MCE2035: User manual
Version: 2011-05-17, rev.: 0a
Page: 12
6) DATA PROCESSING
6.1 Zeroing, calibration and weight calculation
Calculation of system weight(s) is done by addition of the weight registers for the load
cells belonging to the system. This is explained below.
Note
that the result is only valid if
all status registers for the load cells in question indicate no errors. It should also be noted
that it is up to the master to ensure the usage of consistent load cell data when calculating
the system weight (the used data should come from the same telegram).
6.1.1 Zeroing of weighing system
Zeroing of a weighing system (all load cells in the specific system) should be performed as
follows, taking into account that no load cell errors may be present during the zeroing pro-
cedure:
1)
The weighing arrangement should be empty and clean.
2)
The Profibus-DP master verifies that no load cell errors are present, after which it reads and stores
the actual weight signals for the load cells of the actual system in corresponding zeroing registers.
LcZero[x]=LcSignal[x]
3)
After this the uncalibrated gross weight for load cell
X
can be calculated as:
LcGross[
X
] = LcSignal[
X
] – LcZero[
X
]
6.1.2 Corner
calibration of weighing system
In systems where the load is not always placed symmetrically the same place (for example
a platform weight where the load can be placed randomly on the platform when a weighing
is to take place), a fine calibration of a systems corners can be made, so that the weight in-
dicates the same independent of the position of the load. This is done as follows:
1)
Check that the weighing arrangement is empty. Zero the weighing system.
2)
Place a known load (
CalLoad
) directly above the load cell that is to be corner calibrated.
3)
Calculate the corner calibration factor that should be multiplied on the uncalibrated gross weight of
the load cell in order to achieve correct showing as:
CornerCalFactor[x] = (CalLoad)/(LcGross[x])
After this the determined corner calibration factor is used to calculate the calibrated gross weight
of the load cell as follows:
LcGrossCal[x] = CornerCalFactor[x] * LcGross[x]
