zebris Medical GmbH
FDM Technical Data and Operating Instructions
Page 17/54
3.3
Measuring principle
The system contains a measuring matrix consisting of capacitive pressure sensors that
are arranged in columns and lines running closely next to each other. For determining the
force distribution over the measuring matrix the capacity proportional to the force exerted
is determined for each individual sensor. To do this, the drive logic generates a number
of sinus burst signals equivalent to the number of columns via the column decoder
,
and
transmits them to the respective measuring column. The analog signal coupled into the
shift register over the lines is proportional to the pressure-dependent capacity and is
passed on for further processing to the control and signal-processing electronics and
transmitted to the PC from there and shown on the display.
Schematic circuit diagram of the measuring system
K
a
p
a
z
iti
v
e
M
e
ß
m
a
tr
ix
Spalten-
dekoder
Treiber
Dioden-
schalter
Schiebe-
register
Dioden-
schalter
Schiebe-
register
...
Burstgenerator, Ansteuerlogik
Gleichrichter, Verstärker,
8-Bit ADC
Datenbus
Kalibrierdaten
Kalibrier- Flash
RAM
Optokoppler &
Galvanische Trennung mit
Gleichrichter
PC
externes
AC-Netzteil
entspricht
IEC 601
USB
CPU
Programm-
daten
CPU-internes
Flash
Dioden-
schalter
Schiebe-
register
Dioden-
schalter
Schiebe-
register
...
