By Mike Horton, CTO, ACEINNA
What Design Engineers Need
to Know about Next-Generation
Differential Pressure Sensors
Discover the variety of differential pressure sensors are the market and the key factors to consider when selecting one for
Pressure sensors today are almost as common as op-amps were in the 1990s. Applications span
from consumer smartphones to precision control
instrumentation in the world’s most sophisticated
process plants. Pressure sensors themselves are not
new, but the technology inside and variation of devices
are ever expanding. This article helps design engineers
get up to speed with the latest in differential pressure
A DP sensor is a special type of pressure sensor that
measures the change in pressure across two ports on a
device. This is different from a static or absolute pressure
sensor that would measure pressure using just one port.
A barometer or altimeter is the classic example of an
absolute pressure sensor, whereas an aircraft airspeed
sensor is the classic example of a DP measurement device.
DP is also a measure of flow; hence, many applications
describe their requirement as a flow measurement.
DP measurement for low-pressure ranges is often
used in medical, industrial, and Internet of Things (Io T)
applications. DP is measured in units of Pascals (Pa)
or inches of water column (inH20)—1.0 Pa = 0.00402
inH20. A high-accuracy DP measurement is one that
achieves an accuracy better than 0.1 Pa.
Some typical end applications of flow and DP include:
1. Medical Devices: For example, in-home, small
machines known as continuous positive air pressure
(CPAP) use flow sensors to help regulate airflow to
the user, which helps treat sleep apnea.
2. Residential Metering: Flow sensors are often used for
measurement and accounting of natural gas flow into
homes and building throughout the world.
3. Appliances: DP can be found in residential,
commercial, and industrial gas burners to control
gas flow into a burner system. They are also found
in HVAC systems to implement zone control based
heating and cooling.
4. Industrial Components: Valves, pumps, and
other basic building blocks of the industrial world
often require accurate and reliable flow and DP
5. Io T: The Io T has created a new class of smart-
consumer devices for air quality and airflow
measurement needing high precision. These devices
combine particle counters with airflow measurement
to gauge the quantity of tiny PM2.5 particles in the
air. Large quantities of PM2.5 particles have been
shown to cause serious health ailments in children.
Recently, new technology has enabled very low-cost, but
accurate DP measurement using “Thermal MEMS” sensing.
MEMS (Micro-electrical Mechanical Systems) is a set of
widely used processes to create structures in silicon. The
thermal principle of operation is explained below (Figure
1). Thermal MEMS pressure sensing is best understood by
examining a simple diagram of its operation.
Figure 1: MEMS flow sensor theory of operation.
A micromechanical MEMS flow sensor can be made
with one or more heaters and temperature sensors.
One simple way is to have a heater surrounded by two
temperature sensors placed symmetrically at the left
and right side. When the heater (actually a resistor) is
warmed by passing currents, a steady state temperature
profile is built up around the heater. With the symmetry,
two temperature sensors detect the same temperature
when the gas (media) is not flowing. When the gas is