| 摘要 |
An ignition system test instrument used on spark ignited engines includes a housing having a spark chamber. A sleeve with an open and a closed end is slidably mounted over the housing. A compression chamber is formed between the sleeve closed end and the housing. An air passage connecting the spark and compression chambers extends through the housing. The sleeve can be moved relative to the housing, from a lower to an upper position to compress the air in the compression chamber and the spark chamber. A pair of electrodes is mounted to the housing and extend into the spark chamber to form a spark gap. The electrodes are connected in circuit to an engine ignition voltage source. With the spark gap under pressure, the engine can be turned over and the arc (if any) between the electrodes can be observed. A pressure gauge is carried by the housing for sensing and indicating the air pressure in the spark chamber. A housing groove with a frusto-conical surface, and a diametrically expandable ring received in its groove, provide a frictional holding means for holding, against the force of the pressurized air, the sleeve in whatever upper position it is moved to, yet the holding force provided can be easily overcome by applying manual force to the sleeve to change its position relative to the housing.
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