Design And Function; Input Functionality; Sensor Redundancy - ABB TTF300 Operating Instruction

22 TTF300 FIELD-MOUNT TEMPERATURE TRANSMITTER | OI/TTF300-EN REV. I

4 Design and function

TTF300 digital transmitters are communication-ready devices
with microprocessor-controlled electronics.
In the HART® transmitter, an FSK signal is superimposed on the
4 to 20 mA output signal in accordance with the HART standard
to facilitate bidirectional communication.
With PROFIBUS PA transmitters, communication takes place in
accordance with PROFIBUS – MBP (IEC 61158-2), PROFIBUS PA
Profile 3.01.
With FOUNDATION Fieldbus® transmitters, communication
takes place in accordance with the FOUNDATION Fieldbus H1
(IEC 61158-2), ITK Version 5.x.
The transmitters can be configured using various tools / drivers.
Status and measured values can also be queried. These include
DTM, EDD and FDI Packages of the Field Information Manager
(FIM).
These tools provide an event monitor and a configuration
monitor for HART devices from SW-Rev.: 03.00.
This allows critical events such as exceeding or falling below
specified limit values and configuration changes to be output
and logged. See the HART interface description
(COM/TTX300/HART).
As an option, the transmitter can be fitted with an LCD-indicator
type B. It also supports configuration of the device using the
operating buttons.
1 Supply voltage cable
2 TTF300 transmitter
3 Temperature sensor
Figure 11: Design
4 Thermowell
5 Sensor connection cable

Input functionality

Sensor redundancy

To enhance system availability, the TTF300 has two sensor
inputs.
The second sensor input can be used redundantly for both
resistance thermometers (2 × three-wire circuit or 2 × two-wire
circuit) and thermocouples or a combination of both. If a
combination of both is used, the resistance sensor must be
connected to channel 1 and the thermocouple to channel 2, see
Electrical connections on page 29.
In the case of HART devices, the failure of a sensor can be
signaled with a configurable analog alarm pulse, see the HART®
"COM/TTX300/HART" interface description.
Devices with PROFIBUS PA®, FOUNDATION Fieldbus®, and
HART® to SW-Rev.: 01.03
Sensor redundancy / sensor backup for enhanced availability
With sensor redundancy (sensor backup), the temperature is
always measured between both sensors, and the mean is derived
from that with the same sensors.This value is provided at the
output of the transmitter.If the sensors are not identical, the
measured value of channel 1 (resistance thermometer) is
output.If one sensor fails, the temperature measurement of the
remaining sensor is transmitted seamlessly to the output of the
transmitter.
A relevant diagnosis message is available via DTM, EDD, FDI
Package (FIM) or on the LCD indicator.The measured value
remains available and maintenance measures can be taken at the
same time.
Devices with HART® from SW-Rev. 03.00
Extended configuration options are available for redundant
operation.
Redundancy behavior can be configured for:
• increased availability (standard factory setting with
redundancy),
• increased safety and
• increased accuracy (output of the average value).