Walchem WebMaster, Инструкция по эксплуатации

Страница: 78 / 178

74
6.9 Flow Meter (4-20 mA) Input Menu
(Only appears if a 4-20 mA input option card is installed, and a Flow Meter pull-down is selected
in the 4-20 mA Input section of the Start Up page)
Backup Sensor Mode
The redundant sensor algorithm will allow the user to define a primary sensor to use for control
and a backup sensor. If the primary sensor goes invalid, the backup sensor will automatically take
over control, and the sensor error alarm will activate. If the sensors don’t match each other within
user-defined limits but both are valid readings, control will stop and a Sensor Deviated alarm will
activate. If the backup sensor goes invalid while the primary sensor is OK, control continues but
the sensor error alarm will activate. If both sensors are invalid, control stops and the sensor error
alarms activate.
To select this sensor as the backup sensor, click the Backup radio button, then click on the Submit
button at the bottom of the page. The page will reload showing the status of the sensor as Backup,
and offer additional menus:
Primary Sensor Assignment
This menu only appears if the Redundant Sensor Setting is Backup.
Use the pulldown arrow to select the sensor to use as the primary control sensor. All sensors of the
same type as the backup sensor will appear in the pulldown list.
Deviation from Primary Sensor
This menu only appears if the Redundant Sensor Setting is Backup.
Type the maximum allowable difference between the two sensor readings. If this deviation is
exceeded, then control of any outputs using the sensor will stop and an alarm activated.
Input
This column displays all of the 4-20 mA inputs that are defined as Flow Meter type.
Custom Name
Type in the text box the customer name that you may want to give to this flow meter.
Rate
This column will display the flow rate through (or past) the flow meter.
Present mA
This column will display the mA output of the flow meter.
4 mA=
Type the flow rate at which the flow meter will send a 4 mA signal into the text box. This will
generally be at 0 gallons or liters/minute.