FEATURE Sensors & Sensing Systems Measuring strain with BLE
Matt Nicholas, product design manager at sensor and signal- conditioning specialist Mantracourt, explains how the company’s B24 Bluetooth strain transmitter offers a good balance between wireless functionality and cost
T
he strain bridge measurement is found in a wide range of industrial sensors, typically load cells, to measure forces such
as tension and compression, or in other sensors using Wheatstone bridge circuits, such as pressure or torque transducers. Before wireless technologies became popular, any time engineers needed to take a load-cell reading, they would (and many still do) rely on a physical connection to it. This would require the operator to directly plug in their hand terminal to the load cell to take a reading, or use a human machine interface (HMI) to display the data from multiple sensors. This setup is fi ne for a single load cell, but with a few more units the complexity begins to add up. The cabling and installation costs of wiring such a system can often end up being more than the load cells themselves, adding time, eff ort and cost.
Wireless options The options for wireless transmission are varied, from low-power 2.4GHz devices, which can transmit on multiple channels and are remarkably tolerant of radio frequency interference, to devices that use mesh or star network topologies. These networks are more sophisticated, self- healing and work at greater range than their non-mesh counterparts; however, this is at the expense of power, resolution and simplicity. Then there are the fully-fl edged, cloud-
26 July/August 2021 | Automation
integrated IoT platforms that may be an overkill if all you need is periodical measurement of the load on a container as bulk material is decanted ahead of it being processed. This on-demand, session-based approach means the operator only takes a reading when needed rather than being inundated with an ongoing live feed from the systems.
While IoT platforms have their merits for accessing information remotely, in real-time and sharing it automatically with staff across a business, sometimes all you need is a quick and easy way of taking a reading using a device you already have, like a smartphone or a tablet, for example. This is why Mantracourt developed the B24 Bluetooth Strain Transmitter. It uses Bluetooth 4.0 Low Energy (BLE 4.0) because it is much more effi cient for portable, battery-powered devices (tablets, smartphones, etc.). The transmitter runs up to ten months on a pair of single AA batteries, and it can easily be used with existing devices since most phones and tablets already have Bluetooth built in. The B24 is a small module that comes in an IP67-rated enclosure, or as a board- only option to be integrated as required. The transmitter is easily wired directly into the load cell using fi eld terminals, and works with sensors across a range of sensitivities, from a few grams to a few hundred tonnes. The result is a versatile transmitter for use anywhere there’s a load cell or strain bridge input, whether in automotive, industrial, agriculture or any
other application – it has even been used on a sailing yacht to monitor strain in a rigging system. One key feature that sets the B24 apart
from other Bluetooth transmitters is its multiple transmission capability. By harnessing the BLE functionality, multiple transmitters can transmit to one device, and one transmitter can be viewed by multiple devices. This one-to-one, one-to- many, many-to-one and many-to-many functionalities open up the access to data. However, the hardware technology is only one half of the story. Being able to use a phone to take a reading is only valuable if the app off ers the same kind of fl exibility and customisation as a dedicated HMI or control system. To achieve this, a specially- developed app for both iOS and Android features customisable dashboards.
Implications These breakthroughs in Bluetooth technology and app customisation mean that engineers have more fl exible options available to them, ranging from complete real-time IoT platforms, to manual measurement, with Bluetooth off ering a cost-eff ective option in between – proving that strain measurement doesn’t have to be expensive.
CONTACT:
Mantracourt Electronics Ltd
www.mantracourt.com
automationmagazine.co.uk
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