Continuous Level Sensors and How They Work in Industry

Level is an important parameter that is measured in various industries and across a wide range of applications. Continuous level sensors provide a suitable solution when precision and accuracy is important in determining the exact amount of a liquid or solid in a specified range. This article briefly describes the workings of continuous level sensors.

SmartBob

Figure 1. SmartBob

The SmartBob (Models 2 and TS1) is a reliable level measurement system that determines the level of headroom at a single point on the material surface directly under the mounting location of the sensor. Measuring range is from the tip of the “Bob” when completely retracted to where the Bob encounters the material at the bottom of the container.

Guided Wave Radar

Figure 2. Guided Wave Radar

Guided Wave Radar determines the level of headroom from a single point where the cable is situated in the container. Measuring range is from 14” to 36” beneath the threads on the process connection i.e. upper dead zone, to 4” over the top of the counterbalance weight or the lower dead zone.

Open Air Radar

Figure 3. Open Air Radar

Open Air Radar calculates the level of headroom from a single point on the surface of the material directly below where the unit is pointed. Measuring range is from 14” to 36” beneath the threads on the process connection (upper dead zone). For bulk solids, the Open Air Radar is usually aimed at the discharge to inhibit the signal from bouncing off an angled hopper bottom causing false reflections. For liquids, it is normally pointed in a vertical direction.

3DLevelScanner

Figure 4. 3DLevelScanner

The 3DLevelScanner, available in S, M, MV, ML and MVL models, takes measurements from various points within the silo. These points are utilized to measure the material’s volume in the bin. Measuring range is from 19” beneath the threads on the process connection (upper dead zone). Measurement points are not merely averaged to determine the bin volume. Instead, each point is assigned a “weight” by a sophisticated algorithm to calculate the actual volume of the material in the bin.

RL Acoustic Level Device

Figure 5. RL acoustic level device

The RL acoustic level device determines the level of headroom at a single point on the surface of the material directly below where it is mounted. Measuring range is from 19” beneath the threads on the process connection (upper dead zone).

SmartSonic Ultrasonic Transmitters

Figure 6. SmartSonic ultrasonic transmitter

Ultrasonic transmitters determine the level of headroom from a single point on the surface of the material directly below where the unit is pointed. For liquids, it is normally aimed vertically, while for bulk solids it is pointed at the discharge to prevent the signal from bouncing off an angled hopper bottom causing false reflections. Measuring range is from 4” to 14” below the threads on the process connection (upper dead zone).

Conclusion

Ultrasonic, Radar, and 3DLevelScanners have a default dead zone, or blanking distance, usually from the end of the process connection. This enables the units to stop transmitting once the transmit pulse is applied and before the receiver circuit is switched on to listen for the return echo. If a lower full point is desired, dead zones can be increased. Most producers pre-set the blanking distance in the controller, depending on the unit selected. The dead zone of the SmartBob is from the tip of the sensor probe hanging from the cable when the unit is completely retracted.

This information has been sourced, reviewed and adapted from materials provided by BinMaster.

For more information on this source, please visit BinMaster.