March 23, 1998 Design News
From the regional editors
Piezo technique precisely regulates
Uses little power, is vibration
insensitive, and has truezero gauge
by Charles J. Murray, Senior Regional
In some applications, precise pressure regulation is
unimportant. A few pounds per square inch one way or
the other makes little difference. But in many other
applications, precision is critical. There, even a slight
error in pressure measurements may ruin accuracy or
even cause danger.
Problem is, precisely regulating pressure is not always
easy. In particular, many pressure regulators have difficulty
obtaining true zero gauge pressure. For designers of
laboratory equipment, ultrasound welding systems, air
bags, and many other devices, that can be a problem.
To solve it, engineers from Hoerbiger-Origa have developed
a pressure regulator that employs a unique technique.
Known as the Tecno, the new device uses a piezoelectric
"pill," which can almost instantly limit airflow
in response to change in an applied low-power voltage
drive signal. To accomplish that, the piezoelectric
element within the pill changes shape when the desired
drive voltage is applied, thus regulating pneumatic
pressure in an airway.
In the field of pneumatic pressure regulation, Hoerbiger-Origa's
technique represents a dramatic departure from traditional
designs. In the past, most regulators employed one of
two methods: a voice coil or a proportional poppet regulator.
The voice coil, an electromechanical technique, was
often vibration sensitive, and had difficulty achieving
true zero gauge pressure. Poppet-type regulators have
had better luck attaining zero gauge pressure, but typically
require higher power.
In the new design, however, Hoerbiger-Origa claims
that their regulator can consistently achieve
zero gauge pressure without the need for higher power.
What's more, it is not vibration- or position-sensitive.
The key, say its engineers, is the use of the piezoelectric
element. Because it uses no voice coil or solenoid coil,
magnetic energy is not needed to activate it. "Magnetic
energy requires electrical current, and the Tecno uses
very little of that," notes L. Howard Hurley, an
engineer and product manager for Hoerbiger-Origa.
During operation, the Tecno works in three stages.
A control signal (0 to 10V dc or 4-20 mA) is sent to
the device. A comparator measures output pressure and
opens the tiny piezo-ceramic pilot valve, bringing the
output pressure to the command input. The piezo-ceramic,
or "pill," provides a proportional pressure
signal to a larger regulator stage. As the output pressure
rises and the difference between the command and output
reading decreases, the "pill" is commanded
electronically to follow the input signal and change
the output pressure to meet it.
One of the advantages of the system is that it operates
on very small power requirements. Since monitoring and
actuation require so little power, and the pill requires
almost no power, the unit uses less than 0.25 W of power.
As a result, it can operate off 4-20 mA current. It
is also vibration insensitive, and has true zero gauge
"Certain applications must be able to reliably
reach zero gauge pressure," notes L. Howard Hurley,
a product manager for Hoerbiger-Origa. "The Tecno
Additional details?Contact L. Howard Hurley,
Hoerbiger-Origa Corp., 100 West Lake Dr., Glendale Heights,
IL 60139, 630-871-8300.