Zero and Tare, what's the difference?

Our customers often call to find out why their high accuracy balance is not giving the results they expected. Often environmental factors such as, wind, vibrations or even atmospheric pressures can skew results or cause the balance to bounce between a result (not settle).

Sometimes though, the simple fix is to properly ‘Zero’ and ‘Tare’ the scale/balance before weighing. Technically they both make the scale read ‘0’ so what is the difference?

What does Zero mean?

In simple terms zeroing a scale uses internal technology to set the scale to zero reducing the effects of external factors or any calibration drift over time influencing the results.

What does Tare mean?

Taring a scale or balance means to set the readout to zero ready to weigh and is usually used in conjunction with a container or vessel. In effect tare subtracts and additional weight that you do not want to measure in the results such as a beaker, or moisture balance sample pan.

You do not have to tare if you want to use the scale without any additional apparatus. An example of this may be a jeweller’s scale weighing gems or precious metals one at a time.

Why is it important to Tare?

On the scale will be a tare button, when you turn the scale on it may say 0.000g it may also say 0.001g or you may need to put a container on the scale to hold a quantity of items or material.

By pressing the tare button the scale will then display 0.000g so that the container or error can be removed from the weight.

Why this sometimes causes issues or confusion?

Taring a scale subtracts the current weight on the scale, so if there was nothing on the scale and it was measuring 0.001 due to an external factor; say the scale was still settling after being put into a room or there is a dust build up. If you then tare the scale without zeroing, it will now read 0.000g but it has subtracted 0.001g from zero. If you then weigh your material that should weigh 0.022g the scale will read 0.021g as it has subtracted the original 0.001g error as an offset.

Companies like scalesandbalances.co.uk sell extremely precise industrial, commercial and lab equipment. As you can imagine at this level of accuracy this could be a huge problem for our customers. If this was a pharmaceutical company the dose of the prescription could be incorrect. Which is why it is so important to set up your scale/balance properly.

Additionally, you can cause damage to the scale or balance if the capacity is exceeded by introducing a heavy container. For example, if your capacity is 1200g and your container weighs 100g if you put more than 1100g into the container you can strain the load cell despite the scale reading 0g with the empty container in situ.

How to properly Zero and Tare a scale or balance.

Firstly, ensure your scale, balance or moisture analyser is properly calibrated. If you have calibration weights then great, follow your usual due diligence in your internal processes. If you do not, then you can purchase them from scalesandbalances.co.uk. Alternatively, it’s highly recommended you have your equipment calibrated at least yearly. You can have this done by us, just get in touch and we will take care of the rest. This will reduce any calibration drift.

Additionally, if you have recently moved your scale or the something has changed in the environment, allow the scale to settle for a period of time. (This will vary depending on the scale/balance.)

So, you are calibrated, you have left your scale to settle, and you are ready to go; turn on your scale and without anything on the scale pan press the zero button.

Once complete put your container or vessel onto the pan. This will show on the scale and an increase from 0. Press the tare button which will then reset the reading to 0. The scale is now ready start measuring. Note: with the scale set at 0 as you take off your vessel or container, it will go below 0, this is fine!

Other things to consider – Zero-tracking

If you are working in a dirty, dusty or damp environment often found in food processing environments. For example, a washdown scale may build up with food residue influencing your results. Fortunately, many scale manufacturers build in a zero-tracking function that will account for this. It will minutely adjust the scale when it detects that the scale is empty and finds an anomalous result. When the buildup reaches a threshold and becomes too offset from the original zero, the scale will give an error message. Simply clean the scale and perform the Zero and Tare process again before continuing to weigh.

Conclusion

In conclusion there is a difference between zero and tare as they do slightly different things. By using both in conjunction you will improve your weighing accuracy and protect your equipment.