GHM Delta OHM HD50CR, Operating Manual

Page: 13 / 54

HD50CR
- 13 -
V1.0
7 CALIBRATION
The instrument calibrates automatically at regular intervals (default 60 minutes, the in-
terval is configurable) the zero of the differential pressure, temporarily disconnecting
the pressure inputs through an internal solenoid valve.
Via the Fc00 menu (see chapter 7) it is possible to perform a manual calibration in one
or two points. In order to perform manual calibration, it is necessary to unscrew the
two front caps that cover the calibration inputs. To perform zero calibration (Fc05 in
the menu), leave both inputs open. To perform calibration at non-zero values (gain
calibration, Fc08 in the menu), connect the front inputs to a low differential pressure
generator.
The differential pressure zero calibration is also possible via the Modbus Coil register
with address 72 (see chapter 10).
At the end of the calibration or verification, firmly screw the front caps so that the seal
is tight and the inputs are not affected by the external pressure.
Via the Fb00 menu it is also possible to calibrate the relative humidity sensor of the
combined temperature and relative humidity probe at points 33% RH and 75% RH.
Warning: the optional combined relative humidity and temperature probe must be
calibrated in line with the instrument. If the probe is ordered with the instrument, the
probe is already factory calibrated. If the probe is ordered later, the calibration must
be performed by the user via the Fbo00 menu.
Calibration inputs