Emerson MSM400 manual Current Output ** Set current Trim-maximum Trim-maximum

(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.

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