Measured Value Status - Siemens SITRANS P300 Operating Instructions Manual

Operating functions via HART
7.4 Selecting the measurement type
Figure 7-5
DV [x]
p
In the example, the two pairs of values 0%;0% and 100%;100% are configured for the
customized characteristic curve. Any curve forms can be calculated here using 30 vertices
and then stored in the device via SIMATIC PDM or the HART Communicator. In the
calculation example, the value at the characteristic curve input point is transferred 1:1 to the
output point.
A number of filled vessels has to be set for the output scaling. You can enter five
characters/digits here for any given unit. Do not confuse this with the user-programmable
display unit of the "Analog output" block. With a zero point of 0 vessels and a limit point of
1000 vessels, a value of 250 vessels is yielded in the example for the "User" device variable
at a process pressure of 0.5.
See also
Measured value status (Page 7-10)
Analog output block (Page 7-13)
7.4.8

Measured value status

Introduction
Every device variable is assigned a status byte, to indicate the quality of the measured
values. This status byte can take on the states BAD, GOOD, MANUAL, UNCERTAIN. The
identifiers CONSTANT, HIGH LIMIT or LOW LIMIT are possible as well. A higher-level
diagnosis program can display and analyze these states.
Description
During smooth, uninterrupted operation, the measured value status of all active device
variables is in the state GOOD. All inactive device variables are in the state
CONSTANT/BAD. If a pressure value exceeds or falls below the sensor limits of the device
by more than 20%, the corresponding measured value and the variables inferred from it are
UNCERTAIN. A measured value becomes BAD, on the other hand, when a variable with
status BAD was the initial value for the calculation. The basic measured values for pressure
and the temperatures become BAD if e.g. the analog-to-digital converter is not working or
7-10
Functions of the user block
Device variable x
Pressure
MA Zero value
ME Limit value
SITRANS P300 with HART communication
Operating Instructions, 06/2005, A5E00359579-02