Description
The TLMB is a temperature limit switch with Pt100 and relay output, manufacturer type Müller METL-L. It does not output a measured value, but switches a relay as soon as the limit value is reached.
It is screwed into pipes or tanks and switches there without an evaluation unit, for example directly to a digital input of a PLC. The process connection and protective tube are made of 1.4571, the protective tube measures Ø 6 mm as standard or Ø 9 mm; the insertion length ranges from 50 to 1000 mm according to the key, the system pressure is PN 25. The housing body and lid are made of PBT GF30, the circuit boards are potted, and the protection class is at least IP 65. The weight is approximately 140 g, and the mounting position is arbitrary.
The switching point is set on site with a magnet: without tools and without opening the housing. Instead of a display, there is a red LED, 360° visible – it lights up as long as the relay is active.
The input has a Pt100 in 3-wire circuit of class B, class A as an option, in the range of -50 ... +200 °C with an accuracy of ±0.5 °C. The switching point is set to 100 °C ex works, the hysteresis is 0.1 °C as standard. The output is a relay with changeover contact: 1 A at 30 VDC or 0.3 A at 125 VAC at resistive load, for more than 100,000 switching cycles. The switch is powered by 24 ... 30 VDC at approx. 35 mA including the relay circuit; the electrical connection is M12x1 eight-pole as the only option.
Please note before ordering: The manufacturer's overview page contradicts the data sheet – it states an open collector with 30 V and 200 mA, the data sheet states a changeover relay with 1 A and ±0.5 °C. We use the values from the data sheet; the output type must be confirmed with the manufacturer before ordering. Measuring and configuring are not possible simultaneously: For HART, pin 5 is connected via a 250 Ω resistor, and in this connection, the relay is not functional. Only the switching point can be changed with the magnet; hysteresis, switching delay, and damping are only possible via the HART tool, interface DEV-HM. The ambient temperature is not the medium temperature: The medium can be up to +200 °C, the electronics in the head only up to +80 °C. A CE mark, explosion protection, and SIL or PL classification are not documented.
Advantages at a glance
- Pt100 3-wire, Class B, Class A as an option
- Range -50 to +200 °C, accuracy ±0.5 °C
- Switching point set on-site with magnet
- Changeover relay 1 A at 30 VDC, more than 100,000 switching cycles
- Red LED, 360° visible
- Protective tube 1.4571, Ø 6 or Ø 9 mm, PN 25
- At least IP 65, potted circuit boards, approx. 140 g