Delta OHM HD40.2, Руководство пользователя

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HD402TR
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V1.0
3 INSTALLATION
The sensor and the electronics are housed in a rugged plastic case with IP 65 protec-
tion degree. By opening the lid, 3 mm diameter holes are available so to allow secur-
ing the base of the instrument directly to a panel or to the wall.
The instrument can be mounted in any position, but typically it is secured on a vertical
wall with the pressure inputs facing down.
In the model HD402TR1L, an auto-zero circuit periodically automatically equalizes the
differential pressure at the input of the sensor and corrects the offset due to the
mounting position or sensor aging. In the other models, the deviation of the zero can
be manually corrected as follows:
• Disconnect both the tubes from the pr and – inputs.
• Press B1 and B2 buttons at the same time until the ALARM red LED lights up (if it
was not already on because of an alarm condition) and the instrument displays
the model information and the UP and DOWN arrows on the left of the LCD.
• When the instrument returns to the measurement mode displaying zero read-
ing, reconnect the tubes to the pressure inputs.
If necessary, the manual auto-zero procedure can be performed also in HD402TR1L
(in this case it is not necessary to disconnect the tubes from the pressure inputs).
Except for HD402TR1L (in which the auto-zero procedure is periodic and automatic), it
is recommended to follow the auto-zero procedure at least once a year under normal
operating conditions.