To tare or not to tare? Maybe zero is the answer? We'll discuss what zeroing and taring means and when they should be used. If you're reading this blog, you're probably confused between the two and it's easy to see why: they both seem to set the scale back to zero. Hopefully, after reading this blog you'll understand the differences between the zero and tare key on your new scale and how to use them effectively. 

Zeroing a Scale

On the surface, it appears that pressing both the zero key or the tare key produce the same results. So why have two keys? To start, we'll have to define what each function does. A zero key is used when there is no load applied to the pan. This set point is generally set when the scale is calibrated and should be the true zero of the scale. The zero key should only be used when no load is applied.

Simply put, the zero key should be used for any small adjustments that need to be made. For example, any buildup of foreign material on the scale pan may skew the true zero (such as dirt, rust, or other trace materials), which may be more noticeable on higher resolution scales and balances. You may also need to re-zero the scale if something is sharply dropped on the pan or an object that is way over the capacity of the scale is placed onto the pan.

Taring a Scale

But wait a moment. The tare key also sets the display back to zero. So what's the difference. According to  Merriam-Webster dictionary, tare is defined as "the seed of a vetch". Wait a second, wrong definition. Let's try this again. It is defined as "a deduction from the gross weight of a substance and its container made in allowance for the weight of the container". 

In other words, using the tare key sets the display to zero when a separate container is being used to hold whatever substance being weighed. For example, you may use a weigh boat when measuring how much agarose powder to use to make your electrophoresis gel. You aren't going to want the weight of the boat to skew the powder measurement so you use the tare key to change the zero setpoint to include the weight of the container.

If you're still not quite sure what the difference between zero and tare is, check out the video below. To demonstrate the difference, we used an OHAUS Scout STX422 portable balance which features independent zero and tare buttons.