Selecting Continuous Level Sensors

BinMaster 20/06/2024

283 5 minutes read

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A practical approach

Selecting the right sensor for your bin-level monitoring application can seem like ordering off of a menu when you don’t speak the language. There are volumes of information about different types of continuous-level measurement technologies and technical data about how they work.

About continuous level sensors

Although helpful, it’s likely you don’t have time to digest so much information, and bin-level sensors are only a fraction of the equipment you need to worry about. This article will give you high-level knowledge about your options, and let you know what you need to know before calling someone to discuss your needs.

Your investment in being prepared with a few facts will pay off in ruling out technologies that won’t work in your application or won’t fit your budget. When you contact your vendor, you’ll save time if you’re prepared with 10 key pieces of information about your application:

Material being measured
Bulk density of the material in lb/ft3
Material’s propensity to be sticky or create buildup
Corrosiveness of the material
Amount of moisture present
Temperature and pressure in the silo
Excessive noise or vibration
Presence of dust, foam, steam or vapor
Size and shape of the silo
Limitations where the sensor can be mounted on the silo

A few other things you might want to consider for continuous inventory management are:

How often do I need to measure or access the data?
How many people need access to the data? How will the information be shared?
Is viewing one bin at a time OK, or do I need to monitor multiple bins simultaneously?
Do I need notification or alerts if levels reach a certain high or low point?
What are my budgetary constraints for equipment?

When the level of material needs to be monitored on an ongoing basis and the information needs to be accurate, continuous level measurement sensors can output data to a console, using specialised software, send the information to a PLC or the Internet for anywhere, anytime access.

Advanced systems can report the data from all of the bins on site or multiple sites, making it easy to monitor inventory status for an entire operation.

What is a dead zone?

Radar, ultrasonic, and 3D Level Scanners have a default blanking distance commonly referred to as a dead zone. The sensor does not account for or measure that distance. So, you need to account for this distance when setting up the device to trigger alerts when the full level is reached.

For example, if using a 3DLevelScanner, the area from the process connection to the bottom of the device (19 inches) is a dead zone. A measurement to the bottom of the dead zone would be considered a full tank. Dead zones can be increased if a lower full point is desired. Most manufacturers have the dead zone preset in the controller, based on the unit selected.

Weight-and-Cable

A weight-and-cable sensor, or plumb bob sensor, works like an automatic measuring tape, without the danger and hassle of climbing bins to take measurements. The sensor is mounted on the top of the bin, generally 1/6 of the way in from the outer perimeter for the best accuracy.

The sensors are programmed to take measurements at predetermined intervals, such as every 30 minutes, once an hour, every 6 or 8 hours, or once a day. Plumb bob measurements are highly accurate, taking the measurement in the same location with reliable repeatability. Depending on the system selected and operational needs, data is sent to a PLC, console, PC, or to the Internet.

Measuring range is from the tip of the bob (also referred to as a probe or weight) when the cable is fully retracted to where the bob contacts material at the bottom of the vessel. The dead zone is minimal, just 4 to 8 inches measured from the process connection to the tip of the sensor probe hanging from the cable when the unit is fully retracted.

Weight-and-cable sensors measure headroom from a single point on the material surface directly below the sensor’s mounting location.

3DLevelScanner

The acoustic technology used in sensors like BinMaster’s 3DLevelScanners, generically called scanners, differs greatly from other types of sensors. As the name implies, these devices scan the material surface to take multiple measurements, taking into account the high and low spots in the silo.

The data from multiple measuring points is processed using advanced firmware and algorithms, and when combined with the silo’s parameters loaded into the software, provides highly accurate level and volume information.

The measuring range starts at 19” below the threads on the process connection (upper dead zone).

Unlike any other technology, the 3DLevelScanner takes measurements from multiple points within the silo. These points consider irregular material topography to determine the volume of material in the bin. Measurement points are not simply averaged to calculate bin volume – instead, an advanced algorithm assigns each point a “weight” to determine the true volume of material in the bin.

Guided Wave Radar

Guided wave radar utilises time domain reflectometry (TDR) to measure the distance to the material by sending a low-power microwave signal along a cable and calculating the level based on the time of flight.

Guided wave radar is used to measure powders, bulk solids, and liquids. Depending on the material's characteristics, different diameters and lengths of cables are used. Measurement data is output to a PLC, a graphical display on the device, or a local display unit.

The measuring range generally starts from 14” to 36” below the threads on the process connection (upper dead zone), although some of the newer models available state smaller dead zones. Guided wave radar also has a lower dead zone, generally about 4” above the top of the counterbalance weight. It measures the level of headroom at a single point where the cable is located in the vessel to the top of the lower dead zone.

Open Air Radar

Open-air radar transmits radio-frequency (RF) energy to the material surface, and the energy is reflected back, much like sound waves. A small portion of the reflected energy returns to the radar. This returned energy, which is called an echo, is processed to determine the distance to the material in the bin.

There are many different models of open-air radar devices, using different types of antennas and operating frequencies, primarily ranging from 6 GHz to 76 GHz. The model of open-air radar device that will perform successfully in operation will depend on the material and container parameters.

The measuring range varies, with the upper dead zone generally ranging from 14” to 36”, depending on the type of antenna and horn installed on the device. Open-air radar measures the level of headroom at a single point on the material surface directly below where the unit is aimed.

For liquids, it is generally pointed straight down (vertical), and for bulk solids, it is aimed at the discharge to prevent the signal from bouncing off an angled hopper bottom, as this can cause false reflections.

Ultrasonic transmitters

Ultrasonic sensors are used for continuous, non-contact level measurement in tanks, bins, silos, and conveyors. They work by transmitting an ultrasonic pulse of pressurised air to the material's surface in a vessel.

The pulse reflects off the material and returns to the sensor in the form of an echo that is received by a microphone. The sensor then sends the measurement data directly to a control system or display module, with some systems allowing data to be sent to a PC running utility and diagnostic software.

The measuring range generally starts from 4” to 14” below the threads on the process connection (upper dead zone). Ultrasonic measures the level of headroom from a single point on the material surface directly below where the unit is aimed.

For liquids it is generally pointed straight down (vertical), and for bulk solids it is aimed at the discharge to prevent the signal from bouncing off an angled hopper bottom causing false reflections.

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Contact Details

BinMaster

About us

BinMaster/Garner Industries is located in Lincoln, Nebraska, USA.

Operations that struggle with the challenges of inventory management and timely replenishment of all types of powders, bulk solids, or liquids can monitor silo levels on their smartphone, tablet, or desktop with complete solutions from BinMaster. A complete suite of continuous level sensors, point level indicators, material management, and inventory monitoring devices and software simplifies material management while keeping people safe from the risks of climbing silos.

The Lincoln Nebraska, USA company manufactures sensors and software used for monitoring levels in bins, tanks, silos, chutes, and hoppers. Continuous level measurement options include SmartBob cable-based, guided wave radar, laser and 80 GHz non-contact radar, which are all compatible with Binventory™ software. Battery-powered, wireless laser level sensors are compatible with BinView® or FeedView® web apps for remote monitoring.

The unique 3DLevelScanner measures and maps material for volume accuracy and is the only sensor to generate a 3D image of silo contents. BinMaster is the exclusive worldwide supplier of this unique technology and has commissioned these sensors in bins containing powders and solids for over a decade.

Point level indicators provide automated level alerts using rotaries, diaphragm switches, capacitance probes, tilt switches, and vibrating rod level sensors. Dust detection devices alert to baghouse leaks and unsafe particulate levels. Flow detection sensors prevent cross contamination and assist with FSMA compliance for human and animal feeds. Aeration devices keep powders and solids flowing so they don’t pack in hoppers, along bin walls, or in the cone of the vessel

Robust, custom systems can be developed for a single site or networked for every bin, tank, and silo across a multi‐national operation. Add Stockpile Reports for pile inventory using images from an iPhone or drone to a SaaS dashboard. Monitor livestock feed inventory from a phone, tablet, or PC with the FeedView® web application.

BinMaster is US manufacturer certified to ISO 9001 quality management systems – requirements. For more information about BinMaster, visit www.binmaster.com.

What we do in a nutshell

BinMaster provides accurate inventory management for processing industries that store materials in bins, tanks, and silos.

Where we supply to

UK Ireland, Africa, Asia, Australia, South America, North America

Industries we supply to

Chemicals, Energy and Power, Food and Beverage, Glass Ceramics Cement, Metals and Minerals, OEM, Paper and Pulp, Pharmaceutical Cosmetics Toiletries, Plastics and Rubber, Recycling, Tobacco, Water and Wastewater

Something interesting you may not know about us:

BinMaster is a subsidiary of Garner Industries and has fully integrated CNC machining capabilities.

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