How to Calibrate a Scale

How to Calibrate a Scale

Not all scales can be calibrated, smaller cheaper scales will instead have a tare or zero button. Other more accurate scales will have a calibration mode that will allow calibration with standard calibration weights. Refer to the user manual for the scales you are using to find out the correct procedure. 

Many cheaper smaller digital scales don’t need scale calibration after they leave the factory, apart from zeroing on startup and optionally with the tare button. But for this reason, these scales are not as accurate as ones that can be calibrated properly with a set of calibration weights. 

Why does a Scale need to be calibrated anyway?

calibrate digital scale

All scales whether they are super accurate lab scales, a simple digital pocket scale, or your trusty old bathroom scales that has been doing its job for many years need calibration at some point. 

Some scales like those in your bathroom are not overly important if they drift off and are inaccurate by a couple of percent so they are calibrated once at the factory and they are good to go for the rest of their lives. 

Alternatively to this for scales where you need more accuracy and precision, you will need to perform calibrations more often. Something that needs to measure very accurately and repeatably, like a reloading scale will need to be calibrated every time you use it. 

This is because many things change how a scale measures, from the temperature of the springs inside them making them easier to compress. To the amount of friction within the mechanics of the device to changes in weight of the device itself as it ages. Many things can cause a scale to change its readings through a given day and over its life. 

This is why it’s important to calibrate and why the more precise the device the more often and more involved the calibration process will need to be. 

For example for high precision devices, they may need a range of calibration weights so that the device can map out the variations in its measurements rather than just a single measurement. They also need to have this calibration completed every time they are used. 

What is tare or zero function on a scale?

The tare or zero button on a digital scale tells the scale to reset its measurement to zero. This can be done with a load applied or without so that a reading can be taken from a zero point seat by the user. The zero or tare button has two main uses and is how to calibrate a digital scale without a weight.

tare a scale
  1. To calibrate the zero point of the scale when it is started or after the scale is used to reset the zero point when some drift has occurred over time. This is very important for smaller cheaper scales that may have significant drift as this allows the zero point to be taken regularly increasing the accuracy of the scales.
  1. To allow measurements to be made after excluding the weight of the container from the measurement. You may want to do this when there is something you want to measure that will need to be kept in a bowl. Rather than weighing the bowl then the bowl with the material to be measured you just need to add the bowl to the scale. Tare the scale with the container on it and then add your material to be weighed. This will allow measurements with no maths involved. 

Calibration Weights

To calibrate any scale you will need calibration weights, these are a set of weights that are very accurately tuned to a specific mass. These are placed on the scales during the calibration phase to set the scales at different masses. 

Neewer 8 Pieces 1000 Gram Stainless Steel Calibration Weight Set

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This Neewer calibration weight set is perfect for almost any application. it contains a set of 8 weights ranging from 10 grams up to 500 grams for calibrating most kinds of scales. It comes with tweezers for handling the weights and a box to keep them safe and organized. this will save them from being dropped or bumped and makes transport much easier.

TOODOO 1g 2g 5g 10g 20g Gram Calibration Weight Set

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The TooDoo Calibration weight set is perfect for a smaller capacity scale. They are nice and cheap and include everything you need. With a couple of weights they will do the job for most people.

How often should weighing scales be calibrated

A scale should be calibrated according to the manufacturer of the scales, you can find this information in the user manual. But in general the more accurate you need the scale to be the more often it should be calibrated. 

Generally, as a simple rule of thumb, if you are not sure if the scale should be calibrated then you should calibrate it. 

Do I need to calibrate my scale?

For most scales used at home, like a bathroom scale and a kitchen scale the answer is no. These scales are designed to self zero to try and remain as accurate as possible, but the main reason is that a normal person does not need to measure anything so accurately that the scale matters.

Calibration weights

For example: If your bathroom scales measure you 200g lighter than you are it is unlikely to affect anything in your day to day life. Also, the fact that this measurement is consistently inaccurate in the same direction does not stop someone from tracking their weight. 

If you weigh 70.5kgs today and 71kgs in a week the difference is the important part and would show an increase of 0.5kgs. The fact that your real weight would be 70.3kgs and 70.8kgs is not important. The change in weight is what is important. 

Alternatively, if you are working in a lab, or measuring medications where a high level of accuracy is needed then maybe you will need to calibrate your scales. To find out if this is important you need to know the tolerance of the measurements you are taking. Most scales will have a minimum measurement that they can read and this determines how sensitive the scale and if the scale will need to be calibrated. 

A simple rule for this is, the higher the accuracy you need the more expensive the scale you will need, and the more scale calibration will be important for your scale to keep accurate. 

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