Abstract: A computer system receives a number of different dependent variable data sets, all varying with respect to a single independent variable such as time, and displays a plot of each data set on a different one of a set of graphs, all of the graphs having conforming and preferably identical, aligned scales of the independent variable. The identical scales for the common independent variable are preferably in precise vertical alignment, which allows the viewer to more easily see relationships in the changes of the dependent variable data sets as the independent variable changes.

Abstract: A burner control system periodically tests for and detects an out of range signal level from a flame sensor in the burner. When the system is in standby operation where no flame is present, the control system checks whether the flame signal level is within an abnormal range defined by a low margin level and a threshold level. When the system is in an operational phase where flame is expected, the system checks whether the flame signal level is within an abnormal range defined by a high margin level and the threshold level. Should either check detect the flame signal within an abnormal range, a signal is provided indicating this abnormal condition. Preferably, the abnormal condition is used to control the flashing of an indicator light, fast during standby phase if the flame signal level is too close to the threshold level and more slowly if the flame signal level is too close to the threshold level while flame is present. It is also possible to use two different lights for the indicators.

Abstract: A leak detector for a valve controlling flow of fuel to a combustion chamber employs a fuel concentration sensor in a sensing chamber placed downstream from the valve seat. The valve has a downstream chamber which is in communication by diffusion through an orifice, with a source of pressurized air. By injecting air into the downstream chamber through this orifice after the valve has closed and then measuring with the sensor the fuel concentration within the sensing chamber, excessive fuel leakage by the valve can be detected.