TD7800 Electro Pneumatic Transducer
The TD7800 is an electro pneumatic transducer that converts a DC 4 to 20 mA signal into a proportional pneumatic output...
What This Model Does
The TD7800 is an electro pneumatic transducer that converts a DC 4 to 20 mA signal into a proportional pneumatic output pressure. It is a form fit and function replacement for the Fairchild T7800 series transducer used on control valves and actuator systems. It operates with internal electronic feedback and a solid state piezoelectric actuator to maintain stable output under vibration or changing orientation. The unit is rated IP65 and NEMA 4X for indoor and outdoor use, and supports split range and field reversible operation.
| Model | TD7800 |
|---|---|
| Type | Electro pneumatic transducer (I/P, E/P) |
| Output pressure | Proportional to input signal |
| Reversibility | Field reversible output |
| Enclosure rating | IP65, NEMA 4X, Type 4 |
| Protection | RFI/EMI |
| Mounting | Multiple configurations available |
| Damping | Adjustable |
| Split range | Supported |
| Warranty | 18 months |
Why Buyers Specify This Model
- Converts DC 4 to 20 mA signal directly to proportional pneumatic output without needing a separate positioner
- Internal electronic feedback maintains output accuracy regardless of vibration or mounting position
- Field reversible mode allows output to be inversely proportional to input signal
- Split range operation enables one signal source to control two or more functions
- Compact size fits in tight or confined spaces
- RFI/EMI protection ensures stable operation in electrically noisy environments
- IP65 and NEMA 4X enclosure allows installation in harsh or outdoor conditions
Problems It Solves
- Original brand transducer is on long lead time or discontinued for the required model
- Transducer output drifts due to vibration or changing mounting angle
- Signal interference from nearby motors or drives causes erratic output
- Need to reverse the output signal direction without changing the controller
- Existing transducer cannot support split range control for multiple valves
- Installation space is too tight for the original transducer size
Application Scenarios
- Replacing a failed Fairchild T7800 transducer on a control valve in a chemical plant with no spare on site
- Installing a transducer in a confined area where space is limited
- Using split range control to sequence a heating and cooling valve from a single controller output
- Requiring a transducer that maintains output stability in a high-vibration pump station
- Installing a transducer in an outdoor valve manifold exposed to rain and dust
- Requiring a transducer with field reversible output for reverse-acting valve control
Who It Is For
- Plant instrument technicians replacing worn or failed transducers on existing valve systems
- EPC contractors sourcing transducers for project builds with tight delivery timelines
- Distributors stocking spares for Fairchild T7800 model replacements
- OEMs needing transducers under their own brand with custom colour and logo
- Maintenance teams upgrading to a more reliable transducer with better noise immunity
Technical Features
- Converts DC 4 to 20 mA input to proportional pneumatic output
- Internal electronic feedback with solid state piezoelectric actuator
- Field reversible output mode for inverse signal response
- Damping adjustment for tuning response to system dynamics
- Split range operation supported for multiple function control
- IP65 and NEMA 4X rated enclosure for indoor and outdoor use
- RFI/EMI protection against electromagnetic and radio interference
- Compact design for use in restricted spaces
- Multiple mounting configurations for flexible installation
Materials and Construction
- Die-cast aluminium housing with corrosion-resistant finish
- Stainless steel internal components for durability
- Piezoelectric ceramic actuator for precise flapper control
- Full material and finish breakdown available 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 die-casting and machining
Assembly of piezoelectric actuator and flapper nozzle system
Integration of electronic feedback circuitry and signal conditioning
Calibration on an air bench across the 4 to 20 mA range
Damping adjustment and split range setup as required
Testing under vibration and electromagnetic noise for RFI/EMI performance
Final inspection and packing in standard or custom cartons
Quality Control
- Every unit is tested for signal-to-pressure accuracy and response time
- All units undergo RFI/EMI and vibration testing before packing
- Photos or video of actual units can be provided on request via WhatsApp
- Faulty units within the 18 month warranty are replaced on photo or video evidence
- Replacements are shipped with the next order or immediately if urgent
Customisation Options
- Customer logo and nameplate marking
- Housing painted in customer colour (black, blue, yellow, or custom)
- Custom carton and inner packaging
- Supplied with or without limit switch box or position transmitter module
- Newly designed shape modules developed to customer drawings
How It Compares With the Alternatives
| TD6000 transducer | The TD7800 has field reversible output and better RFI/EMI protection; the TD6000 lacks field reversibility and has lower noise immunity |
|---|---|
| Pneumatic positioner | A positioner controls stem position; the TD7800 only converts signal to pressure, so it cannot correct for packing friction or actuator load |
| Intelligent digital transducer | A digital transducer adds HART or fieldbus; the TD7800 is a lower cost analog solution for basic signal conversion |
| Mechanical flapper nozzle transducer | The TD7800 uses a solid state piezoelectric actuator, so it is more stable under vibration and does not require frequent recalibration |
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 using the provided brackets or custom mounting hardware
Connect clean, dry instrument air to the supply port and the actuator to the output port
Wire the DC 4 to 20 mA signal with correct polarity
Set the damping adjustment to the middle position for initial tuning
Test the output pressure at 4 mA and 20 mA to verify linearity
For split range, calibrate zero and span to the assigned half of the signal
For field reversible mode, switch the internal jumper or set the function via configuration
TD7800 Electro Pneumatic Transducer FAQ
Will this fit the bracket already on my actuator?
If the actuator currently uses a Fairchild T7800 model, yes. Send a photo of the existing mounting bracket via WhatsApp and we will confirm before you order.
What is the lead time?
Regular quantities normally ship in 2 to 3 days. Large project quantities take 7 to 10 days.
Can I get it in our own colour with our logo?
Yes. The housing can be painted to your colour and the nameplate marked with your logo. Black, blue, and yellow are standard; other colours are painted to order.
What is the difference between TD7800 and TD6000?
The TD7800 has field reversible output and better RFI/EMI protection. The TD6000 lacks field reversibility and has lower noise immunity.
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. It usually travels with your next order, or immediately if the plant is down.
Can I see the actual units before they ship?
Yes. Ask on WhatsApp and we will take photos or film the units in the sample room or warehouse before packing.
Does it support split range operation?
Yes. The TD7800 supports split range operation, allowing one signal source to control two or more functions.
Applications Cases and Guides
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Get A Price on This Model
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