Parcel Scales

How to make a decision about what model of scales to purchase?

It may be quite a challenge to decide what to buy, especially when it goes about such a delicate device as scales. From the one side, weight remains weight and some customers may ask whether it really matters what model of scales to purchase to fulfill a weighing task.

We in PCE Instruments are sure that making a choice of the measuring or weighing device is a serious task and plays an important role. That is why, in case of doubts or questions, you are welcome to contact us: you may use either consulting hotline of PCE Instruments 02903 - 976 99 – 50 or email.

Our specialists are ready to share their knowledge with you and find the solution for your task together with you. Even if you have got some unusual task requiring a special approach, we are ready to take the challenge. Please, describe what you need, and we’ll find a way to create a new design and adapt the software especially for your requirement.

A few recommendations below may help you to make the right choice, and we invite you to read this short text before making the final decision about selecting and purchasing a new measuring device.

If the decision is not easy, first of all, try to make it clear for yourself, what you need, by considering the following:

- Is there any need in verification of the weighing procedure (is there a requirement from the legal authorities)?
- Determine the materials to be weighed (Max. / Min. weight)
- What are the sufficient values for accuracy / resolution / repeatability?
- Are there special requirements to the size of the platform?
- What are the desirable functions the scales should perform?
- Should the data from the scales be further processed after weighing or not?
- Desirable price range

Is there any need in verification of the weighing procedure (is there a requirement from the legal authorities)?

Sometimes, there is an opinion that it is always better to have something than not to have, if it goes about extra papers, documents, proofs and similar. In case of parcel scales, it is not quite the case. Verification is a special procedure which will not particularly influence the precision and accuracy of your scales and it may turn out that for your tape of application, it is absolutely unnecessary. That is why, before making a decision, determine what the main purpose and place of application will be and as a confirmation, you can consult the verification office in your area.

As a customer, you may have a desire to get extra security and confidence that the device you are purchasing is an accurate and reliable weighing instrument. We fully understand that, and in case you find out that a verification is not mandatory, we offer you a good option: calibration certificate. The latter is an official document containing all the necessary information about the measurement deviations, errors, repeatability and other parameters, and thus, you will get a better idea about your device and what to expect from it.

Determine the materials to be weighed (Max. / Min. weight)

Since parcel scales are expected to give quite precise results, the resolution and accuracy are the parameters to care about. They are connected with the weight that will regularly be put on them. Since with the increase of the weight the parameters may change and get worse, it is desirable to avoid overloading of a certain model of scales with the weight which the device is not suitable for. So, your further task is to determine the minimum and maximum weight of the parcels which you are going to weigh. If there is a possibility that a need to weighing bigger load may arise in future, the scales can be modified by adding a few better load cells – this will solve the problem with resolution and accuracy but will also influence the price of the device. That is why, weigh determination is an essential point to think about.

What are the sufficient values for accuracy / resolution / repeatability?

One of the most frequent mistakes is a confusion between resolution, accuracy and repeatability and the role these parameters play in the process of weighing. Depending on what an accent is made on, the parcel scales can be adjusted correspondingly. In case of this type of scales, resolution is very important. In general, there is a similar principle as for other types of scales. If the measuring accuracy is not specified, the rule for the parcel balances is that the measurement deviation is the resolution value multiplied by 3 or 4. A buffer "factor 10" for the parcel scales can be arranged by the user, which, in any case, will give him confidence in measurements. Example: If the balances have the resolution 0.1 g, then a measurement deviation of approx. ± 0.3 g ... ± 0.4 g has to be assumed (unless otherwise described). However, if the user wants to have the measuring accuracy of 0.1 g, then he should look for a balance with the resolution of 0.01 g (factor 10).

As stated above, calibration certificate may provide an operator with all the information concerning deviation, repeatability and similar.

For sure, multiple weighing and use over longer periods of time lead to drifting of the scales and the measuring error becomes bigger. A solution may be to have a personal weight set, with the help of which the parcel scales can be regularly checked and, on demand, adjusted.

Are there special requirements to the size of the platform?

Platform size plays an incredibly important role in the weighing platform, as well as how well the load fits on the platform. Maximum load and accuracy are connected with the platform size and that is why it is another issue to solve. When weighing an attention should be paid to the position of the load (parcel) on the platform. Leverage effect may occur, if the parcel is not placed correctly or does not quite fit, and this may be compensated by the cells of the scales, but for sure, it is better and recommended to place the parcel correctly from the very beginning, with the center of gravity in the center of the platform. In general, the smaller the weighing platform is, the more accurate the scales / balances are. For various weighing tasks, there may be various solutions found, like, for example, weighing of suspended loads, but if it goes about platform, it is definitely a point which should not be underestimated and neglected.

What are the desirable functions the scales should perform?

This question can and should be answered only by the user / the operator, who is going to use the particular scales regularly. A certain model of scales may have numerous functions, which is not always necessary for all the users. In addition, one may function may be needed sometimes, but for different applications (like for example, piece counting function), and it is important to consider this to make an absolutely right choice. A long list of functions is not always the best solution for a certain user. That is why we recommend, first of all, to clearly define what you are going to use the device for and only then make a decision. The device you choose, should meet exactly the requirement you have, otherwise, no matter, how interesting it may from the purchasing aspect point of view, it may turn out to be inapplicable for your weighing task.

Should the data from the scales be further processed after weighing or not?

Modern weighing equipment is often digital, which means that there are many possibilities which they offer, besides direct weighing, for example, there may be analogue outputs, interfaces, USB or LAN interfaces, possibilities for connection to printer or scanner, saving the data to the USB stick for further processing on the computer, data storage and many others. In fact, to produce the scales with all these elements is much easier and cheaper than to install them later on a ready-made device. It may seem to the customer that certain functions are not necessary at the moment; at that point, we ever recommend to think a bit forward and try to predict if there is any possibility that some of the above-mentioned features might be necessary in the future. Preliminary installation may turn out to be very helpful and you will save the extra costs later.

Desirable price range

If you have succeeded in answering all the questions and in making it clear what model of the parcel scales you need for your weighing tasks, it may turn out that there are a few models available that may meet your requirements, but that are from different price ranges. Then, you should carefully study the technical specifications and select the device which will really facilitate and accelerate the weighing process and improve your performance. Not always it is the most expensive model, but not always – the cheapest. Saving money just by buying the cheapest device is not a correct solution, and that is why we recommend to look at this problem from different angles and make an investment into a device which will bring use and good result in future, but not save a bit of money right now.