A: Serial numbers can be found in various locations depending on the product. For light sensors and MiniMet sensors, the serial number can be found on the end of the cable, close to the connector/wire end on a white section. For DataHog loggers and SpectroSense units, serial numbers can be found inside the battery compartments, these may need to be unscrewed. Our standard display meters have the serial number of the meter and sensor printed on the back of the unit. If you are struggling to identify the serial number of your product, please get in touch with us.