Operation Manual EMGZ 490
15.12.2015
10
4.3
Calibration Procedure
1.
Activate web interface (ref. to chapter 8.1) and call web page „Offset/Calibration
over the web browser” (see chapter 8.3).
2.
Connect volt meter to the voltage output (Fig. 2, terminal 4/5)
3.
Connect first force sensor to the amplifier (see Fig. 2).
4.
Check whether a load in measuring direction (red point) results in a positive volt
reading. If the reading is negative, change signal wires in the corresponding sensor
(Fig. 2, terminals 12/13).
5.
If applicable, connect second force sensor.
6.
Check whether a load in measuring direction (red point) results in a positive volt
reading. If the reading is negative, change signal wires in the second sensor (Fig. 2,
terminals 22/23).
7.
Unload measuring roller by removing material or rope from it.
8.
Click the key „Adjust Offset“.
9.
Load the rope with the defined calibration weight (Fig. 3).
10.
Click the key „Calibrate Gain“. With that the calibration is completed.
4.4
Gain
Depending on the wrap angle of the material on the measuring roller the prevailing
force is not passed one-to-one to the sensors, with the result that the measured
material tension does not correspond to the effective force. In order to account for this
error, the measured force is amplified by multiplier (the Gain). The correction adapts the
measured force with the effective material force. The Gain Factor (V) is calculated with
following formula:
Variables:
F
sys
N=
Installed system force in Newton. This is determined by the number of used
force sensors in the measuring roller. With one force sensor, the system
force is equal to the nominal force mentioned on the label of the sensor. If
the measuring roller contains two sensors the force is twice as large.
F
sys
Digit= System force as a binary value (max. output of A/D-converter). Here it is a
constant with the value 5945. It is independent from the number of used
sensors. From a user perspective, the value corresponds to an input signal of
9mV.
F
ist
N=
Acting force on the measuring system in Newton.
F
ist
Digit= Force measured on the system as binary value (output of A/D-converter).
From a user perspective, the value corresponds to a voltage in mV, that the
amplifier will receive as an input from the force sensors.
F
sys
Digit * F
ist
N
V =
F
sys
N * F
ist
Digit
