Respondents in an Internet panel survey can often choose which device they use to complete questionnaires: a traditional PC, laptop, tablet computer, or a smartphone. Because all these devices have different screen sizes and modes of data entry, measurement errors may differ between devices. Using data from the Dutch Longitudinal Internet Study for the Social sciences panel, we evaluate which devices respondents use over time. We study the measurement error associated with each device and show that measurement errors are larger on tablets and smartphone than on PCs. To gain insight into the causes of these differences, we study changes in measurement error over time, associated with a switch of devices over two consecutive waves of the panel. We show that within individuals, measurement errors do not change with a switch in device. Therefore, we conclude that the higher measurement error in tablets and smartphones is associated with self-selection of the sample into using a particular device.