HT instruments M71 - Manual (Page 9)

M71
EN – 8
4.3. EARTH 2W:TWO-WIRE EARTH RESISTANCE MEASUREMENT
4.3.1. EARTH 2W- Zero setting of cables
CAUTION
The instrument can be used for voltage and current measurements on
installations with overvoltage category equal to CAT III 240V to earth and
maximum voltage of 415V between inputs. Do not connect the instrument to
installations whose voltages exceed the limits indicated in this manual.
Exceeding such limits may cause electric shock to the user and damage the
instrument.
CAUTION
The values for cable zeroing constants under modes EARTH-2W and EARTH-
3W are stored into separate and independent cells.
Fig. 2: Instrument’s wiring for zero setting of cables under mode EARTH-2W
1. Press the instrument's start key.
2. Select function EARTH 2W pressing the left arrow key.
3.
Connect the red cable, the blue cable and the green cable to the corresponding
instrument's input terminals. The instrument shall keep the same operating features
during all measurement stages. Any cable extension or replacement as well as
additional crocodiles may nullify previous zero setting so requiring to repeat such a
setting procedure before effecting further measurements.
4. Connect the crocodiles to the test leads.
5. Short-circuit the measuring cables' ends (see Fig. 2) paying attention that the
crocodiles' metal parts make proper contact to each other. To get a safe connection
one of the rods provided with the instrument can be used..