Posted on 06/05/08, under Level Measurement, Principles of Good Measurement · RSS · No Comments
Measuring principle - Capacitance Sensor
The proven capacitive measuring principle is one of the most common measuring principles for level measurement in the industrial measurement technology. Sensor and vessel form the two electrodes of a capacitor. A capacitance change caused by a level change is processed by the integrated electronics and converted into a switching signal. The level measurement is carried out via the complete sensor length without a dead zone. Thanks to cable and rod versions, suitable instruments are available for all applications.
Applications in liquids
Mainly fully insulated instrument versions are used in these applications. Hence measurements of corrosive liquids or adhesive products are no problem. The mounting of the instruments is easy and the rugged construction is the basis for an interference and maintenance free operation.
Applications in bulk solids
Partly insulated versions are preferably used in bulk solids. Also here, we have the proven, rugged configuration as basis for the manifold and reliable use, e.g. in the aggregates and mining industry.
Posted on 30/04/08, under Level Measurement, Principles of Good Measurement · RSS · 2 Comments
Measurement Principle of Ultrasonic Level Transmitters
Short ultrasonic impulses in to range of 10 to 70 kHz are emitted by the transducer to the measured product, reflected by the product surface and received again by the transducer. They spread with sound velocity. The time from emission to reception of the signals is proportional to the level in the vessel. The proven ECHOFOX signal processing filters out the correct level echo reliably from a number of false reflections. An adjustment with empty and full vessel is not necessary!
Application in liquids
Sensors with frequencies between 30 and 70 kHz are used for these applications. They operate independent of product properties and are ideal for water/waste water applications and the measurement of slightly corrosive acids and lyes. Also applications in gas-Ex areas can be equipped with these sensors.
Applications in bulk solids
Sensors with frequencies between 10 to 30 kHz are used for these applications. The lower switching frequency enables a considerably better penetration of dusty atmosphere. An adjustment with medium is not necessary. For applications in dust-Ex areas, approved sensors are available.
Posted on 28/04/08, under Guided Microwave TDR, Level Measurement, Principles of Good Measurement · RSS · No Comments
High frequency microwave pulses are coupled on a cable or rod and guided along the probe. The pulse is reflected by the product surface and received by the processing electronics. This electronics evaluates the echo signal and converts it into a level information. All instruments are preset to the ordered probe length. The shortenable cable and rod versions can be adapted to the individual conditions on site.
Applications in liquids
Density fluctuations, steam generation or strong pressure and temperature fluctuations do not influence the measuring result. Also buildup on the probe or the vessel wall do not influence the measurement. An ideal application is level measurement in a bypass tube where even products with dielectric values below 1.6 can be measured reliably. Also connection tubes - bypass tubes have no influence.
Applications in bulk solids
Typical problems in bulk solids such as e.g. dust and noise generation or condensation do not influence the reliability. Also the shape of the material cone or the product properties, e.g. the change from dry to wet sand do not influence the measuring result. Since the instruments are already preadjusted, setup is limited to connection of the sensor.
