It's easy to add relays to a Greyline instrument. Power the unit off, plug in the relay board and power back on. The instrument detects the new hardware and automatically loads the menu system for calibration. In this video we add four relays to a Greyline DFM 5.0 Doppler Flow Meter. Following the same procedure you can also add a data logger. It takes just a couple of minutes for complete installation.