  IoT devices, edge devices and embedded devices, in general, are ubiquitous.
The energy consumption of such devices is important both due to the total
number of devices deployed and because such devices are often battery-powered.
Hence, improving the energy efficiency of such high-performance embedded
systems is crucial. The first step to decreasing energy consumption is to
accurately measure it, as we base our conclusions and decisions on the
measurements. Given the importance of the measurements, it surprised us that
most publications dedicate little space and effort to the description of their
experimental setup.
  One variable of importance of the measurement system is the sampling
frequency, e.g. how often the continuous signal's voltage and current are
measured per second. In this paper, we systematically explore the impact of the
sampling frequency on the accuracy of the measurement system. We measure the
energy consumption of a Hardkernel Odroid-XU4 board executing nine Rodinia
benchmarks with a wide range of runtimes and options at 4kHz, which is the
standard sampling frequency of our measurement system. We show that one needs
to measure at least at 350Hz to achieve equivalent results in comparison to the
original power traces. Sampling at 1Hz (e.g. Hardkernel SmartPower2) results in
a maximum error of 80%.
