VEGA VEGADIS 62 - Manual (Page 45)

10 .2 HART communication
The HART protocol operates with the technology of the frequency shift keying (FSK = frequency shift
keying) based on the data communication standard Bell 202. The digital signal is generated out of the
frequencies 1200 and 2200 Hz representing each the bit information 1 and 0. Sinus curves with these
frequencies are superimposed to the direct current in the wire pair of the field device. The average
value of the superimposed signal is zero. Hence the 4 … 20 mA signal is not influenced by the digital
data transmission.
Commands when transmitting
During transmission, only the long address format is used which is supported by all sensors as of
HART revision 5.
Command no. Command name Description
0 Read UID For determination of the UID from the HART address
1 Read primary variable For reading out the measured value
15 Read output information To update the scaling of the display after ZERO or
SPAN
34 Write damping value -
35 Write range values Adjustment of the transmitter scaling
36 Set upper range value Max. adjustment/SPAN
37 Set lower range value Min. adjustment/ZERO
44 Write PV units Adjustment of the transmitter unit
Command during reception
Only messages are received the return address of which correspond with adjusted polling address or
the determined UID.
Command no. Command name Description
1 Write polling adress HART address modified by the control room is
accepted by the display
6 Read current & 4 vars For checking the set measuring unit
15 Read output information Accept transmitter scaling
34 Write damping value Setting transmitter damping by control room
35 Write range values Transmitter scaling by control room
36 Set upper range value Max. adjustment/SPAN through control system
After receipt, the new scaling is read out with command
15
VEGADIS 62 45
10 Supplement
36469
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EN
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