A major group developing sensor solutions for
industry is operating at the Leti, a laboratory
within the French Commissariat d’Energie
Atomique. The Leti is a laboratory where
approximately 86 per cent of projects are
carried out in collaboration with industry and
more than 50 per cent of funding is from
industrial partners. Split between locations in
Grenoble and Saclay, a Paris suburb, the Leti
sensor activity employs some 70 people and
works on medical and environmental applica-
tions as well as automotive, aerospace,
defence and automation. The largest group,
composed of about 30 researchers, works on
mechanical and chemical sensors.
One of the projects the Leti is working on is
a miniature sensor to detect methane in coal
mines and thus anticipate fire-damp explo-
sion. While competitors have developed
systems that function using a heat resistor
attached to a membrane, the Leti’s sensor is
the only one based on a “floating” structure
and the only one to go up to 900°C, the labo-
ratory claims. The project is being undertaken
in partnership with the Ineris, a development
laboratory attached to France’s National
Institute for Mining Research.
The miniaturized Leti sensor works on the
same principle as existing methane detectors,
which is that a platinum filament is heated up
by passing a short pulse of electric current
through it. The current is enough to raise the
platinum to above 650°C, the temperature at
which the platinum causes any methane in the
air to burn, and that raises the temperature of
the filament even further, thereby increasing
its resistance, a factor that can be measured to
give an indication, or not, of the presence of
methane.
The active component, which is the “float-
ing” part of the Leti sensor, measures 2mm ×
52 microns × 6 microns. It is composed of a
thin-layer platinum filament in the form of an
accordion structure, and is attached to a
quartz substrate measuring 3mm × 3.8mm.
However, the quartz substrate has been hol-
lowed out so that the active component hangs
in mid-air. Because platinum is difficult to
etch, the “lift-off” technique is used for the
fabrication of the filament on the quartz
substrate.
Using such a structure, the filament heats
up very quickly – taking just 10ms to reach
900°C – which means that measurements can
be taken more frequently and that the sensor
will last longer than those in current use,
38
Sensor Review
Volume 16 · Number 2 · 1996 · pp. 38–40
© MCB University Press · ISSN 0260-2288
Anna Kochan
The author
Anna Kochanis European Correspondent for
Assembly
Automation, Industrial Robot, Service Robot
and
Sensor
Review.
Abstract
Highlights some of the projects being carried out by the
Leti, a laboratory within the French Atomic Energy Com-
mission. Specifically looks at the development of a minia-
ture sensor to detect methane in coal mines; pressure
sensors in the automotive industry; the development of a
miniature sensor which triggers airbag inflation in vehi-
cles; and a sensor to measure pressure at high tempera-
tures for use within the aeronautics industry.
Author’s address
Author’s name here
Address 1
Address 2
Address 3
Address 4
Address 5
e mail:insert here
Features
Sensor research at the
French Atomic Energy
Commission