II - DCE FEL ČVUT v Praze

SIMATIC S7 HART Analog Modules
4.2.2 How to Use HART
System
environment
Field device with HART functionality
4-6
HART hand-held device
To use a smart field device with HART functionality, you require the
following system environment (see Figure 4-3):
Current loop 4 - 20 mA
HART parameter assignment tool:
You can set the HART parameters either with an external hand-held
controller (HART hand-held device) or by using a HART parameter
assignment tool. The parameter assignment tool accesses the HART
analog module directly, whereas the HART hand-held device is connected
parallel to the field device. The PDM (Process Device Manager) can be
obtained as an autonomous tool (stand alone) or it can be embedded in
STEP7 HW Config. For the latter, an optional package is required.
How HART is linked to the system:
The HART analog module assumes the function of a “master,” in that it
receives the commands from the HART parameter assignment tool,
forwards them to the field device, and then sends back the responses. The
interface of the HART analog module comprises data records which are
transmitted via the I/O bus. The data records must be created and
interpreted by the HART parameter assignment tool.
Interface connection for HART parameter assignment tool:
DP Connection which is capable of master class 1 as well as master
class 2 functionality.
4...20 mA
Fig. 4-3 System environment required for HART
Error handling
HART resistance
Modem
L+: 24V
Analog to digital conversion
ADC
of the cyclic measured
value
G : Ground
HART analog module
Filtering out of
HART signal
Interface
connection to
PROFIBUS
SIMATIC
PDM
HART parameter assignment tool
The two HART status bytes transmitted with each response of the field
device contain error information relating to HART communication, HART
commands and device status, (see HART communication data records,
Section 4.8.3).
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04