Design And Function; Input Functionality; Sensor Redundancy - ABB TTH300 Operating Instruction

3

Design and function

Digital
electronics. They conform to the requirements of housing ingress protection type IP 20 and are
suitable for integration into DIN A and DIN B sensor heads.
With HART transmitters, for bidirectional communication purposes an FSK signal is
superimposed on the 4 ... 20 mA output signal in accordance with the HART standard.
With PROFIBUS PA transmitters, communication takes place in accordance with PROFIBUS
MBP (IEC 61158-2), PROFIBUS PA profile 3.01.
With FF transmitters, communication takes place in accordance with FOUNDATION Fieldbus
H1 (IEC 611582), ITK Version 5.1.
The transmitters can be configured, polled, and tested using a DTM or an EDD.
As an option, the transmitter can be fitted with an A or AS-type LC display. Type AS is used
exclusively for visualizing current process values.
Type A also supports the option of configuring the transmitter. It is recommended that you use
this combination.
The electrical connection between the LC display and transmitter is provided by a 6-pin flat
ribbon cable with a plug connector. The LC display can only be operated when connected to
transmitters that have an LC display interface.
3.1

Input functionality

3.1.1

Sensor redundancy

To enhance system availability, the TTH300 has two sensor inputs.
The second sensor input can be used redundantly for both resistance thermometers (2x three-
wire circuit or 2x two-wire circuit) and thermocouples, or for a mixture of these. Sensor
redundancy (or sensor backup) always involves measuring the temperature of the two sensors
and calculating the mean value on the basis of this. This value is provided at the output of the
transmitter. Should a sensor fail, the temperature measurement for the sensor that remains in
operation is provided at the output of the transmitter.
A relevant diagnostic message is provided via the EDD or DTM, or shown on the display. The
reading continues to be available and maintenance measures can be taken at the same time.
OI/TTH300-EN
transmitters are communication-ready devices
TTH300
Design and function
with microprocessor-controlled
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