Honeywell Series STT250 Temperature Transmitter Supports 4-20ma/HART/Honeywell DE Output

Product Description :

Choose the unit to meet your application needs:
• STT820: Rigid Probe assembly without thermowell

• STT830: Threaded and socket weld assembly with
thermowell and extension

• STT840: Drilled Flanged assembly with thermowell
and extension.

Range:
All engineering range parameters must be entered to match the trip points in the safety logic solver. These parameters must be verified during the installation and commissioning to ensure that the correct parameters are set in the transmitter.

Engineering range parameters can be verified by reading these parameters from the local display or by checking actual calibration of the transmitter.

Description of product :

The HONEYWELL STT25S Smart HART Temperature transmitter will report a stable PV within ( 6.0s to 7.0s ) of a power on condition. Once powered the internal update rate of the STT25S is ( 0.8s to 1.4s). The HONEYWELL STT25T6 Smart HART Temperature transmitter will report a stable PV within ( 6.0s to 8.5s ) of a power on condition.

Once powered the internal update rate of the STT25T6 is ( 1.1s to 4.5s). The power on startup times of both the STT25S and STT25T6 models are impacted by the initialization times of the CPU and its Input/Output (I/O). The steady state update rates are impacted by the amount of HART communications occurring on the communications link between the HART host and the STT25S and STT25T6 devices. The safety performance response time for updating temperature through a host system will be the device update rate for the 4 - 20mA loop plus the lag time required for the host to process the change on the analog input of the system.

The logic solver must be configured so that the engineering range within the transmitter matches the expected range of the logic solver. To take advantage of the internal diagnostics in the STT250 Smart Temperature transmitter HART models (STT25S & STT25T6), the logic solver must be configured to annunciate an out of band current reading diagnostic fault (greater than 20.8 mA. or less than 3.8 mA.) in a standard instrument or (greater than 21.0 mA. or less than 3.8 mA.) with the Namur option enabled.

Should a ‘Critical’ error be detected within the device, the device 4 – 20mA output will go to the configured burnout current, in addition to an error flag will be set to indicate to a host through HART communications. The logic solver configuration must consider the slew time of the current signal and ensure that filtering is used to prevent a false diagnostic failure annunciation.

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