Siemens Comprehensive Guide to Process Instrumentation and Analytics

© Siemens AG 2011

Monitoring and diagnostics for process instrumentation and process analytics

Standardized and meaningful diagnostics alarms are a part of the electrical device description (EDD). SIMATIC PCS 7 utilizes the EDD and forwards the relevant message automatically to the Maintenance Station. The user recei- ves information not only about which problem is involved but also on how to resolve it.

The PROFIBUS profile specification 3.01 supplies an upgrade of the status byte, now designated "Condensed Status". The purpose of the "Condensed Status" is to reduce the number of alarms and make them more user-friendly. In addition, users have the opportunity of changing the priority level for each di- agnostic alarm and thus define what is relevant to their own process.

Numerous EDDs are currently being upgraded to Enhanced EDDs. They have the following advantages:

•New standardized "look & feel" for all Siemens devices

•Quick start wizards for faster commissioning

•Improved representation of graphics for advanced diag- nostic functions

All of these functions help to reduce the maintenance costs by accelerating the diagnostic process.

When using PROFIBUS, Asset Management functions can be used to greatest effect if the devices used conform to the PROFIBUS "Identification and Maintenance" specification as well as profile specification Version 3.01. Siemens devices conform to these standards and the following information is made available:

•Manufacturer

•Order numbers

•Description

•Installation date

•Serial number

•Hardware and software modifications

This information is read directly from the measuring instru- ment and stored in the SIMATIC PDM. Here, the data can easily be recalled.

Temperature measurement

SITRANS T are the temperature measuring instruments for process engineering plants. They support commissioning and maintenance in an optimum manner and can be used in diffe- rent designs, such as complete measuring point, head-moun- ted transmitter, DIN rail mounted or distributed device.For preventive maintenance, for example, the following functions are available:

•Universal connection of resistance thermometers, thermoele- ments, resistance-type transmitters and DC voltage signals

•Monitoring of the measuring point for short circuit and open circuit

•Min/max pointer for monitoring the electronics and sensor temperature

The following devices are available as head-mounted trans- mitters or integrated into a complete measuring point:

SITRANS TH300 – the HART device

The operating hours counter evaluates the temperature valu- es of the sensor and electronics, edits them and displays them in eight temperature classes. The measured values can be ar- chived. The sensor temperature can indicate aging processes and can be used for anticipatory maintenance. The output current is monitored cyclically, simulated as a fixed value or ramp function:

•Memory function of RAM, ROM, EPROM according to checksum method

•Program sequence due to targeted approach to check- points (watchdog)

SITRANS TH400 for PROFIBUS PA

Possibility of connecting two sensors in redundant mode. The profile 3.0 device ensures easy interchangeability. With FISCO certification, use in potentially explosive areas is uncomplica- ted.

SITRANS TW for rail mounting

For installation on mounting rail with integrated power sup- ply, SITRANS TW is a universal 4-wire temperature transmitter for mounting in control cabinets:

•Monitoring of limit values and output via HART or signaling relay

•Runtime meter for electronics

SITRANS TH400 SITRANS TW

16Monitoring and diagnostics