John: I have a manual for a Robin Model 4112.
The last paragraph (on testing exposed metal of portable appliances) reads:
Connect the Model 4112 to a socket in the normal way. Switch on and calibrate the [infinity] knob for local site voltage. Plugging in the external probe breaks the earth continuity at the plug. The external earth probe can now be used for the appliance or metal work under test. [My bold type.]
Hope this helps.
The last paragraph (on testing exposed metal of portable appliances) reads:
Connect the Model 4112 to a socket in the normal way. Switch on and calibrate the [infinity] knob for local site voltage. Plugging in the external probe breaks the earth continuity at the plug. The external earth probe can now be used for the appliance or metal work under test. [My bold type.]
Hope this helps.