Operating Manual EMGZ421
5
4
System Description
fig. 1: Basic structure of the EMGZ421 tension measuring amplifier
E421001e
4.1
Functional description
The EMGZ421 is a double channel strain gauge amplifier for a single measuring point.
The material tension can be measured on both sides of the measuring roller
independently.
The 2 force sensors of the measuring point measure the tension force in the material and
transmit the measuring value as a mV signal to the electronic unit EMGZ421. The
electronic unit amplifies the mV signal of each force sensor independently. A sum value
(A+B) and a difference value (A–B) is calculated from the force values of the sensors A
and B. The resulting feedback values are shown in the display in [N]. In addition, the
feedback values are provided at the analogue outputs and can be evaluated by analogue
instruments, a PLC or equivalent devices.
4.2
Force sensors
The force sensors are based on the flexion beam principle. The flexion is measured by
strain gauges and transmitted to the electronic unit as mV signal. Due to the wheatstone
wiring of the strain gauges, the measured value is according also to the power supply. So,
the force sensors are supplied from the EMGZ421 by a very accurate power supply.
4.3
Electronic unit EMGZ421
Common
The electronic unit contains a microprocessor to handle all calculations and
communications, the highly accurate sensor power supply and the signal amplifier for the
measuring value. As operation interface it provides 4 keys, 4 LED’s and a 2x16
characters display in the front of the electronic unit. All inputs are saved in an EEPROM.
The electronic unit has no jumpers or trimmers to keep most accurate long-time and
temperature stability.
Strain gauge amplifier
The strain gauge amplifier provides the highly accurate 4V power supply. A highly
accurate, fixed difference amplifier rises the mV signal up to 10V. This signal will be fed
to the A/D converter. The microprocessor then does all application-specific calculations
with the digitized measuring value (such as offset, gain, low-pass filter, limit switches,
etc).
Summary of Contents for EMGZ421
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