Sensor Drift Monitoring - ABB TTH300 Operating Instruction

Design and function
3.1.2

Sensor drift monitoring

When two sensors are connected, sensor drift monitoring can be activated via the EDD or DTM.
It can be activated for the following two sensor types:
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To activate sensor drift monitoring, the transmitter must first be configured for the sensor types
referred to above. Following this, the maximum permissible sensor deviation must be
configured, e.g., max. 1 K.
Since sensor response times may be marginally different, it is then necessary to set a limit time
period during which the sensor deviation must be continuously larger than the maximum sensor
drift differential value defined previously (1°K, for example).
If the transmitter records a larger sensor deviation during the defined time period, a HART,
EDD, and DTM diagnostic notification - "Maintenance required" - is generated according to
NE 107. At the same time, diagnostic information is shown on the LC display.
If drift monitoring is used for equivalent sensors (2x Pt100 or 2x thermocouples), the mean
value calculated from the two sensors is mapped to the transmitter's output signal as a process
variable in redundancy mode.
If a thermocouple is used for Pt100 drift monitoring, the Pt100 sensor (see Chapter 5, "Electrical
connections") must be connected to channel 1 and the thermocouple to channel 2.
The reading from channel 1 (Pt100) is mapped to the transmitter output as a process variable.
Note
Before configuring the maximum permissible sensor deviation for drift monitoring, sensor
adjustment with respect to the sensor channel 1 value must be carried out with the help of the
TTH300 DTM.
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2x resistance thermometers (RTD), two-wire circuit
2x resistance thermometers (RTD), three-wire circuit
2x resistors (potentiometers), two-wire circuit
2x resistors (potentiometers), three-wire circuit
2x thermocouples
2x voltages
1x resistance thermometer (RTD), two-wire circuit and 1x thermocouple
1x resistance thermometer (RTD), three-wire circuit and 1x thermocouple
1x resistance thermometer (RTD), four-wire circuit and 1x thermocouple
TTH300 OI/TTH300-EN