Piezoelectric Measurement Chains - HBM MP85A Operating Manual

24
CAUTION
The differential signal of the measurement signal and the zero index si-
gnal must each be minimum 1.2 V.
The voltage to measurement ground must not exceed 14 V in any line. If
necessary, the voltage must be reduced via a voltage divider.

3.4.4 Piezoelectric measurement chains

The inline charge amplifier model CMA or CMD is required for operating
piezoelectric sensors on the MP85A process controller. The charge amplifier
is supplied externally with 24 VDC and is available from Pin 7 and 8 of the
screw terminals 5 and 6 of the MP85A process controller (see Chapter 3.4.3,
Active sensors, Fig. 3.7).
Internal or external voltage in the MP85A process controller can be selected
via switch S1. The device must be opened to do this (see Chapter 4) and the
switch S1 set to "24V external".
Piezoelectric
force transducer
Fig. 3.8: Block diagram of the piezoelectric measurement chain
The MP85A process controller measurement channel must be set to 10 V
(PME Assistant menu: Transducer). A reset on the charge amplifier must be
carried out before starting a measurement (Pin 3) MEASURE / RESET. With
an input voltage of 0 V at PIN 3, the charge amplifier is in the measurement
HBM
CMA charge amplifier
MP85A process controller
Supply voltage
18 to 30 V
DC
0 V
DC
RANGE 1 / RANGE 2
MEASURE / RESET
Output voltage
−10 ... +10 V
DC
0 V
DC
TEDS
A2392−5.0 en