Glossary · Sensors and measurement
Differential-pressure transmitter
Also known as: DP transmitter, Differential pressure transmitter
German: Differenzdruckmessumformer
In process instrumentation, a differential-pressure transmitter is a transmitter that measures the difference between two pressures and outputs it as a standardized signal, typically 4–20 mA with HART or a fieldbus value.
- Sensors
- Process industry
In one sentence
A differential-pressure transmitter measures the difference between two pressures, used for flow, level and filter monitoring in process plants.
Example
A differential-pressure transmitter across an orifice plate delivers the signal from which the control system calculates steam flow.
How it applies
- Engineering: DP transmitters are used for flow with primary elements such as an Orifice plate, for hydrostatic level in pressurized tanks and for filter or pump monitoring. For flow, the square-root relationship between differential pressure and flow must be applied either in the transmitter or in the control system, not in both.
- Installation: Impulse lines, valve manifolds and, where needed, diaphragm seals influence the measurement. Gas in liquid lines or condensate in gas lines causes errors.
- Maintenance: Equalizing and isolating the transmitter follows a fixed valve sequence to avoid overloading the measuring cell.
- Documentation: Include the manifold operating sequence in the maintenance manual and state where square-root extraction is configured.
Differential-pressure transmitter vs. pressure sensor
A Pressure sensor usually measures against atmosphere or vacuum. A DP transmitter measures the difference between two process pressures.