FAQ for Fluid Sensors

Fluid sensors measure process values such as pressure, flow, fill level and temperature in liquid or gaseous media. They enable precise process monitoring in real time and help to increase efficiency.

Fluid sensors are used in industries such as the food and beverage industry, electronics manufacturing and plant engineering. They are often used in cooling circuits, in monitoring production processes and in overflow protection. 

Yes, many fluid sensors have robust stainless steel 316L housings and can withstand harsh ambient conditions such as high temperatures, aggressive media or mechanical stress.

While LevelTech level sensors are used for liquid, pasty, sticky and solid media, wenglor pressure, temperature and flow sensors offer a reliable solution for gases and aqueous media.

Flow sensors work according to the calorimetric principle in which a heated measuring probe is cooled by the medium. In addition to the flow velocity, the temperature of medium can also be measured reliably.

Flow sensors should be installed in risers or closed systems as there are uniform flow conditions. Drop lines or open pipes can falsify measurements and should be avoided.

wenglor flow sensors only measure the flow velocity, but allow the volumetric flow to be estimated by converting the installation parameters. The volumetric flow rate is calculated from the flow velocity and the effective cross-sectional area of the medium:

Q = v * A
Q = volumetric flow
v = flow velocity
A = effective cross-sectional area

The cross-sectional area of a tube is the inner tube diameter minus the area displaced by the measuring rod. Since this area is difficult to determine precisely in the real installation situation, the volumetric flow estimation remains subject to measuring errors. wenglor offers supporting software for this as a download.

To the software

Pressure sensors measure the hydrostatic pressure, which is proportional to the filling height. In addition, LevelTech sensors offer selective detection to monitor limit values or distinguish filling media from each other.

The calorimetric measuring principle is based on the thermal conductivity of the medium. As liquids have different thermal properties, calorimetric sensors must be matched to the respective medium for high measuring accuracy. wenglor calibrates these sensors on water. Water mixtures with additives such as glycol or viscous media can therefore cause larger measuring errors. The more the thermal conductivity of the medium deviates from that of water, the higher the potential measuring error.

With the calorimetric measuring principle, the flow is measured through a heating and cooling phase. The measuring probe is first heated to a temperature just above the temperature of medium. After the heating phase is interrupted, the temperature is measured again. The flow velocity can be determined from the heat loss within a defined period of time, taking into account the thermal conductivity of the medium.

The heating of the measuring probe can lead to slight heating of the medium in its immediate vicinity. For more precise temperature measurements, it is therefore recommended to use temperature sensors.

Yes, the foam and barrier layer detection by fill-level sensors is based on frequency stroke technology. The medium influences the capacitance of a capacitor, which forms a resonance circuit with an integrated coil. The resonance frequency changes depending on the medium, which allows the sensor to distinguish between liquid and foam.

With selective level measurement, it is checked whether a medium reaches a certain point in the tank, for example for limit value detection. Continuous level measurement, on the other hand, records the level of the medium over the entire measuring range, enabling precise monitoring and control.

Some pressure sensors measure pressure and temperature simultaneously, depending on the product variant. This combination saves space and reduces installation effort. Thus, monitoring process values is more efficient without the need for additional sensors.

Relative pressure is measured in comparison to ambient pressure, which can be used to determine overpressure or partial vacuum. Absolute pressure, on the other hand, refers to the pressure compared to vacuum and provides an independent reference that is not influenced by external conditions.

With IO-Link, sensors can be parameterized remotely, diagnostic data read out and exchanged faster. This saves time, prevents breakdowns and increases precision through loss-free digital signal transmission.