One or more first signals and one or more second signals, wherein the second signal(s) are slowly varying or low frequency signals in comparison with the first signals and are converted from analog to digital by sampling the first signals and the second signals to produce samples thereof for analog-to-digital conversion, subjecting the samples of the first signals to conversion to digital at a certain conversion rate, subjecting the samples of the second signal to conversion to digital by segments so that these segments are subjected to conversion to digital along with the samples of the first signals at the respective conversion rate, and reconstructing digital converted samples of the second signal from the segments subjected to conversion to digital.