Intelligent Digital Display Pressure Transmitter with Alarm Relay
1. Why You Need It
Operators need to read pressure at the point of measurement and react immediately when it crosses a limit — without walking back to the control room. This intelligent transmitter integrates a backlit LCD with multi-unit readout (MPa, kPa, bar, psi, kgf/cm²) and a configurable alarm relay, so it both displays and acts on pressure locally. With HART 7 communication, IP67 protection and local pushbutton configuration, it is a practical smart-plant instrument for gas and liquid process lines.
2. Working Principle
A strain-gauge or capacitive sensor measures process pressure and converts it to a 4-20 mA signal. An integrated microcontroller drives the backlit LCD to show the value in selectable engineering units and continuously compares it against user-set alarm limits. When the pressure crosses a limit, the relay energizes to trigger an alarm or control action. Local pushbuttons allow on-site configuration of range, units and set points without a handheld communicator.
3. Key Advantages
- Integrated backlit LCD display
- Multi-unit readout (MPa, kPa, bar, psi)
- Configurable alarm relay output
- HART 7 protocol
- IP67 protection
- Local pushbutton configuration
- Gauge / absolute / sealed gauge
- 316L wetted materials
- 4-20 mA 2-wire output
- 1/2 inch NPT process connection
Common Pain Points & Solutions
| Problem | Conventional Issue | Our Solution | Result |
|---|
| Need local pressure reading | Control-room-only readout | Backlit LCD on transmitter | Local, at-a-glance reading |
| Alarm on pressure limit | Separate switch needed | Integrated alarm relay | Single device, display + alarm |
| Unit conversion confusion | Single-unit displays | Multi-unit readout | Read in required units |
| Field configuration difficult | Handheld communicator required | Local pushbuttons | On-site setup, no extra tools |
Application Cases
Industry: Plant Utilities
Application: Compressed air system pressure
Medium: Compressed air
Pressure Range: 0-1.0 MPa
Operating Temperature: 0-50 °C
Installation Environment: Utility room
Customer Challenge: Local + remote pressure monitoring
Previous Problem: No local display available
Solution: LCD transmitter with alarm relay
Installation Location: Air receiver
Result: Immediate local reading and alarm
Industry: Water Treatment
Application: Filter differential pressure
Medium: Water
Pressure Range: 0-0.6 MPa
Operating Temperature: 5-40 °C
Installation Environment: Washdown area
Customer Challenge: Detect filter clogging
Previous Problem: Manual inspection only
Solution: IP67 display transmitter, bar readout
Installation Location: Filter skid
Result: Early clog detection, washdown safe
Industry: Process
Application: Gas line pressure monitoring
Medium: Process gas
Pressure Range: 0-1.6 MPa
Operating Temperature: 10-60 °C
Installation Environment: Process area
Customer Challenge: Stable pressure with diagnostics
Previous Problem: Analog-only signal
Solution: HART 7 absolute transmitter
Installation Location: Gas header
Result: Smart diagnostics, stable control
Industry: Machinery
Application: Hydraulic system pressure
Medium: Hydraulic oil
Pressure Range: 0-30 MPa
Operating Temperature: 10-70 °C
Installation Environment: Machine enclosure
Customer Challenge: Compact local indication
Previous Problem: Bulky instruments
Solution: Sealed gauge transmitter, 1/2 NPT
Installation Location: Hydraulic manifold
Result: Compact install, local readout
Technical Specifications
| Specification | Value |
|---|
| Display | Backlit LCD, multi-unit |
| Pressure Type | Gauge / Absolute / Sealed Gauge |
| Output | 4-20 mA 2-wire + alarm relay |
| Protocol | HART 7 |
| Power Supply | 24 V DC |
| Protection | IP67 |
| Wetted Material | 316L stainless steel |
| Process Connection | 1/2 inch NPT |
FAQ
Q: What does the display show?
The backlit LCD shows the measured pressure in selectable units including MPa, kPa, bar, psi and kgf/cm². The multi-unit readout lets operators view the value in whichever unit is most meaningful for their process, and the backlight ensures readability in dark or outdoor locations. The display provides an immediate local reading without needing a separate indicator or a trip to the control room.
Q: Does it have an alarm output?
Yes, it includes a configurable alarm relay. When the pressure crosses a user-set high or low limit, the relay energizes to trigger an alarm, light, pump or valve action locally. This integrated alarm removes the need for a separate pressure switch, reducing hardware, wiring and installation cost while providing immediate response at the point of measurement.
Q: Can it be configured in the field?
Yes, local pushbuttons allow on-site configuration of range, engineering units and alarm set points without a handheld communicator or laptop. This is convenient for commissioning and for adjusting limits as process conditions change. HART 7 is also available for remote configuration from the control system when desired.
Q: What communication does it support?
It supports HART 7 protocol over the 4-20 mA loop. HART enables remote configuration, calibration and diagnostics, and integrates with asset-management systems. The 4-20 mA signal carries the primary measurement, while the digital HART channel provides device status, diagnostics and configuration without additional wiring.
Q: What is the protection grade?
The housing is IP67 rated, protecting against dust ingress and the effects of temporary immersion in water. This makes the transmitter suitable for outdoor installations, washdown areas and dusty industrial environments, where reliable operation despite moisture and contamination is required.
Q: What wetted materials are used?
The wetted parts are 316L stainless steel, providing good corrosion resistance for gas and liquid process media. 316L is the standard for general industrial service, offering a balance of corrosion resistance, strength and cost. For highly aggressive media, confirm compatibility or consider a diaphragm material upgrade.
Q: What pressure types does it measure?
It measures gauge, absolute and sealed gauge pressure. Gauge pressure is referenced to atmosphere and is the most common for process lines. Absolute pressure is referenced to vacuum, and sealed gauge uses a fixed internal reference. The choice depends on the application and the reference point the control system requires.
Q: How is it connected to the process?
The transmitter uses a 1/2 inch NPT process connection, the standard for many industrial gas and liquid lines. The electrical connection is an M12 connector, providing a secure, quick-disconnect wiring interface. The combination allows straightforward installation and easy removal for calibration or replacement.
Q: Why combine a display with a transmitter?
Combining a local display with a transmitter gives operators an immediate reading at the measurement point while still sending the 4-20 mA signal to the control system. This dual capability improves situational awareness, speeds troubleshooting and reduces the need for separate local indicators — lowering cost and simplifying installation.
Q: Where is it used?
It is used on compressed air systems, water treatment filter skids, gas headers, hydraulic systems and other process lines where local pressure indication and alarm capability are valuable. It suits plants adopting smart instrumentation, where HART diagnostics and local configuration reduce commissioning and maintenance effort.
