Electrode gap checking instrument for spark plugs - measures time function of saw-tooth HV applied to gap using timer and comparator

摘要

The circuit for measuring electrode gaps, esp. for sparking plugs, consists of a high-voltage saw-tooth generator (18) whose output is connected to the spark-gap (20) and to the input of a potential divider and pulse shaper (22). The output pulses are counted in a counter (26) controlled from a timer (42). The time period is corrected (44) for variations in atmospheric pressure. The timer output is taken to a comparator (30) having further inputs from a tolerance determining device (36). The outputs from the comparator are taken to indicators (38, 40) which can be of the 'go' - 'no go' type to show whether the electrode gap is within defined limits.