Description
The TMMA is a surface temperature sensor on a magnetic base with a display and two limit contacts, manufacturer type Müller METS-WSM.
It is placed on pipes, motors, and housings where no drilling is allowed – attached instead of installed, without interfering with the medium. The spring-loaded measuring surface Ø 6 mm with 1.5 mm travel presses onto the surface, and the Alnico 500 magnetic base holds with 66 N. The sensor body is made of stainless steel 1.4571; with approx. 259 g, PN 25 and at least IP 65 for the electronics, the mounting position is arbitrary.
The device features a four-digit 7-segment display with a head that can be rotated by approximately 330° and a display that can be mirrored by 180°. Settings are made on the device using three buttons or via HART; the measured value can be read on-site without a host computer. The two limit contacts operate as PNP or NPN with 30 VDC and 200 mA; switching delay and failsafe can be set up to 999.9 s.
Measurement is performed with a Pt100 in 4-wire circuit in classes A, B, and AA in the range -50 … +200 °C with a smallest span of 50 K. The output is 4 … 20 mA with HART in the 2-wire loop; the accuracy of the measuring amplifier is 0.3% of the range at 16 bits. The sensor is powered from the HART current loop with 12 … 40 VDC.
Before ordering, please note: The ambient temperature is not the medium temperature – the measuring surface can withstand up to +200 °C, but the electronics in the head only up to +80 °C, and above +85 °C they can be damaged; the sensor sits with the magnet directly on the hot surface, the source does not say how much heat reaches the head. How the adhesive force of 66 N changes with temperature is not documented; the fastening must be checked before use on hot surfaces. Galvanic isolation applies only between switching outputs and measuring amplifier, not against the loop and not against the surface on which the magnet sits. Two limit contacts are only available with M12 five- and eight-pole as well as MIL; a cable gland is not listed. The data sheet only mentions up to -50 … +250 °C on request. For configuration, the HART interface with USB and software (01310-00220) is used. A CE mark, a declaration of conformity, and explosion protection are not documented in the data sheet. The identical version without display and buttons is the TMMB (METS-WTM).
Advantages at a glance
- Attached instead of installed – magnetic base with 66 N from Alnico 500
- Four-digit display, head rotatable by approx. 330°, three buttons or HART
- Pt100 4-wire, classes A, B, and AA, medium -50 … +200 °C
- 4 … 20 mA with HART, accuracy 0.3% of range
- Two limit contacts, switching delay up to 999.9 s