| 摘要 |
The disclosure depicts apparatus for testing wiring connection patterns in a three-wire AC electrical outlet, comprising a three-wire plug adapted for insertion into an outlet and comprising a line probe, a neutral probe, and a ground probe. In the embodiments illustrated a test circuit connected to the plug includes circuit branches between each of the probes and a common terminal, the branches containing resistance means having different resistance values. An AC electrical meter is connected in one of the circuit branches such that deflection of the needle is proportional to the absolute current flow in that branch and also in the test circuit as a whole. Different wiring connection patterns in a tested outlet produce different series-parallel connections of the circuit branch resistances and thus establish different current flows in the branch including the meter. The meter has a scale upon which a plurality of discrete zones are marked with indicia characterizing the various outlet wiring connection patterns which are possible. Upon insertion of the plug into an outlet, the meter needle is deflected to a particular zone on the scale, thus identifying the particular wiring connection pattern existing in the tested outlet. The location of the needle in the zone gives an indication of absolute line voltage in the outlet. Two disclosed embodiment include a resistor connected between the neutral and ground probes such that an open neutral connection in the outlet may be detected.
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