LEM Saturn 100 Plus, Руководство по эксплуатации, Страница: 49 / 329

Information for the tester
47
Computation of the short-circuit current (I
K
) is based by the equation I
K
=
the value of U
MAINS
corresponding to the selected nominal mains voltage
(110/127/220/230/380/400 V) or to the voltage actually measured (see Setting the
Voltage, section 3.9).
If a probe is used in position L-PE, the fault voltage (earth/ground connection
voltage), i.e. the voltage drop between the PE connection and the probe „SONDE”
with reference to the short-circuit current, can be measured and displayed.
Rotary Field Direction
Measurement is effected by evaluation of the zero passages (comparators in ADC,
microprocessor). The two phase voltages are measured simultaneously, the larger
being displayed as U
1-3
, the other as U
2-3
.
Low Resistance Measurement R, Continuity check
The first measurement is a check whether the input voltage is less than 3 V.
If this condition is met, measurement is started. The required switching operations
are performed by relays controlled by the processor.
The voltage source is the battery. The DC voltage and the current flowing across
the specimen are measured, processed by the processor and displayed as a
resistance value. The second resistance value R
2
is obtained from a pole change
of the measuring current with subsequent measurement.
Pressing the key
T
„ “will start the automatic continuity check without pole
changing of the measuring current. At <2 Ohm a signal will sound and the display
will indicate
„con“ . With external voltage, the signal will sound intermittently. All
other measurements remain the same.
In order to avoid any build-up of voltage surges at the switching relays by
inductances in the testing circuit, the switchover is not enabled until the measuring
current has died down.
This is why the measuring time is dependent on any inductance in the circuit and
may be up to 20 s.
Protective Wire Test
Touching the metal contact area in the key area initiates a high-resistance detection
of whether a dangerous (>50 V) contact voltage exists at the protective wire (PE). If
this is the case, „ PE " is displayed via the processor..
Measurement of Frequency
A zero-passage comparator in the ADC is used to measure the duration of a cycle
of the input signal, which is subsequently evaluated in the processor and displayed
as a frequency.
U
Netz
R
S