# Non-Real-Time Wireless System for Lightning Effect Measurements
## 3 Conception of Measuring System  
The first example is a fiber optic measurement system with real-time digital data transmission. Optical transmission and effective shielding ensures a galvanic separation (from the measurement point) and resistance to electromagnetic interferences, which can be induced in the measuring connections in the case of the conductive path (Figure 1). Such a solution allows for obtaining higher accuracy of the conducted measurements [37,38]. Another example is an optical fiber system using analog transmission [39]. The analog-to-digital conversion takes place in the recording device and the measuring probe can be powered by PoF technology. However, analog circuits are sensitive to temperature changes and need to be calibrated regularly [40]. In a measuring system based on analog transmission strong electromagnetic interference that could disturb the real-time transmission is important to consider. The solution to this problem is to store data (the measurement samples) in the probe's memory. After the electromagnetic noise ceases, collected samples can be transmitted to the recorder. The assumptions of the designed measurement system were to enable the observation of the surge pulses in accordance with the international standards. [PERSON]'s law says that the requirement for the correct reproduction of an analog signal is to ensure a sampling rate greater than twice the maximum frequency of signal harmonic [41]. As mentioned, a typical rise time of the wave is 6.4 us, therefore we decided to build a measurement system between 10 and 30 MHz of sampling rate. To ensure the accuracy of mapping the signal with variable polarization, an 8-bit converter is insufficient. The minimum bit resolution is 12 (for the entire measuring range). Sampling up to 30 MHz while writing 2 bytes means that the control processor has to write 480 Mbps. Therefore, two solutions are possible: microprocessors in the 8-bit architecture working with a high frequency of the clock or 32-bit equipped with an oscillator working twice as slow. It is necessary to record more than 8 bits simultaneously. Note that the maximum clock frequency of a microprocessor does not imply its ability to perform calculations. In each system, there are from one to several instructions per clock tick, and the procedure of reading the value at the input and writing it to the appropriate memory location may take up to several clock cycles. This means that the clock frequency should be selected appropriately higher (multiplied by the number of clock cycles needed to complete the entire recording procedure). It is not possible to use a ready-made microcomputer due to its dimensions and energy consumption. The measuring system under development must meet the criterion  
Figure 2: Pulse of the WF4 type, representing the impact of lightning (DO-160 standard for avionics testing) [9,10,36]. of continuous operation throughout the day, which means that the amount of energy consumption is important. Therefore, a low-level solution should be used: a microprocessor with computing power similar to the need (with the smallest possible number of peripherals). The whole device should be small and compact to allow measurements to be made in any (difficult to reach) place. Therefore, it is not possible to use batteries with very high capacity, so that they do not constitute more than 70% of the volume of the entire device. The solution to the problem of selecting a microprocessor that meets the criteria of low energy consumption and high operating frequency may be the use of an external RAM. This solution allows transferring the record at high speed to an external system dedicated to this task. The microprocessor is only a supervisor of this process. The memory must be selected in terms of maximum write speed to ensure throughput of 320 Mbps. There are two choices, also depending on the analog-to-digital converter used: serial or parallel communication. The use of serial communication requires the use of memory and a 480 Mbps converter.