The latest circuit design permits the instrument to operate with the minimum of influence from earth voltage and earth resistance of auxiliary earth spikes. Another feature, allows a simplified measurement by pressing the "Simplified Measurement" switch button only. No need to use a shorting wire as terminals P and C can be internally shorted by pressing this switch.

The model 4105 has many features such as a 2mA measuring current permits earth resistance tests without tripping earth leakage current breakers in the circuit under test.