What is the difference between a Digital and Analogue Load Cell?

Strain gauge load cells are the life blood of modern, high performance industrial weighing systems. This fundamental technology has stood the test of time since the first units were produced during the second world war for weighing aircraft.

Fundamentally, load cells are very low deflection metal springs that are designed to behave in a highly repeatable manner as they are loaded and unloaded. The three main families are:

• Cannister (compression and/or tension)
• Bending beam
• Shear beam

They are designed so that their deflection is proportional to the load applied. Strain gauges are bonded to the metal spring element in a specific configuration and their electrical resistance changes as the spring deflects in response to the variations in applied load. This proportional resistance change is used to measure the deflection and hence the applied load.

This concept is true for both analogue and digital load cells, with both technologies continuing to have an important role in industrial weighing.

Analogue Load Cells

In an Analogue load cell, the strain gauge arrangement is supplied with a DC voltage (typically +/- 5 V) from the weight instrument. The change in resistance of the gauges (as the metal element of the load cell deflects) provides a very small, continuous (analogue) voltage output, proportional to the applied load. This output is then amplified by the weight instrumentation and converted to display a weight reading.

Analogue load cells continue to offer high-quality, cost-effective weighing performance, especially in a wide range of floor and bench scales; hopper scales; filling machines and counting scales. However, in applications such as weighbridges, digital load cells offer a number of advantages.

Digital Load Cells

As the name suggests, Digital load cells produce a digital output directly from the cell. This robust signal makes them ideal for weighbridge applications, providing important and tangible benefits for both the manufacturer and end user. The Bilanciai Group have pioneered the development of approved digital weighbridge load cells and have two world-wide patents for this technology.

Each digital load cell has its own on-board electronics, which carry out a number of functions and supply a highly stable, digital representation of the load on each load cell. The load cells at the heart of a weighbridge system form a communication network, allowing direct access to the parameters of individual load cells. The individual calibration data for each load cell is stored in the on-board electronic memory, facilitating factors including system calibration, remote trouble-shooting and replacement should the need arise.

The electronics also measure and record critical operating parameters of the load cell, including temperature fluctuations, load cell inclination, overload events and operational frequency. This capability is harnessed by our powerful Nexia™ Remote Monitoring back-office software tool, which allows our engineers to remotely access weighbridge applications.

Such as our NEXIA™ Remote Diagnostics Software

Hybrid Systems

Analogue load cells can be used with our EMULA Smart junction box as part of a hybrid analogue-digital configuration. This offers some advantages over standard analogue load cell systems in certain applications.

Summary

Both analogue and digital weighbridge load cells continue to offer specific advantages.

It should be remembered that on-board electronics cannot turn a poorly designed load cell into a high accuracy device. For both analogue and digital load cells, the design, materials used and the manufacturing process must be of the highest quality.

If you need replacement load cells for your weighbridge, contact our team today for more information. Here at Weightron Bilanciai, we are experts in weighbridges and industrial scales.