Sensors in production
Litronic FMS P78 planar sensor
Small, fine, excellent: The Liebherr P78 sensor in conjunction with the Liebherr FMS moisture measuring installation has become indispensable for many industrial processes. The moisture measuring installation was invented in 1985 at the Bad Schussenried factory. Measurement by the Liebherr sensor system is based on the physical principle of capacitance determination in the high-frequency stray field. In addition to their high precision and robustness, the measuring devices from Bad Schussenried are characterised by their reproducibility.
Once the sensor has been calibrated, further measuring points can be set up or devices renewed on this basis at any time without great effort. The plant thus always remains reliable, regardless of its previous term and age.
Sensor/electronics evaluation
| Physical principle | Capacity determination in the high frequency stray field |
| Frequency | 20 MHz |
| Measurement location | Measurement location: Outside silo via baffle plate, on belt with sliding shoe carriage, pipes, screw conveyors, tank, etc. |
| Measuring range | 0-100% moisture content |
| Capacity resolution | 3 fF |
| Update cycle | 32.64 ms |
| Sampling rate mean value counter | 16 – 25 106 |
| Maximum attainable measuring accuracy | +/- 0.05 % moisture content 1.) |
| Measurement value transfer | digital: RS-485, multiprocessor log |
| Max. number of sensors on the bus | 16 |
| Maximum bus length | 1200 m |
| Power supply | 8 - 30V, 0.4 VA |
| Temperature measurement measuring range | -10 – 90 °C |
| Measuring accuracy temperature measurement | +/- 0.5 °C |
| Operating ambient temperature | 5 – 72 °C |
| Working temperature - electronics | -20 – 80 °C |
| Storage temperature | -25 – 80 °C |
| Protection class | IP68 |
| Connection cable type | UNITRONIC®ROBUST C 7x0.14 shielded |
| Connection cable length | 6 m |
| Wearing protection: | Zirconium oxide (ZrO2Al2O3) |
| Housing/flange material | V4A (1.4404) |
| Dimensions: Ø/Height | 78/57 mm alternatively: 30/94 mm |
| Weight without cable | 0.500 kg |
| Weight clamping flange | 0.300 kg |
1) representative of the batch or the time window in the Contiprocess, in conjunction with the associated Litronic-FMS evaluation device, material-dependent, with ideal flow behaviour and with proper calibration.
Characteristics
• Pure capacitive measuring method
• Sensor exchange without recalibration
• Sensitivity adjustable in 3 steps
• Integrated microprocessor with mean value calculator
• Material flow detection
• Temperature compensation
• Limit value evaluation
• Direct digital measurement value determination
• Highly wear-resistant ceramic shield
• Stainless steel housing
- Indirect measuring method: Capacity determination in the high frequency stray field. This method uses the different dielectric constant (permittivity) of water and different materials (solids and liquids).
- Fully reproducible sensors: If the plant is subsequently extended with sensors or if sensors are replaced, no recalibration is necessary thanks to the built-in microprocessor.
- Waterproof and dustproof: The sensor is also suitable for the harshest environments thanks to its IP68 protection class.
- Very hard wearing protection: The sensor surface consists of a 2 mm thin zirconium oxide ceramic.
- Process control and regulation: Thanks to extensive interfaces, the moisture measurement can be integrated into process control systems and controls.
- Cost saving: Time-consuming and costly laboratory analyses are no longer necessary or can be reduced.
- Limit values: Maximum or minimum limits can be set using the software. Light or sound signals can be triggered if required.
- Mean value calculator: The sensor passes on already averaged values to the FMS evaluation and transfer module.
- Increased temperature ranges: For use at increased material temperatures, we offer our P78-T sensor, which is designed for max. 90 °C material temperature.
- Explosion-protected areas: For the applicable equipment category II 2D Ex tb IIIC T85°C Db and II 3D Ex tc IIIC T85°C Dc we use our P78-E sensor.
- Salt and acid: For highly aggressive substances, we use the high-grade material 1.4462 for the P78-H sensors.
- High wear: The Liebherr P78-V sensor is ideally suited for abrasive materials thanks to its 10 mm thick plate.
- Flange adaptations: For sensor installations in pipelines from DN150 and tank installations, we offer our DN80 flange. This is also available as a salt- and acid-resistant version.
- sliding shoe slides: A proven method of installing the sensor on the material using the carriage. Stainless steel, Hardox 400, Vaudit, acid and salt resistant or ceramic lined versions are available.
