Commissioning; General; Checks Prior To Commissioning; Communication - ABB TTH200 Operating Instruction

20 TTH200 HEAD-MOUNT TEMPERATURE TRANSMITTER | OI/TTH200-EN REV. B
... 8 Electrical connections
... Power supply
Voltage drop on the signal line
When connecting the devices, note the voltage drop on the
signal line. The minimum supply voltage on the transmitter must
not be undershot.
+
U
1
-
R
A
A Transmitter
Figure 15: HART load resistance
U : Minimum supply voltage on the transmitter
1min
U : Minimum supply voltage of the supply isolator /
2min
DCS input
R: Line resistance between transmitter and supply isolator
R : Resistance (250 Ω) for HART functionality
250
Standard application with 4 to 20 mA functionality
When connecting these components, observe the following
condition:
U ≤ U - 22 mA × R
1min 2min
Standard application with HART functionality
Adding resistance R increases the minimum supply voltage
250
U : U ≤ U - 22 mA × (R + R
2min 1min 2min
For HART functionality, use supply isolators or DCS input cards
with a HART mark. If this is not possible, a resistance of ≥ 250 Ω
(< 1100 Ω) must be added to the interconnection.
The signal line can be operated with / without grounding. When
establishing a ground connection (minus side), make sure that
only one side of the terminal is connected to the equipotential
bonding.
R
+
250
U
2
-
B
A11122
B Supply isolator / DCS input with
supply / segment coupler
)
250

9 Commissioning

General

In case of corresponding order the transmitter is ready for
operation after mounting and installation of the connections.
The parameters are set at the factory.
The connected lines must be checked for firm seating. Only
firmly seated lines ensure full functionality.

Checks prior to commissioning

The following points must be checked before commissioning the
device:
• Correct wiring in accordance with Electrical connections
on page 15.
• The ambient conditions must correspond to the
information given on the name plate and in the data
sheet.

Communication

Note
The HART® protocol is an unsecured protocol, as such the
intended application should be assessed to ensure that these
protocols are suitable before implementation.
Communication with the transmitter takes place using the HART
protocol. The communication signal is modulated onto both
wires of the signal line in accordance with the HART FSK 'Physical
Layer' specification.
The HART modem is connected at the signal line of the current
output via which power is also supplied via the power supply
unit.