Accuracy Repeatability and Resolution

As with any measurement system, there are several factors which play a key role. Three of these are: Accuracy, Repeatability and Resolution. The user of the measurement device may need to give thought to these three factors since they may translate into a significant difference in the pricing strategy of the device, or system.
The accuracy of the device may be defined as its ability to adhere to a standard, like those kept by the National Bureau of Standards, or some local authority. It’s repeatability may be defined as the ability of the device to repeat a certain accuracy. It’s resolution is a measure of the devices ability to resolve (or indicate) a value. Consider the following situation.

Imagine that we are going to produce a product that must look and taste good and most importantly it must be consistent so that it is the same each time we use it. Further, lets assume that we are not able to predict what the exact taste should be, nor are we able to predict what the exact color should be. We know approximately what these variables should be, but we will rely on our ability to “tweak” the process to achieve the proper combination.

Once the process values have been achieved, our concern now is for our ability to reproduce these product “set points” on a regular basis. If we were going to automate this process we would look to a system that was repeatable. Absolute accuracy is not an issue here since there was no standard to adhere to except the one that we developed via our “tweaking” method. The product was as good as we wanted it to be and that was it.
Now lets suppose that we found out that our new product was in violation of an industry standard, or we discovered that we were adding more raw materials than we needed to, thus costing us more money to produce the product than necessary. In reality, we were faced with some combination of the two. We had to adhere to a standard for the product to maintain it within the law, but at the same time we didn’t want to be so conservative that we made the cost of producing the product too high, and we could not remain competitive.

The law specified that certain minimum ratios of the product materials had to be adhered to, and that we needed to be accountable to these standards. Here we may need to consider the accuracy of the measuring device to be certain that we maintained the product consistent within the legal standards. Also, our product records needed to demonstrate this accountability. Here clearly we needed accuracy as well as repeatability. In both cases though the measuring device should have been calibrated to provide the user with the maximum resolution possible in order to provide the best indication of the measured variable. If a value of 50 Brix were our target value, certainly a range of say 49 to 51 Brix would provide better resolution than a range of 40 to 60 Brix.
In our next article we will talk about how these three factors (accuracy, repeatability and resolution) may effect the pricing strategy for these measurement products.
For more information contact us

No Comments Yet.

Leave a reply