Bad design of scanner (My ENSC304 Assignment1)

1. The Problem

There was a time when I volunteered in a conference and my job was to use a little scanner to scan the bar code of the attendees’ tags. The scanner is a very small device, approximately 3cm*5cm. The interface of the scanner is very simple: the front side has a light indicator and one big blue button, and the back side has one small button with the same blue color.

When I first received the scanner, I figured out very quickly that to scan the bar code I need to hold the big button while the laser light going through the bar and also that the light indicator would flash if it succeeds. However, the problem comes with the small button on the back.

As no label on the back, without instruction I had no idea what this button is for. Later I was told that the small button is for deleting data. If that button is pressed, all the previous scanned data will be deleted. Fortunately, I didn’t press that button before I learned about its functionality. But if I did, all the data that the previous volunteer scanned would be completely lost and could not be retrieved.

Besides, there is no indication when the delete button is pressed. So in case I accidently pressed the button, I wouldn’t know. I was very cautious to make sure I didn’t touch the button while using the scanner, which of course affected my working efficiency. Due to the small size of the device, it was very hard to my fingers away from the delete button.

The scanner gives me hard time to execute my task, which can be considered as Huge Gulf of Execution. User needs to pay extra attention to the back button while working on the device. Without any label or instruction on the device, it is likely for a new user to press that button without knowing the consequence of loosing all the previous data. If user accidently presses the deleting button without knowing the functionality of that button, all the recorded data will be deleted which is actually not what user wants. Even worse, the effect of mistake is not reversible and the loss can be irreparable. On the other hand, the scanner didn’t provide enough feedback for me to interpret its state, i.e. user has no idea whether the deletion of data has been executed or not. This can be considered as a Huge Gulf of Evaluation. Above all, the scanner causes difficulties for users to execute the tasks, and evaluate the result of their actions.

2. Design Principles

The scanner violated the following principles:

a. Make It Visible

The delete button has no label beside and placed at the back with a small size. Without instruction, user will be struggling to figure out its functionality, or user won’t know the scanner has the function to delete the previous scanned data by pressing a button.

b. Provide Feedback

The scanner fails to provide any feedback for pressing the delete button.

c. Make Error Effect Reversible

The scanner has almost irreparable error effect. If the delete button is pressed accidently before backup, the data can never be retrieved.

3. Solutions

To solve the problems I observed, I have the following suggestions to modify the design.

1. A label should be added on the back side, clearly indicating that the button on the back is for deleting all the data.

2. It should use sound or light to provide sufficient feedback for the delete operation. For example, when that button is pressed and the data is deleted, the device can make a “bee” sound. The front indicator light can also flash with red color (the light flashes in green when the bar code is successfully scanned).

3. For such a small device with compact interface, it is not a good idea to have a screen to interact with user. In order to reduce the chance of mistake in operations, the deletion button should be made caved into the flat surface. This way, only when users intentionally press the button very hard, can the delete operation be executed.