What This Model Does
The EAA-500ACD is an electro pneumatic transducer for control applications. It converts a DC 4 to 20 mA input signal into a linearly proportional pneumatic output pressure of 0.02 to 0.1 MPa. It operates on a force balance principle, using a coil and permanent magnet to displace a baffle near a nozzle, creating back pressure that drives the output. The feedback bellows and lever system maintain balance so the output pressure matches the input signal. It is a form fit and function replacement for the Controlair 500ACD model already used in many process control systems.
| Model | EAA-500ACD |
|---|---|
| Type | Electro pneumatic transducer |
| Input signal | DC 4 to 20 mA |
| Output pressure | 0.02 to 0.1 MPa |
| Operation | Force balance |
| Adjustment | External zero and span |
| Action | Single acting |
| Housing colour | Black, blue, yellow or painted to order |
| Warranty | 18 months |
Why Buyers Specify This Model
- Converts DC 4 to 20 mA signals directly to pneumatic output without needing a separate valve positioner
- Maintains linear output pressure across the full input range for consistent control
- Uses force balance operation to reduce drift and improve repeatability
- Provides stable output pressure even under varying supply air conditions
- Designed for reliable performance in continuous process control environments
- Supports zero and span adjustment for field calibration
- Drop-in replacement for Controlair 500ACD, so no actuator or piping changes are needed
Problems It Solves
- Original brand transducer is on long lead time or no longer available for that model
- Transducer output drifts over time due to internal wear or dirty air
- Control loop instability caused by non-linear output pressure response
- Need to replace a transducer without modifying the actuator mounting or piping
- Lack of spare transducers in stock for critical process valves
Application Scenarios
- Replacing a failed Controlair 500ACD transducer on a control valve without changing the actuator or piping
- New skid build where the valve supplier ships the actuator without a transducer
- Plant upgrade where the original transducer is discontinued but the system still uses 4 to 20 mA signals
- EPC project requiring multiple transducers with consistent performance and quick delivery
- Maintenance team replacing a transducer with a known failure mode like pressure drift or signal lag
Who It Is For
- Plant instrument technicians replacing worn or failed transducers on control valves
- EPC contractors buying transducers in bulk for plant construction projects
- Valve and actuator assemblers who fit transducers before shipment
- Distributors stocking Controlair 500ACD spares for local process plants
- OEMs who need the same transducer supplied under their own brand and colour
Technical Features
- Converts DC 4 to 20 mA input to pneumatic output pressure of 0.02 to 0.1 MPa
- Force balance operation with internal permanent magnet and coil
- Baffle and nozzle mechanism for pressure generation
- Feedback bellows and lever system to maintain signal-pressure balance
- External zero and span adjustment for field calibration
- Single acting output for pneumatic control valves
- Clean dry instrument air supply required for stable operation
Materials and Construction
- Cast aluminium alloy housing with painted finish
- Stainless steel feedback bellows and lever components
- Full material and finish breakdown is given in the datasheet PDF
Dimensions and Connection Detail
Reference image published with this model on the original catalogue. Confirm critical dimensions against the datasheet before machining a bracket.
Manufacturing and Quality Control
Every unit is calibrated and stroke tested before it is packed. We can film or photograph your units in the sample room or warehouse before they ship.
Manufacturing Steps
Housing casting and machining
Coil and torque motor assembly
Nozzle flapper and feedback bellows integration
Zero and span calibration on an air bench
Signal sweep test across the 4 to 20 mA range
Painting in the customer colour and logo marking for OEM orders
Packing in stock or customised cartons
Quality Control
- Every unit is calibrated and pressure tested before packing
- Photos or video of the actual units can be taken in the sample room or warehouse before shipment
- Faulty units inside the 18 month warranty are replaced on photo or video evidence, not repaired
- Replacements normally ship with the customer next order, or immediately when the plant is down
Customisation Options
- Customer logo and nameplate marking
- Housing painted in the customer colour
- Newly designed shape modules developed to customer drawings
- Customised carton and inner packaging
- Supplied assembled with a limit switch box or position transmitter module
How It Compares With the Alternatives
| Controlair 550X transducer | The 500ACD is a lower cost option with the same input and output range; the 550X has higher precision and digital diagnostics |
|---|---|
| I/P transducer with external feedback | The 500ACD has internal feedback for better stability; external feedback requires more setup and maintenance |
| Intelligent digital transducer | A digital transducer adds HART or fieldbus; the 500ACD is the lower cost choice where basic signal conversion is all that is needed |
| Pneumatic positioner without I/P conversion | The 500ACD converts electrical signal to air pressure directly; a positioner requires a separate I/P converter to drive it |
Fitting and Setting Up This Model
General field procedure. Always follow the datasheet for the exact calibration sequence and any hazardous area requirements.
Mount the transducer on the actuator bracket using the standard Controlair pattern
Connect clean dry instrument air to the supply port and the actuator to the output port
Wire the DC 4 to 20 mA signal observing polarity
Set the zero at 4 mA by adjusting the zero screw until output pressure is 0.02 MPa
Set the span at 20 mA by adjusting the span screw until output pressure is 0.1 MPa
Repeat zero and span adjustments until both points hold under load
Check the air filter regulator regularly; dirty air is the most common cause of drift
500ACD Electro Pneumatic Transducer FAQ
Will this fit the bracket already on my actuator?
If the actuator carries a Controlair 500ACD today, yes. Send a photo of the existing bracket over WhatsApp and we will confirm before you order.
What is the lead time?
Regular quantities normally ship in 2 to 3 days from stock. Large project quantities take 7 to 10 days.
Can I get it in our own colour with our logo?
Yes. The housing is painted to your colour and the nameplate carries your logo. Black, blue and yellow are already tooled; other colours are painted to order.
What is the difference between the 500ACD and 550X models?
The 500ACD is a standard force balance transducer with basic calibration. The 550X has higher precision and digital diagnostics, but the 500ACD is sufficient for most standard control applications.
What happens if a unit fails on site?
The warranty is 18 months. Send photos or a short video, and we ship a replacement unit rather than asking you to return it for repair. It normally travels with your next order, or on its own if the plant is down.
Do you supply the limit switch box and transmitter as one assembly?
Yes. The transducer can be supplied already assembled with a 210, 410A or 410B limit switch box, or with an internal or external position transmitter module.
Can I see the actual units before they ship?
Yes. Ask on WhatsApp and we will photograph or film the units in the sample room or warehouse before packing.
Applications Cases and Guides
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