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(pre change) value : this prompts the operator to re-enter the required new value. It is important that
the Parameter is re-entered, to ensure that the Working register memory in both the Psion and the
MSM400 contain the same data.
If either of the above two Outgoing or Reply Comms Error messages occurs in a Backup menu transfer
between registers, it is advisable to repeat the Backup operation to complete the data transfer, or check
that the memory has been transferred correctly.
The message “NO RESPONSE FROM TRANSMITTER” Indicates a failure of the power on the loop or a
failure of the connection of the SMART interface across the loop or the address of the instrument has
been changed. Connection should be re-established if possible.
The message “LOCKED OUT BY BUS ACTIVITY” indicates there are either two secondary masters on the
bus or a primary master is continuously trying to access an instrument that does not exist.
The message “INCOMPLETE REPLY” indicates that a start of a message was detected but the message
was not completed in the time allowed. This is most likely to be due to a power failure or a loss of
connection.
D.11.0Current Loop Checks and Trimming
Introduction
The MSM400 4-20mA control unit has no customer or service engineering adjustable potentiometers
on the printed circuit boards. All current trimming of the 4mA and 20mA set points is achieved via the
SMART communicator. Because this is a “live” interaction, the access to this function is via the
MONITOR functions and screen on the Communicator.
Select “Current – Output” and the screen displayed is
** CURRENT OUTPUT **
Set current
Trim-maximum
Trim-maximum
These three functions are as follows:
D.11.1Set current
This selection is used for MSM400 transmitters attached to a single 4-20mA loop to check for correct
functioning of all the equipment – the MSM400, the communications and the other loop indicators and
outputs.
By selecting the “Set-current” option the screen prompts the operator to choose a current value for the
loop, for example 12mA.
ENTER NEW VALUE
12-
On pressing “EXE”, the current in the loop is set to this value, and the loop indicators and trips can be
checked for function and calibration. The LCD screen changes to suggest selection of a new value if
necessary. To abort the procedure press ON/CLEAR
CURRENT OUTPUT =
12 mA
ENTER NEW VALUE
-
Some specific error messages are used to prevent the loop current being set outside the valid 4-20mA
limits.