ANALOGUE vs DIGITAL WEIGHBRIDGE LOADCELLS

Which is better, analogue or digital weighbridge loadcells? What follows is a discussion that highlights the pros and cons of both.

Introduction

While sales people from various scale companies will talk up one type of loadcell over the other (depending on which their company sells), both analogue and digital loadcells are essentially the same thing and often have identical performance capabilities and identical accuracies for Trade Measurement purposes. Digital loadcells, however, include an internal analogue to digital conversion unit (A/D Unit) that requires a proprietary indicator to interpret the digital signal. Analogue loadcells use the analogue to digital conversion unit found in most digital indicators to produce a weight reading. The only difference between the two, therefore, is the location of the A/D Unit.

Both have advantages and disadvantages, and these are expanded upon below.

Digital Loadcells


Advantages
+High Level of Error Reporting
+Software Corner Adjustments


Disadvantages
- More Expensive System
- Limited Indicator Choices/Features
- Tied to Manufacturer's Service Outlets
Digital Loadcells

Digital loadcells are connected to the digital indicator individually. This allows the digital indicator to monitor each loadcell individually for errors. The indicator can also be used by a service technician to adjust the calibration of some loadcells to match them to other loadcells, which is occasionally necessary to ensure the weighbridge reads correctly, no matter where weight is placed on it. This individual loadcell adjustment is known as corner adjustment (even if a loadcell isn't located at a literal corner of the weighbridge).

Because each digital loadcell incorporates its own internal analogue to digital conversion unit (A/D Unit), it will naturally be more expensive than an analogue loadcell which does not include an internal A/D Unit. A digital indicator designed to be used with digital loadcells also tends to be more expensive than one designed to be used with analogue loadcells.

Perhaps the most significant feature of a digital loadcell is that it outputs a proprietary digital signal. What this means is that, if you purchase a Brand A digital loadcell, it will only be able to be interpreted by Brand A's digital indicator. You will typically not be able to use a digital indicator from Brand B or Brand C to work with Brand A's digital loadcell. Once digital loadcells are installed, this effectively ties you to the supplier's servicing organisation and ties you to the range of features that the digital indicator has available. This may or may not represent a limitation to clients.

Analogue Loadcells


Advantages
+ Very Cost Effective
+ Unlimited Indicator and Functionality Choices
+ Unlimited Choice of Service Providers


Disadvantages
- Manual Corner Adjustments
- Lack of High Level Error Reporting
Digital Loadcells

Analogue loadcells are connected together, typically in a junction box mounted on the weighbridge. From there, a single cable connects the junction box to the digital indicator. The analogue signal to the digital indicator is therefore an average reading of all loadcells connected and the digital indicator cannot report on individual loadcells. To adjust corners, a service technician must manually install resistors in the junction box to adjust the calibration of some loadcells to match them to other loadcells, if required. This can result in a lengthier calibration process.

Analogue loadcells output a generic analogue signal. This means that virtually any digital indicator designed to work with analogue loadcells can be used. This prevents a client from being tied to a particular servicing organisation as virtually every servicing organisation can work with analogue loadcells. Note though that some companies may be the sole distributor of certain types of analogue loadcells in Australia. This means that while other servicing companies can service the weighbridge and replace the digital indicator, they may only be able to source replacement loadcells from the original weighbridge installer, often at an inflated cost.

What Does QWM Supply, Analogue or Digital?

QWM can supply either analogue loadcells or digital loadcells. We currently choose to predominantly install weighbridges with analogue loadcells though. For reasons listed above, we feel that our clients should have the freedom to choose whichever service provider they so choose, now and into the future. However, our digital systems are also high quality, reliable and very competitively priced in the market. Our clients can be assured that we will place their interests first in selecting the best components for their weighbridges.