The 600-IFD-140-SRS, new version of 600-IFD-140J, is a SIL2 flame ionization monitor and control relay which operates in the rectification mode. An isolated current limited 230VAC 50Hz a. c. supply is applied between the flame rod and the burner or pilot pipe (ground connected). In the absence of flame the resistance between the rod and the ground has a high value, therefore no current flows.
In the presence of a flame, the area of ionized gas around the rod presents a lower impedence allowing a small current to flow. This current will have a d.c. content which is related to the ratio of rod to ground area. The 600-IFD-140-SRS monitors this small current, displays its d.c. value on a 10 color segments bar graph and operates a relay when the current excees 2µA (flame present relay). Both relays have volt free change over contacts that are available for the user.