User Manual

Siemens Building Technologies CM2N8882en / 02.2000
Landis & Staefa Division 3/8
Measuring points are analogue input information points. Any status changes directly
result from the processes in the building services system.
Measuring points are also referred to as measured value points or analogue input (AI)
points.
For measuring points, the measured value transmitters are located in the plant. These
transmitters supply analogue (modulating, continuous) measuring signals in the form of
electrical resistance, current, or voltage signals. Measured value transmitters may be
passive (resistance sensors) or active devices (measuring transducer).
In VISONIK systems, measured value modules acquire the measuring signals and
conduct analogue to digital conversion (A/D conversion).
The VISONIK BPS periodically polls the digitized measuring signals (raw measured
values) via the P-bus and converts them to the corresponding physical variables.
Example: A resistance value is converted to the relative temperature °C.
D
A
A
D
1 2
VISONIK BPS
8882Z03E
bidirectional
data line
Measured value points
in the plant
P-bus
Communication
partner
Preparation
Processing
Measured value module
Depending on the programming, measuring signals may trigger the following functions in
VISONIK:
Function Example
Reports Show plant image of the management
station due to violation of the measured
value limit
Alarming local and/or central Violation of the upper or lower measured
value limits
Counting the frequency of measured value
changes and/or limit value violations
Fault analysis
Logical link to limit value violations and fault
states
Frost situation
Mathematical operations in COLBAS Mean value calculation for several
measured values or for a specific period
of time
Switching and positioning commands as a
response to measured value changes
Sustained plant operation during OSTP
setback phase
Measured value activation as control, fault,
or reference variable for DDC control
Room, outside, supply air temperature,
etc.
Start or stop COLBAS tasks Dial-up communication (telephony) task
Transfer of information to various
communication partners
See "Transfer of module point
information", page 7.
Measuring points
Definition
Design
Measured value
module processing
Functions