4 – The Autocalibrating Function (ACF)
The CPD8000 measuring force cell response to the force,
which is applied to it, may drift with time. In addition to this
drift which is due to the ageing of the measuring force cell,
a low short-term drift may appear: this is an evolution of the
measuring force cell response according to the change of
the environmental parameters, above all ambient
temperature and relative humidity.
To curb these drifts,
the CPD8000 is fitted with an Auto
Calibrating
Function
(ACF)
coupled
with
an
Environment Monitoring Module (EMM)
.
The use of the ACF enables the measuring force cell to
easily free from this drift by readjusting its deviation
according to the new environmental conditions, even when
the measuring head is fitted.
The ACF consists in an
automatic loading of an internal
standard mass
which can be easily loaded by pressing a
key located on the front panel, or from a remote computer.
By applying the standard mass, you readjust the deviation
of the measuring force cell according to two points: zero
and the mass generated force value (i.e. the full scale
value).
You can optionally use a set of external standard masses
in order to check the measuring force cell linearity over 5
points. These masses can also be used to run an external
calibration.
5 – The Environment Monitoring Module (EMM)
In order to determine whether it is worthy to use the ACF,
the CPD8000 is equipped with an Environment Monitoring
Module which
consists in 3 sensors for ambient
temperature,
relative
humidity
and
barometric
pressure
, and their electronic components.
After the calibration, the EMM keeps on monitoring the
evolution of the ambient conditions in real time.
If these conditions vary
in proportions that might noticeably
alter the measuring performance, the CPD8000 displays a
warning flag to advise the user to command the ACF in
order to readjust the dynamometer to the new operating
conditions. The warning flag is also sent to the command
software if the CPD8000 is operated from a remote
computer.
When the ACF is in use, the environment conditions, for
which the measurements carried out by the measuring
force cell are valid, are measured by the EMM and stored
in the internal memory
Therefore, the EMM monitors the difference between the
conditions stored during the calibration, at t0, and the
conditions measured when the operation took place, at t+1
.
The sensors with which the EMM is fitted are not used for
their accuracy and long-term stability, but for their short
term repeatability.
Measuring force cell
Computer
connection
Internal standard mass
EMM sensors
Page 4 of 8
Desgranges & Huot WIKA Data Sheet CPD8000 04/2012
