This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Aplicaciones para transmisores de temperatura

Precise, reliable and also flexible

Applications for temperature transmitters

Hubert Jakob
ProductManager of Alexander Wiegand GmbH, Klingenberg, Germany29/11/2007

The temperature is one of the most measured parameters in industrial facilities and more than 50 percent of all the installed sensors record the temperature. Why users need sensors appropriate depending on the application. A transmitter of temperature with food, along with a measurement sensor, for example located in the head of the measuring site used to capture and amplification of the signal.

The requirements of the users to the extent of the temperature and above all the transmitters are marked by technological characteristics of the measurement and the electromagnetic influences. In addition there are other factors as the functional safety (e.g. errors signaling) which are becoming increasingly more important. In general can be summarized the needs in the following way:

• Easy to use in the Assembly.

• Easy and assisted with the task of measuring adaptation.

• Good stability of all functions, particularly in difficult environments.

• Long service life.

• Storage and simple logistics

• Economic provisioning and from the point of view of the total cost of ownership during implementation.

There are also other needs as the unequivocal signal in case of error, the functional safety (SIL), applications of security as well as antiexplosiva protection (ATEX or national type-approval). All these requirements, which are sometimes contradictory, requires extensive experience acquired in various areas of application in practice. Moreover the multiple demands as long durability and long stability constitute a synthesis of experiences both designers and users and the know-how of the manufacturer of the transmitters.

However it is clear that different applications require different solutions.

Transmitters analógicos…

This type of transmitter is of simple construction and have possibility of configuration through bridges of welding. They are very cheap with immediate delivery and form the basis of temperature transmitters.

Versions of head or lane as this integrated signaling on the sensor error. Basic construction functional safety is not very wide and the configuration possibilities are limited. Between input signal and output there Galvanic isolation, which has no effect on the accuracy of the transmitter but not isolated sensors connection must be ruled out.

... with digital setting

These analog transmitters stand out above all by its quick reaction time that electronics consists only of similar components. They are still easily configurable through software and you do without a complex simulation. This transmitter combines the advantages of digital settings with the analog signaling and as such is a suitable solution for multiplex systems implementation. Optimal conditions for storage and easy to use especially if used in large quantities.

Different approvals for EX zones with specific approvals these types of transmitters met the needs of global markets. Transmitters of such control breaks or short circuits of connected sensors.

Digital transmitters

These models stand out for its easy adaptability to various measurement tasks. They are applicable to all sensors temperature (e.g. RTD/termoelementos) or potentiometers and signals Millivolt through different connections (for example sensors of resistenca with 2-/ 3-/ 4 - threads). Smart transmitters also allow the modification with termorresistencias thermocouples and thermocouple to a Platinum.

Also apply signalling curves determined by the client.

Also in these sensors dispensed of complex simulations later configuration. The transmitter controls the sensor connected to break, short circuit and other signs of error.

The signaling of error are configurable using software to the specified applications. Signal and output constraints already correspond to the recommendations of Namur. The Protocol of the manufacturer, however, which is necessary for exchange between Software and transmitter is only configurable using the specific software from the manufacturer.

... with open protocols

A transmitter with standardized protocol (e.g. Hart) usually meet all the requirements, both General and specific.

They are easily adaptable to the tasks of measurement, the configuration to all types of sensors (RTD, thermocouple, Platinum, mV, sensor signal with específicaciones of the client)

without complex simulation of the sensor. Accurate signage are feasible without problem through specific configuration software.

With these transmitters can also be set through configuration such as e.g. AMS (Asset Management System, Emerson) "open" tools or Simatic PDM (Siemens) these configuration tools are suitable for several manufacturers and are used for the operation, adjustmentthe maintenance and diagnosis of intelligent field instruments. Of course are fulfilled Namur recommendations as the demanding requirements in reference to the antiexplosiva protection.

Another feature of this type of transmitter is the realization of global aspects of security as the SIL (Safety Integrity Level) classification which is based on a thorough analysis of FMEDA (Failure Mode and Detection analysis).

Transmitter with Foundation Fieldbus and Profibus

Digital transmitter (0... 20 mA) with Protocol

standardized open (Hart)

Transmitters Fielbus

These "intelligent" transmitters have a digital signage (according to fieldbus Protocol).

A configuration of span of measurement is not required for these models. It is sufficient for adaptation to the task of measuring the selection of the sensor (RTD, thermocouple, Platinum, specified sensor of the customer etc.) without simulation of the sensor. A detailed signage (error and State) through the digital signal is broadcast. These models are also available with antiexplosiva protection.

However there are still no classifications SIL or FMEDA reports.

The measure of temperature is a somewhat complex task. Needed knowledge about sensors, pods and transmitters. Different applications produce a multitude of different transmitters. The trend is clear. A configurable Smart transmitter is not limited to the extent of temperature but also points out short circuits, breaks and many other functions in pursuance of the recommendations of Namur. High-end instruments are classified according to SIL and are approved for applications in areas of protection antiexplosivas. 4 Common signaling20 mA is increasingly complemented by digital (through protocols) or replaced by the same signs.

The transmitters become increasingly more in microcomputer specialist for industrial application.