| 摘要 |
A flame monitoring means is arranged for selective use with an ionisation sensor (2) or a UV-sensor (3) which are connected in series with a first capacitor (7) to an a.c. voltage (U1). The sensor current charges up the capacitor (7). A threshold switch (74) provides for voltage-dependent discharging of the capacitor (7) and transmits the charge thereof partly to a second capacitor (15), and changes the charge thereof. The voltage thereof influences the input (19) of a trigger stage (42, 43, 44). An output switch (44) of the trigger stage short-circuits the supply circuit of a flame relay (34) in a temporally restricted permissible switching cycle. In the short-circuited condition, a capacitor (35) is discharged by way of the flame relay (34) which is then energised, and the subsequent charging current holds the flame relay (34) in an energised condition The output switch (44) also short-circuits a further capacitor (60) and, by way of a trigger circuit (56, 55), controls a flap (53) for masking the UV-radiation for a restricted period of time. Only the restricted UV-radiation permits the production of the permissible switching cycle, so that the flame relay (34) remains energised. <IMAGE> |
