What is the difference between absolute and differential pressure transmitter?
The difference between absolute pressure transmitters and differential pressure transmitters lies in how they measure pressure and their applications:
Absolute Pressure Transmitter
Reference Point: Measures pressure relative to a perfect vacuum (zero pressure).
Working Principle: Contains a sealed vacuum chamber as a reference, ensuring that the reading is independent of atmospheric pressure variations.
Formula: Pabsolute=Pmeasured−Pvacuum (0 bar)
Applications:
Used in barometric pressure measurement.
Vacuum systems and altitude monitoring.
Meteorological and aerospace applications.
Processes where atmospheric pressure variations could affect accuracy.
Differential Pressure Transmitter
Reference Point: Measures the difference between two pressure points (High-Pressure Side vs. Low-Pressure Side).
Working Principle: Uses two pressure ports to compare pressures and provide the difference as an output.
Formula: Pdifferential=Phigh−Plow
Applications:
Flow measurement using orifice plates, Venturi tubes, and pitot tubes.
Level measurement in closed tanks.
Monitoring pressure drop across filters, strainers, or heat exchangers.
Pump and compressor efficiency monitoring.
Key Differences between Absolute Pressure Transmitter and Differential Pressure Transmitter
| Feature | Absolute Pressure Transmitter | Differential Pressure Transmitter |
|---|---|---|
| Reference Point | Full Vacuum (0 bar) | Another pressure source(normally atmospheric) |
| Ports | Single pressure port | Two pressure ports (high & low) |
| Compensates for Atmospheric Pressure Changes? | Yes | No |
| Typical Applications | Barometric, vacuum, altitude measurement | Flow, level, filter monitoring |
The difference between absolute and differential pressure transmitters lies in the reference point they use to measure pressure:
1. Absolute Pressure Transmitter
- Reference Point: Measures pressure relative to absolute zero pressure (a perfect vacuum).
- Usage: Used in applications where atmospheric pressure variations need to be eliminated, such as:
- Barometric pressure measurement
- Vacuum systems
- Altitude and weather monitoring
- Semiconductor manufacturing
- Example: If the absolute pressure is 2 bar, it means the pressure is 2 bar above a perfect vacuum.
2. Differential Pressure Transmitter
- Reference Point: Measures the difference between two pressures (high and low side).
- Usage: Used in applications where monitoring the pressure difference between two points is necessary, such as:
- Flow measurement in pipes (with orifice plates, Venturi tubes, or flow nozzles)
- Level measurement in closed tanks
- Filtration system monitoring (detecting filter clogging)
- Example: If the pressure on the high side is 5 bar and the low side is 3 bar, the differential pressure reading will be 2 bar.
Key Difference
- Absolute Pressure Transmitters measure pressure against a vacuum, useful in precise scientific and atmospheric applications.
- Differential Pressure Transmitters measure the pressure difference between two points, commonly used in industrial process control.