Fema M Series, User Manual, Page: 10 / 36

FEMA ELECTRÓNICA . SERIES M . M60-LC
10
1.12.2 Initial set-up
Before starting to configure the instrument, identify the pa -
rameters of the load cell, at the manufacturers datasheet
(see
Table 5)
. If the parameters are not know, leave the instrument
with the default values.
Load cell
parameters
Default values
Sensitivity 2 mV/V
Nominal weight 1000 Kilos
Excitation voltage 10 Vdc
Table 5 - Parameters of the load cell
For an accurate measure, the instrument needs to correctly
configure its parameters for the particular load cell connect -
ed. The configuration procedure has a first theoretical step
and a second empirical step. The third and final step will set
the ‘system zero’ of the instrument.
Theoretical configuration of the load cell
The theoretical parameters are configured at the ‘
Parameters
of the cell ’ (‘ cELL ’) menu.
• at the ‘ Decimal point ’ (‘ dP ’) parameter, place the decimal
point according to the resolution you want to see.
• at the ‘ Nominal weight ’ (‘ LoAd ’) parameter introduce the
nominal weight of the load cell. The value is entered with the
resolution configured in the parameter above.
• at the ‘ Sensitivity ’ (‘ MV.V ’) parameter, introduce the value
of the cell sensitivity.
• at the ‘ Excitation voltage ’ (‘ V.EXc ’) parameter, select 5 or
10 Vdc. (The ‘LAb’ value enables the laboratory mode, for di -
rect measure from a millivolt generator instead of a load cell
(see section 1.16.5)).
Example : load cell with 1.95 mV/V sensitivity and a nominal
value of 5 Kg and power 5 Vdc. To read in grams with a deci-
mal point, configure the theoretical parameters as indicated
below :
Decimal point : XXXXX.X
Sensitivity : 1.95 mV/V
Nominal weight : 5000.0
Excitation voltage : 5 Vdc
When the theoretical values are configured, leave the config -
uration menu. Apply a ‘ system zero’ . Force a tare, and place
different weights to check if the reading is correct. If it is not
correct, apply the empirical configuration and again the ‘ sys -
tem zero ’.
Empirical configuration of the load cell
The second part of the load cell configuration is an empiri -
cal process of field correction. The instrument will detect and
correct the individual deviations of this particular load cell.
For the empirical configuration you will need access to two
weights : a low weight, as small as possible (it can be the cell
without weight) and a high weight as close as possible to the
nominal weight of the cell.
In each case the meter will be informed of the real weight
applied to the cell in order to correct and compensate for the
measured deviations at the signal. Both corrections are need
(high and low) for a correct configuration of the load cell.
• low weight correction : place the load cell without weight
or with the smallest weight possible, and access the ‘ Low
weight correction ’ (‘ F.Lo ’) menu. Press key SQ (‘
<
’), intro -
duce the value of the weight and press again SQ (‘
<
’). The
instrument will flash shortly and return to the menu entry
‘ Low weight correction ’ (‘ F.Lo ’).
• high weight correction : place the load cell with a weight
closest to nominal and access the ‘ High weight correction ’
(‘ F.hI ’) menu. Press key SQ (‘
<
’), introduce the value of the
weight and press again SQ (‘
<
’). The instrument will flash
shortly and return to the menu entry ‘ High weight correc-
tion ’ (‘ F.hI ’).
Once both corrections are applied, leave the configuration
menu. Force a tare, and place different weights to check that
the reading is correct. As a last step, assign the ‘system zero’ if
you want to access gross weight and net values.
Assign the ‘system zero’
This is a necessary and important step for a correct measure -
ment with a load cell.
• assign the ‘system zero’ : place the load cell without weight
or with the weight that will be considered as ‘zero’ and access
the ‘ System zero ’ (‘ S.ZEr ’) parameter. Press key SQ (‘
<
’). The
instrument will flash shortly and return to the menu entry
‘ System zero ’ (‘ S.ZEr ’).
The empirical configuration of the load cell recalcu -
lates and updates the theoretical sensitivity value
(‘ Sensitivity mV/V ’ (‘ MV.V ’) parameter). Manual
modifications of this parameter will modify the configura -
tion of the cell. To prevent accidental modification con -
sider the activation of the ‘ password ’ function (see section
1.12.17)
.
!
Once the load cell has been correctly configured,
and the reading of the instrument is correct, it is not
necessary to access again this part of the configura -
tion menu. If you need to scale the reading to different units,
use the ‘ Scale factor ’ (‘ ScL.F ) parameters at the ‘Advanced
configuration’ menu
(see section 1.12.7) .
!