User's Guide ______________________________________________________________________
60 __________________________________________________________________ M210667EN-C
For maintenance purposes, the PWD provides a user interface that can be
accessed in the following ways:
- Selected commands are accessible through the LT Maintenance
Interface (see section LT Maintenance Interface on page 132).
- The full PWD command set can be used when connected to the PWD
Maintenance Interface.
Software Descriptions
Besides the PWD forward scatter sensor and the optional LM21
background luminance sensor, LT31 contains the following intelligent
units:
- The master CPU
- The measurement CPU of the transmitter
- The measurement CPU of the receiver
Master CPU
The master CPU is located in the interface unit of the LT31 receiver
limit.
The main tasks of the master CPU are as follows:
- Collect raw data from all connected intelligent units
- Carry out all calculations and algorithms
- Self-check and alarm/status report
- Host
interfacing
- Maintenance/user
interfacing
Measurement CPUs
The CPU board of the measurement units of LT31 transmitter and
receiver are similar and contain exactly the same software. During the
power on procedure the operation mode is automatically set to
transmitter or receiver mode depending on the connected hardware.
The main tasks of the measurement CPU and the associated software are
the following:
- Collecting raw data and calculate 5-second average values
- Distributing data on the request of the master CPU
- Carrying out actions on the request of the master CPU