Siemens SITRANS LUT400 User guide
Siemens Milltronics Process Instruments Inc.
1954 Technology Drive, P.O. Box 4225, Peterborough, ON Canada K9J 7B1
Tel: (705) 745-2431 Fax: (705) 741-0466 www.siemens-milltronics.com
Email: techpubs@siemens-milltronics.com
AG091712
SITRANS LUT400 Communications Options
Connecting the LUT400 to a control system and the available data
Objective: Summarize the data types available from the LUT 400
Seven methods to connect the LUT400 to a control system
While every effort was made to verify the following information, no warranty of accuracy or usability is expressed or implied.
Overview:
The SITRANS LUT400 comes with two ports:
a USB interface
a 4-20 mA output with HART communications
The USB interface connects a computer directly to the LUT400. The user programs the device via a web browser and also
downloads the data logs by treating the LUT400 as an external hard drive.
The HART interface presents a variety of methods for getting data out of the instrument. Listed below are seven ways to connect
the LUT400 to a control system.
1. 4-20 mA card
2. HART input card (Profibus DP connection)
3. Profibus PA gateway
4. Ethernet gateway
5. Wireless HART gateway
6. Foundation Fieldbus (FF) gateway
7. Modbus gateway
Topics:
Information types
Accuracy
Connection methods
APPLICATION GUIDE
LUT400 Communications Options
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APPLICATION GUIDE
Information from a LUT400:
The LUT400 can be configured to provide a primary variable (PV) which is one of the following measures:
Level
Space
Distance
Volume
Flow
Head
The LUT400 can also provide four dynamic variables from the same list. These variables are read from the device using
HART
universal command 3
which some HART interface cards do automatically. Other HART cards will also automatically read the
device variables using HART universal command 9. The 6 variables in the list above are the 6 device variables of the LUT400.
NOTES:
to define the dynamic variables and the required order, use HART common practice commands 50 and 51.
This chart presents other variables from the LUT400 for selected monitoring and the corresponding HART command required to
read the values.1
Variable HART Command
Daily total flow
Running (actual) total flow
Command 252: read totalizer parameters
Relay out (3)
Discrete In (2)
Command 216: read relay and DI states
Transducer temperature
Temperature sensor
Command 180: read temperature settings
Pumped hours Command 226: read relay pump
External totalizer Command 220: read external totalizer
High level alarm
Low level alarm
Command 198: read alarm parameters (transaction 1)
OCM max head
OCM max flow
OCM zero offset
OCM flow rate decimals
Command 248: read OCM flow information
Data logs can not be read through HART and are only available through the USB connection.
1For more detail on the HART commands, see lit18_sitrans_lut400.pdf available on Siemens service and support:
http://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&objID=59217416&subtype=133300
LUT400 Communications Options
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APPLICATION GUIDE
Status Information:
HART provides several different status information indicators.2
Most of these gateways give the device variable status, so that an overall health of the variable is read:
2Please see Siemens application guide
Working with HART networks
(AG012712) for more details.
LUT400 Communications Options
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APPLICATION GUIDE
HART and Accuracy
The LUT400 has a stated measurement accuracy of +/- 1 mm plus the additional 0.17% of measured range. You will get this
accuracy when using HART, the display, and the data logs. However, the 4-20 mA channel has a transmit, transmission, and
receive error in addition to the measurement error, but we do not have data on the transmission and receive errors.
The transmission error depends on the wire used, length, and amount of noise. The receive error varies from card to card and is
typically not published.
The transmit error is known for the LUT400 and is under 0.005 mA with a worst-case error of 0.02 mA. At first glance, these
numbers do not appear to be significant. However, upon calculation, it becomes apparent that this small change adds
considerably to the overall error:
Consider a three-meter, high accuracy unit.
1. Over the three-meter range, a 0.005 mA error is 0.03125 % of 16 mA (range of 4 to 20 mA).
2. Multiply this by the measurement range of three meters equals an additional 0.9375 mm error – almost the same as the
measurement error.
3. Doing a similar calculation for the worst case error of 0.02 mA, you will get a transmit error of up to 5.8 mm.
Conclusion: Using 4-20 mA can result in your value being out between 1 mm and 6.8 mm.
LUT400 Communications Options
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APPLICATION GUIDE
For a 60-meter device, a similar calculation gives a typical error of 18.8 mm and worst-case error of 75 mm.
The measurement error is +/- 1 mm plus 0.17 % of the measurement which then equals up to 11mm at 60 meters.
Conclusion: using 4-20 mA can result in your value being out between 11 mm and 86 mm.
LUT400 Communications Options
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APPLICATION GUIDE
1. 4-20 mA card
Access to Process Variable: Only via 4-20 mA
Access to Secondary Variable: No
Access to variables from HART commands: No
Access to status information: No
Full accuracy: No
PDM access: Yes, locally via HART modem
PACTware access: Yes, locally via HART modem
AMS access: Yes, locally via HART modem
Benefits: Easy to use
Disadvantages:
Do not get any status information on the health of the device
No remote access to the field device
Can only view one variable
Less accuracy
Equipment Notes: Applies to any
manufacturer’s 4-20 mA input cards. Please
note that there are different levels of
accuracy and conversion speed in 4-20 mA
cards.
LUT400 Communications Options
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APPLICATION GUIDE
2. HART input card in an ET200M
Access to Process Variable: Yes
Access to Secondary Variable: Yes
Access to variables from HART commands: Yes
Access to status information: Yes
Full accuracy: Yes
PDM access: Yes, local or remote access possible
PACTware access: Yes, local or remote access possible
AMS access: Yes, but only via remote access at this point.
Benefits:
Full connection into TIA.
Provides status information to indicate the health of the device
Full and easy access via configuration software
Full accuracy
Disadvantages: Higher cost per point.
Equipment notes: The ET200M is a remote I/O
rack on Profibus DP and is made by Siemens.
It works with any Profibus DP master. For
this application, both the ET200M module
plus a HART input module for the ET200M are
required.
LUT400 Communications Options
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APPLICATION GUIDE
3. Profibus PA Gateway
Access to Process Variable: Yes
Access to Secondary Variable: Yes
Access to variables from HART commands: No
Access to status information: Yes
Full accuracy: Yes
PDM access: Local access via HART modem
PACTware access: Local access via HART modem
Benefits:
Connection onto PA network
Access to PV and status information
Full accuracy
Disadvantages:
Higher cost than 4-20 mA
No remote access via configuration software
Equipment notes: the key piece of equipment
for this application is the T500, a Profibus PA
to HART gateway made by Fieldbus
International AS (Fint). Order directly from
Fint at www.fint.no.
LUT400 Communications Options
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APPLICATION GUIDE
LUT400 Communications Options
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APPLICATION GUIDE
4. Ethernet Gateway
Access to Process Variable: Yes
Access to Secondary Variable: Yes
Access to variables from HART commands: Yes
Access to status information: Yes
Full accuracy: Yes
PDM access: Local and remote access
PACTware access: Local and remote access
AMS access: Local access
Benefits:
Easy to use HART data concentrator
Remote access via configuration software
Easy to connect to HMI via OPC
Full accuracy.
Disadvantages:
Higher cost than 4-20 mA.
Equipment notes: The Ethernet gateway is
made by Ifak. The head module is called
isNetLite and the HART modules are isNet
H@rt4 and isNet H@rt8. They can be
purchased directly from Ifak at www.ifak-
system.com.
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