Acyclic Communication - Siemens SITRANS F Operating Instructions Manual

Commissioning
6.5 Configuring with PROFIBUS PA
Cyclic communication
The master can cyclically read out the "OUT" measured value from the MEM-PPA
transmitter. The measured value is represented as a 32-bit floating-point number in
accordance with IEEE-754; the corresponding status is represented as an 8-bit word. The
unit of the measured value can be selected (see Acyclic communication/unit of measured
value).
Assigning a meaning to the status word
The meaning of the status messages has been defined by the PROFIBUS User Organization
(PNO).
The device reports the following states:
Hex
0x8A
0x89
0x8E
0x8D
0x52
0x51
6.5.2

Acyclic communication

Parameters of the Transducer Block
Set Zero
The zero point can be changed manually. The zero point parameter is set in the unit of
flow/level/density and is continuously subtracted from the uncorrected measured value.
Calibration factor
The measured value is multiplied by the calibration factor. This factor is 1 when the device is
shipped from the factory. The following formula is used:
Flow rate = (uncorr. flow rate – zero point) ▪ calibration factor
Low-flow cutoff
The unit of the low-flow cutoff is identical to the unit of the flow rate. At level/density
applications this parameter should be set to zero. If the flow drops below the low-flow cutoff,
the measured value will be set to zero. Hysteresis is 3%, with an unilateral effect.
42
Meaning Quality of the
measuring value
Exceeding Good
HI-LIM
Shortfalling LO-LIM Good
Exceeding Good
HI-HI-LIM
Shortfalling Good
LO-LO-LIM
Exceeding upper Uncertain, measured
value is inaccurate
Falling below lower Uncertain, measured
value is inaccurate
Condition
Measured value exceeding warning value
Measured value is falling below warning value
Measured value exceeding alarm value
Measured value falling below alarm value.
Sensor limit exceeding limit value
Sensor limit falling below limit value
Operating Instructions, 02/2013, A5E03821131-01
SITRANS FVA250