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Transmitters Replace Hard-Wired Sensors

March 7, 2003
Endress+Hauser's iTemp line

Dealing with an analog control variable such as temperature has been an overly restrictive and costly issue over the years for many process equipment builders.

"Machine builders and OEMs have traditionally hard-wired temperature sensors directly to I/O," says Jochen Eberheim, division manager of temperature products at Endress+Hauser. He thinks using transmitters is a better way. "By using transmitters instead, builders can save on wiring costs, improve measurement accuracy, and eliminate problems from electrical noise," adds Eberheim.

Transmitters also can help these machine builders with the varied and changing preferences for fieldbuses in a customer's process plant.

In an effort to make life easier for these industrial OEMs, Endress+Hauser has introduced its iTEMP line of temperature transmitters to the North American market. According to Eberheim, the transmitters are small, reliable, accurate, easy to configure, and can diagnose problems.

In North America, most users prefer Foundation fieldbus protocol, while users in Europe and Asia prefer Profibus. Using application-specific integrated circuits (ASICs) in the transmitter electronics helps keep the devices flexible and easy to manufacture. "The use of ASICs allows the production of transmitters that meet specs from Form B to DIN43729, with a choice of 4-20 mA, 4-20 mA with HART, Foundation fieldbus, or Profibus-PA outputs," says Eberheim. "In all cases, the linear temperature output signal is accurate to 0.1% of span."

In Germany, Eberheim says the use of ASICs allows devices to be built and configured quickly. "The lead time for head transmitter delivery has been reduced to two working days in Europe," he says. "In North America, we will also be able to meet customer orders within two working days."

Jerry Spindler, business development manager at E+H, says the company will be ready for OEMs. "Our compact thermometer and DIN rail-mounted transmitters are the types of products we know industrial OEMs in the North American market will want in volume and for immediate delivery," he says. "We will offer an E-direct online store in April that will make it easy for OEMs to order some of our temperature transmitters, along with other instrumentation, including level and pressure sensors and digital displays."

Regardless of the choice of output, many of the transmitters can be configured with a PC using E+H dCare software or ReadWin 2000 software, which can be downloaded for free from the Internet. The software runs on Windows 95/98/NT/2000/XP. Depending on the type of transmitter, calibration and configuration information can be accessed via HART, FF or Profibus connections, making it easy to configure a machine during construction, retrofit, or maintenance.

Housings for field transmitters are available in die-cast aluminum with paint or powder coating or in 316L stainless steel, making them suitable for installation in most process plant applications. Housings are sealed to meet NEMA 4X specs.

Each field transmitter is available with an explosion-proof enclosure that has dual compartments. For example, the TMT 162's enclosure houses the transmitter electronics and liquid crystal digital backlight display in one compartment. A second compartment--mechanically separate but electrically cabled to the first--contains the terminals for the electrical interfaces, such as the sensor inputs and 4-20 mA and HART connections. Universal field transmitter models accept dual inputs from RTDs, T/Cs, and resistance and voltage sensors. Model TMT 162 comes with 4-20 mA output and HART interface; TMT 165 has Foundation fieldbus output.

Head-style (hockey puck) transmitters fit inside standard Form B sensor heads. Most accept inputs from RTDs, T/Cs, and resistance and voltage sensors. Models 187 and 188 accept only a Pt100 RTD or a T/C, respectively. Model TMT 182 has 4-20 mA output and HART interface; TMT 181 comes with programmable 4-20 mA analog output and galvanic isolation; TMT 180 is designed for RTD without galvanic isolation; TMT 187/188 are fixed-range devices with 4-20 mA output; TMT 184 has a Profibus-PA interface.

DIN rail transmitters are intrinsically safe to FM and CSA specification, making them suitable for use in hazardous areas. Models TMT 121 and 122 accept most RTDs and T/C inputs, while TMT 127 accepts only a Pt100 RTD and TMT 128 accepts only T/Cs.

Most of the devices have the necessary certifications from ATEX, FM, CSA, UL, and other organizations.

For more information call 888-ENDRESS or browse to www.us.endress.com.