NOVUS AUTOMATION
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5
CONFIGURATION
The
NP785 Ultra Low Differential Pressure Transmitter
is configurable by any of its interfaces. Due to the ease of use of the interface, it is
recommended to configure via USB using the
NXperience
software, but the device can also be configured via Modbus RTU by writing directly in
their configuration registers.
The description of the device registers, together with the configuration tables, can be found in the
chapter.
5.1
GENERAL CONFIGURATION
The purchase of the pressure value is done in digital analogue analysis solutions of the internal sensor of the device. You can select the pressure
unit to be used from the following options: mbar, mpsi, in H2O, mm H2O or Pa. Changes in this setting cause transmission limits and alarm set
points to be reverted to the default values, which are the operating limits of the device.
The device also has an
Offset
function and an internal digital filter for treatment of the measured signal. An offset value can be set, which will be
described on the selected pressure unit, to make small adjustments to the output value. The digital filter allows you to set a time interval, in
seconds, to reduce the occurrence of noise effects and peaks of pressure over a faster response.
It is also possible to configure the Modbus RTU communication parameters, such as Baud Rate, parity and slave address of the device.
For purposes of differentiation between units of the same model, an identifier can be configured in the device.
For testing purposes, the device supports forcing differential pressure measurement, analog output and alarm output. For each of these cases, you
can configure a value to be forced and enable or disable the forcing.
5.2
ALARM CONFIGURATION
The
NP785 Ultra Low Differential Pressure Transmitter
has a digital alarm output. The digital output will be activated whenever an alarm
situation is satisfied, except in particular cases defined by some of its settings.
You can configure the alarm operation mode, high and low set points, hysteresis value, state transition timers, error condition and initial blocking.
Alarm configuration can be performed using the
NXperience
software (see the
section ), allowing different modes of operation:
•
Off:
No alarm situation is active.
•
Sensor Error:
While there is some error reading the sensor, the alarm output will remain on.
•
Below Lower Setpoint:
The alarm output will be triggered when the current pressure is lower than the lower set point. To exit the alarm
condition, the differential pressure must be greater than the lower set point plus the hysteresis value.
•
Above Higher Setpoint:
The alarm output will be triggered when the differential pressure is higher than the upper set point. To exit the alarm
condition, the differential pressure must be lower than the lower set point minus the hysteresis value.
•
Intra-range:
The alarm output will be activated when the differential pressure is higher than the lower set point and lower than the upper set
point. To exit the alarm condition, the differential pressure must be greater than the upper set point plus the hysteresis value or lower than the
lower set point minus the hysteresis value.
•
Extra-range:
The alarm output will be activated when the differential pressure is higher than the set point higher or lower than the lower set
point. To exit the alarm condition, the differential pressure must be less than the upper set point minus the hysteresis value and higher than the
lower set point plus the hysteresis value.
In addition to the alarm operation modes, other parameters, which do not apply to the Sensor Error mode, can be configured to refine the behavior
of the alarm output:
•
Initial Blocking:
This parameter determines the use of the alarm output lock soon after the device is started. After initialization, a non-alarm
condition is required for the alarm output to be enabled.
•
Error Condition:
The status of this parameter determines whether the alarm output will remain on or off in case of sensor failure.
•
Hysteresis:
This parameter stores the pressure value that, with the values of the set points, determines the limit value to leave the alarm
situation.
Fig. 07
shows the conditions for alarm activation and deactivation.
The alarm output can be timed by means of the
Time On
and
Time Off
parameters. For a given state transition to occur, the device must remain in
the new state for a period of time equal to the one configured in the respective transition parameter. These values are initialized to 0 by default.
Extra-range
mode is the default mode of alarm output. The default values of the set points, in turn, are the operating limits of the device. Any
changes in the pressure unit configuration readjust the values of the set points to the operating limits.
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