TTH300 HEAD-MOUNT TEMPERATURE TRANSMITTER | OI/TTH300-EN REV. E 27
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.
A Transmitter B Supply isolator / DCS input with
supply / segment coupler
Figure 18: HART load resistance
U
1min
: Minimum supply voltage on the transmitter
U
2min
: Minimum supply voltage of the supply isolator /
DCS input
R: Line resistance between transmitter and supply isolator
R
250
: Resistance (250 Ω) for HART functionality
Standard application with 4 to 20 mA functionality
When connecting these components, observe the following
condition:
U
1min
≤ U
2min
- 22 mA x R
Standard application with HART functionality
Adding resistance R
250
increases the minimum supply voltage
U
2min
: U
1min
≤ U
2min
- 22 mA × (R + R
250
)
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.
Unless the profile HART protocol Rev. 7 is specifically selected
during the ordering process, the device normally supports the
profile HART protocol Rev. 5 in the delivery status. The user can
later change at any time to the HART Protocol Rev. 7 profile via a
miniature switch. For additional information, see Hardware
settings on page 31.
Power supply – PROFIBUS / FOUNDATION Fieldbus
Input terminal voltage
Non-Ex application:
U
S
= 9 to 32 V DC
Ex-applications with:
U
S
= 9 to 17 V DC (FISCO)
U
S
= 9 to 24 V DC (Fieldbus Entity model I.S.)
Current consumption:
≤ 12 mA
Standard application with PROFIBUS PA and FOUNDATION
Fieldbus H1 functionality
During hookup, the following condition should be complied with:
U
1min
≤ U
2min
− 12 mA x R
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