On both boards was also included an RJ45 (ethernet) port. An ethernet cable was chosen to consolidate the 6 wires required to power the LED and communicate with the sensor into a single cable (leaving two of the eight wires unused). The choice was made to use a ubiquitous, easily interchangeable cable so that any cable of suitable length could be selected as required dependent on location. This design then allows the detector and Raspberry Pi to be located any distance apart by simply choosing a longer or shorter ethernet cable (Figure ). Further testing of the device was carried out to determine the best operation protocol. It was found slugs were much easier to visualise graphically if the sensor channel data is baselined to the absorbance of the system solvent (see Supplementary Information, Figure ). This then results in a clear positive or negative peak in the trace when a slug is passing the detector. LED brightness was also tested, and full power was found to give the best signal to noise ratio (the LED is not too bright to cause saturation of the detector).