STT850 and STT750 SmartLine

Temperature Transmitter
HART® Communications Options
Safety Manual

34-TT-25-05
Revision 5
January 2020

Honeywell Process Solutions

 Copyrights, Notices and Trademarks
−
© Copyright 2020 by Honeywell, Inc.
Revision 5, January 2020
−
While the information in this document is presented in good faith and believed to be accurate,
Honeywell disclaims any implied warranties of merchantability and fitness for a particular
purpose and makes no express warranties except as may be stated in the written agreement with
and for its customers. In no event is Honeywell liable to anyone for any indirect, special, or
consequential damages. The information and specifications in this document are subject to
change without notice.

Honeywell, TDC 3000, SFC, SmartLine, PlantScape, Experion PKS, and TotalPlant are
registered trademarks of Honeywell International Inc. Other brand or product names are
trademarks of their respective owners.

Honeywell Process Solutions

1250 W Sam Houston Pkwy S
Houston, TX 77042

ii STT850 & STT750 Safety Manual January 2020

 About This Document

Release Information
STT850 and STT750 SmartLine Transmitter HART® Communications Options Safety Manual,
# 34-TT-25-05.

Revision Date of Change Details of Change

1 March 2014 1st Release (STT850 only)
2 August 2015 STT750 Temperature Transmitter added.
3 March 2016 Digital Output for STT850
4 September 2017 Failure rates info added
5 January 2020 Web links updated

References
The following list identifies publications that may contain information relevant to the information
in this document.
STT850
• STT850 SmartLine Temperature Transmitter Specifications, 34-TT-03-14
• STT850 SmartLine Temperature Transmitter Quick Start Installation Guide,
# 34-TT-25-04
• STT 850 SmartLine Temperature Transmitter User Manual, Document # 34-TT-25-03
• STT850 SmartLine Temperature Transmitter HART/DE Option User’s Manual,
# 34-TT-25-06
STT750
• STT750 SmartLine Temperature Transmitter Specification, 34-TT-03-16
• STT750 SmartLine Temperature Transmitter Quick Start Installation Guide,
# 34-TT-25-14
• STT 750 SmartLine Temperature Transmitter User Manual, Document # 34-TT-25-13
• STT750 SmartLine Temperature Transmitter HART Option User’s Manual,
# 34-TT-25-16

Patent Notice
The Honeywell STT850 SmartLine Temperature Transmitter family is covered by one or more of
the following U. S. Patents: 5,485,753; 5,811,690; 6,041,659; 6,055,633; 7,786,878; 8,073,098;
and other patents pending.

January 2020 STT850 & STT750 Safety Manual iii

Support and Contact Information
For Europe, Asia Pacific, North and South America contact details, refer to the back page of this
manual or the appropriate Honeywell Solution Support web site:

Honeywell Corporate www.honeywellprocess.com

Honeywell Process Solutions www.honeywellprocess.com/temperature-transmitters/
Training Classes http://www.honeywellprocess.com/en-US/training

Telephone and Email Contacts

Area Organization Phone Number
United States and 1-800-343-0228 Customer Service
Honeywell Inc.
Canada 1-800-423-9883 Global Technical Support
Global Email Support Honeywell Process Solutions ask-ssc@honeywell.com

iv STT850 & STT750 Safety Manual January 2020

Terms and Abbreviations
1oo1 One out of one
Basic Safety The equipment must be designed and manufactured such that it protects
against risk of damage to persons by electrical shock and other hazards
and against resulting fire and explosion. The protection must be effective
under all conditions of the nominal operation and under single fault
condition
DU Dangerous Undetected failures
FMEDA Failure Modes, Effects and Diagnostic Analysis
Functional The ability of a system to carry out the actions necessary to achieve or
Safety to maintain a defined safe state for the equipment / machinery / plant /
apparatus under control of the system
GTS Global Technical Support Center
HART® Highway Addressable Remote Transducer
HFT Hardware Fault Tolerance
Low demand Mode, where the frequency of demands for operation made on a safety-
mode related system is no greater than one per year and no greater than twice
the proof test frequency.
PFDAVG Average Probability of Failure on Demand
Safety Freedom from unacceptable risk of harm
Safety The investigation to arrive at a judgment - based on evidence - of the
Assessment safety achieved by safety-related systems. Further definitions of terms
used for safety techniques and measures and the description of safety
related systems are given in IEC 61508-4.
SFF Safe Failure Fraction, the fraction of the overall failure rate of a device
that results in either a safe fault or a diagnosed unsafe fault.
SIF Safety Instrumented Function, a set of equipment intended to reduce the
risk due to a specific hazard (a safety loop).
SIL Safety Integrity Level, discrete level (one out of a possible four) for
specifying the safety integrity requirements of the safety functions to be
allocated to the E/E/PE safety-related systems where Safety Integrity
Level 4 has the highest level of safety integrity and Safety Integrity Level
1 has the lowest.
SIS Safety Instrumented System – Implementation of one or more Safety
Instrumented Functions. A SIS is composed of any combination of
sensor(s), logic solver(s), and final element(s).

January 2020 STT850 & STT750 Safety Manual v

 Contents
Terms and Abbreviations ................................................................................................................. v

1 — Requirements ..................................................................................................... 1
Requirements for use of the manual ................................................................................................... 1

2 — Safety Function ................................................................................................... 2

Primary Safety Functions .................................................................................................................... 2
Secondary Safety Functions ............................................................................................................... 2
Systematic Integrity: SIL 3 Capable .................................................................................................... 2

3 — Designing with the HONEYWELL STT850 & STT750 ........................................ 3

Diagnostic Response Time ................................................................................................................. 3
Logic Solver Inputs .............................................................................................................................. 3
Reliability data and lifetime limit .......................................................................................................... 3
Environmental limits ............................................................................................................................ 4
Application limits .................................................................................................................................. 4

4 — Installation with the HONEYWELL STT850 & STT750 ....................................... 5

Parameter settings .............................................................................................................................. 5

5 — Operation and Maintenance with the HONEYWELL STT850 & STT750 ........... 6
Proof test ............................................................................................................................................. 6
Calibration procedure .......................................................................................................................... 7
Remote Parameter Configuration Verification ..................................................................................... 8
Repair and replacement ...................................................................................................................... 9
Firmware update .................................................................................................................................. 9

vi STT850 & STT750 Safety Manual January 2020

 1 — Requirements
Requirements for use of the manual
This section is intended for user’s who have our STT850 & STT750 SmartLine Temperature
Transmitter with the HART® Communication option with SIL. Any other option is not
specifically covered by this manual.

IEC 61508 Ed. 2.0 compliant hardware/software revisions for the STT850 & STT750 SmartLine
Temperature Transmitter can be found in the Exida and TÜV Certification Reports.

In addition, the most recent release information can be found in the following document:
https://www.honeywellprocess.com/library/support/Public/Documents/SmartLineHARTTemperatureF
irmwareRevisions.zip

This document can be downloaded using the following link:

https://www.honeywellprocess.com/SmartLineHARTTemperatureFirmwareRevisions.zip

January 2020 STT850 & STT750 Safety Manual 1

 2 — Safety Function
Primary Safety Functions
The HONEYWELL STT850 & STT750 measures the temperature (or mV, Volts or ohms) of a
process and reports the measurement within a safety accuracy of 2%.

Secondary Safety Functions

The HONEYWELL STT850 & STT750 performs automatic diagnostics to detect internal failures
and reports these failures via out of band signals on the 4 – 20 mA output.
The transmitter needs a power cycle in order to recover from this condition.

If the Digital Output (STT850 only) is configured for "Critical Diagnostic" then it will turn on
when the automatic diagnostics detect an internal failure.

Systematic Integrity: SIL 3 Capable

SIL 3 Capability:

The product has met manufacturer design process requirements of Safety Integrity Level (SIL) 3.
These are intended to achieve sufficient integrity against systematic errors of design by the
manufacturer. A Safety Instrumented Function (SIF) designed with this product must not be used
at a SIL level higher than the statement without “prior use” justification by end user or diverse
technology redundancy in the design. This is a Type B device.

2 STT850 & STT750 Safety Manual January 2020

 3 — Designing with the HONEYWELL STT850 & STT750
Diagnostic Response Time
The HONEYWELL STT850 & STT750 will report an internal failure within 12 minutes of fault
occurrence (worst case).
The transmitter will be put to burnout output if
1. PV is not updated in 5 seconds
2. 4-20mA Output Current is not as expected in 2.5 minutes
3. Electronics fault is found in 12 minutes (worst case).
4. If the Digital Output (STT850 only) is configured for "Critical Diagnostic" then it will
turn on at these same times
The transmitter needs to be power cycled in order to recover from the burnout condition.

Logic Solver Inputs

The logic solver must be configured so that the engineering range in the transmitter matches the
expected range of the logic solver.
To take advantage of the internal diagnostics in the STT850 & STT750, the logic solver must be
configured to annunciate an out of band current reading (greater than 20.8 mA. or less than 3.8
mA.) in standard configuration or (greater than 20.5 mA. or less than 3.8 mA.) with Namur
configuration as a diagnostic fault. 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.
If the Digital Output (STT850 only) is used for a Logic Solver application, then the transmitter
must be configured to use only the High Burnout mode as the Digital Output is shut off when the
transmitter is in Low Burnout."

Reliability data and lifetime limit

A detailed Failure Mode, Effects, and Diagnostics Analysis (FMEDA) report is available from
HONEYWELL. This report details all failure rates and failure modes, common cause factors for
applications with redundant devices and the expected lifetime of the HONEYWELL STT850 &
STT750 AND STT750.
The HONEYWELL STT850 & STT750 is intended for low demand mode applications up to SIL
2 for use in a simplex (1oo1) configuration, depending on the PFDAVG calculation of the entire
Safety Instrumented Function. STT850 & STT750 is classified as type B device according to
IEC61508, having a hardware fault tolerance of 0.
The development process of the HONEYWELL STT850 & STT750 is certified up to SIL3,
allowing redundant use of the transmitter up to this Safety Integrity Level, depending the PFDAVG
calculation of the entire Safety Instrumented Function.
When using the HONEYWELL STT850 & STT750 in a redundant configuration, a common
cause factor should be included in reliability calculations. For reliability calculation details, useful
lifetime and SFF, see the FMEDA report.
The reliability data listed the FMEDA report is only valid for the useful life time of the
HONEYWELL STT850 & STT750. The failure rates of the HONEYWELL STT850 & STT750
may increase sometime after this period. Reliability calculations based on the data listed in the
FMEDA report for mission times beyond the lifetime may yield results that are too optimistic, i.e.
the calculated Safety Integrity Level will not be achieved.
Failure rates of the T/C, RTD, and E/U meter must be added and considered in the overall failure
rate for the STT850 & STT750.

January 2020 STT850 & STT750 Safety Manual 3

Environmental limits
The environmental limits of the HONEYWELL STT850 & STT750 are specified in the customer
spec sheets as given in the STT850 & STT750 Specification 34-TT-03-14.

Application limits
The application limits of the HONEYWELL STT850 & STT750 are specified in the User
Manual. If the transmitter is used outside of the application limits the reliability data provided
becomes invalid.

4 STT850 & STT750 Safety Manual January 2020

 4 — Installation with the HONEYWELL STT850 & STT750
The person with knowledge of safety operations will be required to do the installation and
operation. No special installation is required in addition to the standard installation practices
outlined in the STT850 & STT750 Smart Transmitter User Manual. However please note that
when the device is in safety operation the optional write protect must be set in hardware and
software both so that the device is write protected and HART® devices must be disconnected.
This can be done using the write protect jumper. See STT850 & STT750 Smart Transmitter User
Manuals for details concerning the write protect jumper (STT850 – 34-TT-25-03,
STT750 – 34-TT-25-13). Also note that when the device is in safety operation the Latching and
Break Detect parameters must be enabled.
If the Digital Output (STT850 only) function is being used in a Safety Application then it too
should be set for Latching. Also, as the Digital Output is disabled when the transmitter is in the
Low-burnout mode, then when using a Digital Output in a Safety Application the transmitter
should only be configured to use High-burnout mode. See STT850 & STT750 Smart Transmitter
User Manuals for details concerning these parameters

The software write protect is also available in the device with a password to disable the software
write protect. The default password is “0000”. It can be enabled / disabled through HART host.
IEC 61508 Ed. 2.0 compliant hardware/software revisions for the STT850 & STT750 can be
found in the Exida and TÜV Certification Reports. In addition, the most recent release
information can be found in the following document:
https://www.honeywellprocess.com/library/support/Public/Documents/SmartLineHARTTemperatureF
irmwareRevisions.zip

Parameter settings
The following parameters need to be set in order to maintain the designed safety integrity:

mA Fault action The transmitter is shipped with a default failsafe

(Upscale/Downscale) direction of upscale (21.5 mA.). This is acceptable
for all high trip applications. For low trip
applications, the fail-safe direction is downscale (3.5
mA.). A jumper on the transmitter may be changed
to accomplish this action, see the User Manual.

Engineering 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.

January 2020 STT850 & STT750 Safety Manual 5

 5 — Operation and Maintenance with the
HONEYWELL STT850 & STT750
Proof test
The objective of proof testing is to detect failures within the HONEYWELL STT850 & STT750
that are not detected by the automatic diagnostics of the transmitter. Of main concern are
undetected failures that prevent the safety instrumented function from performing its intended
function.
The frequency of proof testing, or the proof test interval, is to be determined in reliability
calculations for the safety instrumented functions for which the HONEYWELL STT850 &
STT750 is applied. The Exida exSILentia® tool is recommended for these calculations. The
proof tests must be performed more frequently than, or as frequently as specified in the
calculation in order to maintain the required safety integrity of the safety instrumented function.
The following proof test is recommended. It consists of a simple HART® driven min to max
output test. The results of the proof test need to be documented and this documentation should be
part of a plant safety management system. Any failures that are detected and that compromise
functional safety should be reported to the Global Technical Support Center (GTS).
See STT850 & STT750 Smart Transmitter User Manual for more details (STT850 – 34-TT-25-
03, STT750 – 34-TT-25-13).

Step Action

1 Bypass the safety PLC or take other appropriate action to avoid a false trip, following
Management of Change procedures.
2 Send a HART® command to the transmitter to go to the high alarm current output and verify that
the analog current reaches that value.
This procedure tests for compliance voltage problems such as a low loop power supply voltage
or increased wiring resistance. This also tests for other possible failures.
3 Send a HART® command to the transmitter to go to the low alarm current output and verify that
the analog current reaches that value. This test checks for possible quiescent current related
failures.
4 Use the HART® communicator to view detailed critical and non-critical device status to ensure
no alarms or warnings are present in the transmitter.
5 Verify all safety critical configuration parameters.
6 The WP jumper state should be checked to see if it is in WP mode first, and then changed to
Enable to ensure a change is detected by device while configuring, and then moved back to WP
after the configuration is complete. Then it should be verified again.
7 Calibrate the device as per calibration procedure given below.
8 Restore the loop to full operation.
9 Power cycle or cold reset to clear soft errors in memory (RAM).
10 Remove the bypass from the safety PLC or otherwise restore normal operation.
11 If Digital Output (DO) is present, change the monitored input such that the DO turns on and off.
Monitor the output to confirm that the DO works as expected.

6 STT850 & STT750 Safety Manual January 2020

 This test will detect approximately 30% of possible DU failures in the transmitter (Proof Test
Coverage). An alternative proof test consisting of proof test 1 with actual two point temperature
calibration plus verification of the temperature measurement will detect approximately 48% of
possible DU failures.
The person(s) performing the proof test of the HONEYWELL STT850 & STT750 should be
trained in SIS operations, including transmitter maintenance and company Management of
Change procedures. Tools required are: handheld communicator.

Calibration procedure
The transmitter should be taken out of service. The source for the input Temperature must be very
precise, and certified for correct operation.

Step Action

1 Connect the HART host and establish the communications.

2 Go to Online > Device Setup > Calibration > Calibration Methods menu.
3 Go to “D/A Trim”
4 Message “Warn loop should be removed from automatic control” will appear. Press “Ok”.
5 Message “Connect reference meter” will appear. Connect the reference meter and press “Ok”.
6 Message “Setting fld device output to 4mA” will appear. Press “Ok”. Message “Enter meter value
(4,000mA)” will appear with a textbox to enter actual value observed on meter. Enter the actual
value and press “Enter”.
7 Message “Fld dev output 4,000mA equal to reference meter?” will appear with Yes/No selection.
Select “Yes” and “Enter”.
8 Message “Setting field device output to 20mA” will appear. Press “Ok”.
9 Message “Fld dev output 20,000mA equal to reference meter?” will appear with Yes/No selection.
Select “Yes” and “Enter”.
10 Message “Returning fld dev to original output” will appear. Press “Ok”.
11 Now Double click “URV Correct” method
12 Message “WARN-Loop should be removed from automatic control” will appear. Press “Ok”.
13 . Message “Please enter calibration date” will appear. Enter the current date and press “Ok”.

14 Message “Please enter current calibration time in 24 hr clock format (hour field)” will appear.
Enter the current time hour and press “Ok”.
15 Message “please enter current calibration time (min field)” will appear. Enter the current time
minutes and press “Ok”.
16 Message “Apply URV Temperature” will appear.
17 Adjust the PV input to the required URV value. Press “Ok”.
18 Message “Press ok when Temperature is stable” will appear. Press “Ok”
19 The correct URV operation will happen .
20 Message “Loop may be returned to automatic control” will appear. Press “Ok”.
21 Follow the same procedure for “Correct LRV” (replace URV in above procedure by LRV) and
“Correct LRV” operation will get executed.

January 2020 STT850 & STT750 Safety Manual 7

Remote Parameter Configuration Verification
When configuring the HONEYWELL STT850 & STT750 through a remote host, it is
recommended that parameters that affect the 4-20ma analog output be verified using an alternate
utility, before using the transmitter in a SIS. This helps to ensure that the parameters that are
entered remotely by the host are not inadvertently changed from the user intended values.

The procedure can consist of listing the parameters and their values entered in the host
application. Then, using an alternative application, the same parameters are read back and noted
in the same form. The form is then signed, dated, and filed for future reference. See Table 1 -
Example Verification Form for an example of this form.

Note that using the same host application to verify the remotely entered values will not provide as
much assurance as using an alternate application.

Table 1 - Example Verification Form

Parameter Host Value Verified Value

Verified By:
Date:

8 STT850 & STT750 Safety Manual January 2020

Repair and replacement
Any failures that are detected and that compromise functional safety should be reported to the
Global Technical Support Center (GTS).
When replacing the HONEYWELL STT850 & STT750 the procedures in the installation manual
should be followed.

Firmware update
The user will not be required to perform any firmware updates. If the user has selected the
firmware upgrade option, it can be done by Honeywell service representative.

January 2020 STT850 & STT750 Safety Manual 9

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10 STT850 & STT750 Safety Manual January 2020

Sales and Service
For application assistance, current specifications, pricing, or name of the nearest Authorized Distributor, contact one
of the offices below.

ASIA PACIFIC EMEA AMERICAS

Honeywell Process Solutions, Honeywell Process Solutions, Honeywell Process Solutions,
(TAC) hfs-tac-support@honeywell.com Phone: + 80012026455 or Phone: (TAC) 1-800-423-9883 or
+44 (0)1344 656000 215/641-3610
Australia (Sales) 1-800-343-0228
Honeywell Limited Email: (Sales)
Phone: +(61) 7-3846 1255 FP-Sales-Apps@Honeywell.com Email: (Sales)
FAX: +(61) 7-3840 6481
Toll Free 1300-36-39-36 or FP-Sales-Apps@Honeywell.com
Toll Free Fax: (TAC) or
1300-36-04-70 hfs-tac-support@honeywell.com (TAC)
hfs-tac-support@honeywell.com
China – PRC - Shanghai
Honeywell China Inc.
Phone: (86-21) 5257-4568
Fax: (86-21) 6237-2826

Singapore
Honeywell Pte Ltd.
Phone: +(65) 6580 3278
Fax: +(65) 6445-3033

South Korea
Honeywell Korea Co Ltd
Phone: +(822) 799 6114
Fax: +(822) 792 9015

For more information

To learn more about SmartLine Transmitters,
visit www.honeywellprocess.com
Or contact your Honeywell Account Manager

Process Solutions
Honeywell
1250 W Sam Houston Pkwy S
Houston, TX 77042

Honeywell Control Systems Ltd

Honeywell House, Skimped Hill Lane
Bracknell, England, RG12 1EB

Shanghai City Centre, 100 Jungi Road

Shanghai, China 20061
34-ST-25-05, Rev.5
January 2020
www.honeywellprocess.com 2020 Honeywell International Inc.