How Does a DP Cell Work?

••• grafvision/iStock/GettyImages

Measuring the pressure exerted by a column, or head, of liquid in a vessel is one of the oldest and most common methods of measuring liquid level. The advent of “smart” dp or dP cells, or transmitters, means renewed interest in this tried-and-tested technique of measuring differential pressure.


A typical dp cell works by applying differential pressure to either side of a metal diaphragm immersed in non-conducting oil. The movement of the diaphragm changes the electrical capacitance--the ratio of charge to potential difference--of the cell and, in turn, the electric output signal.

Closed Vessel

If the pressure in a closed vessel changes, the change applies equally to both sides of a dp cell. A dp cell responds only to changes in differential pressure--the difference in pressure between two points--so it remains unaffected by a change in static pressure. It therefore responds only to change in the liquid level.

Open Vessel

In an open vessel--one that is not under pressure or a vacuum--the vessel is connected to a dp cell on the high-pressure side via a pipe. The low-pressure side is left open to the atmosphere.

Related Articles

How to Fix a Barometer
Why Do Chloroplasts Move in Elodea?
What Is an Instrument Which Measures the Pressure of...
What Is a Differential Manometer?
How to Convert mm Hg to in Hg
How to Perform a Manometer Test
How Do Piezoresistive Pressure Sensors Work?
How a Solenoid Pump Works
Living Cell Characteristics
What Are the 2 Types of Barometers?
Types of Mixing Valves for an Oil Furnace Boiler
How to Calculate the Horsepower of a Compressor
Why Do Chloroplasts Move in Elodea?
How to Test a Thermistor
The Definition of a Convection Cell
What Is a Manometer?
How to Figure GPM Water Flow on an Existing Chiller
Types of Hygrometers
Why Do Plant Cells Have Cell Walls As Well As Cell...
Who First Discovered Viscosity?

Dont Go!

We Have More Great Sciencing Articles!