| Installation, Operation & Maintenance Manual |
MSL600 | IP262/Z0, Rev. AB |
February 2012 | |
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5.4 mA current output parameters
The operation of the current output is programmed by four parameters and is always controlled by the sludge blanket level.
The current output parameters are found in SETUP – OUTPUT – CURRENT OUTPUT.
The parameters are as follows:
Low range val (Lower range value)
This parameter allows the user to reference the programmed minimum current output (0 or 4mA) to any point in the programmed blanket level measurement range.
The default condition is that the programmed minimum current corresponds to 0m (0 feet), the tank bottom.
Up range val (Upper range value)
This parameter allows the user to reference the maximum 20mA current output to any point in the programmed blanket level measurement range.
The default condition is that 20mA corresponds automatically to the programmed tank depth parameter less the top blanking distance. This level is programmed by the tank depth parameter which by default is set to be 7.000m (23.00 feet). The 20mA level for default settings therefore corresponds to a sludge blanket level of 6.7m (22.1 feet)
Alarm action
This parameter is selectable from a list and determines the action to be taken by the current output under alarm conditions.
The allowed actions are:
•Go to 3.6mA
•Go to 21mA
•Hold last reading
This parameter sets the current output range from a list to be either
5.5Current output adjust
The current output is calibrated in the factory and should not require any adjustment.
However, if required, it is possible to adjust the 4mA and 20mA points using a calibrated meter. This is done by following the procedure detailed below:
1.Connect a milliammeter to the terminal block marked CURRENT OUT ISOLATED between the 0V and the IO connections.
2.Put the system off line so that the ‘Go Off line?’ padlock is open.
3.Access the SETUP – SYSTEM – TEST – CURRENT OUTPUT menu.
4.Select either the “4mA out adjust” or the “20mA out adjust” and press .
5.Read the actual current on the calibrated meter.
6.Enter this value in the chosen parameter and press .
7.Check that the actual current is now exactly 4mA or 20mA.
For diagnostic purposes the current output can be driven to any value between 4mA and 20mA by accessing SETUP – SYSTEM – TEST – CURRENT OUTPUT – Set current.
With a suitable meter connected to the current output terminals a value can programmed on the control unit and the same value will appear on the meter.
This programmed current will remain until the ‘Go On line?’ padlock is closed.
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