5 Difference between voltage and current measurements.
Fig. 2-A is a standardvoltage
measurement,
where the
potential difference between 2 points is checked, for
which the meter is connected in parallel with load, while
-B checks
the current supplied
by power andconsumed
by load, where the meter is connected
in series
with the
circuit. Basically,
the differenceis whether the meter is
connected in parallel or in series
with ioad. The latter
connection accompanies
the trouble of cutiing openthe
circuit beingchecked.
Itflu
It)tu
EP
Zn+o
Fig.2
In respect of measurement loss, the bigger the im-
pedance
of the meter(Zu) is, the smaller
is the current
(Iu) required for measurement
for the former, and, on
the contrary, the smaller
the impedance
of the meteris,
the voltage loss (drop) by IrxZu. (Ir - cunent
consumption) Thus, high accuracydata
areobtained by
the YX-360TR becauseof its very small current loss of
50uA for DCV and l25uA for ACV measurements
at
full scale, the voltage drop for current measurement
being250mV.
6 Voltagemeasurement
and internalimpedance.
There are 2 instances
of voltage
measurement
by parallel
connection. In caseof Fig. 2-A, there exists no high
impedance
corresponding
to Re of Fig. 3. Power
supply
sourcehas
its own internalresistance,
but it issosmall
as
can be ignoredfor voltagemeasurement,
and the loss
of
current consumption by a tester is practically nil the
meter reading
Ep. But, as can be noted in Fig.3, the
circuit condition changeson account of R4 present
and
200kQ of the tester connected
in parallel
for measure-
ment. Consequently, the
meter reads 3.77V against
the actual 4V resulting in
some
error.Therefore,when
measuring such a circuit,
where R is usuallyreplaced
with a tube or a transistor,
the circuit impedanceand
internal resistance of the
YX 36!TR I'VRANG'
R,=l0iV X20kl=lSki it
mk!
E.
Fig. 3
voltage range of the tester used for. measurement
must be referred to each other in reading the data
obtained.
In Fig. 3, the circuit impedance
is
about l/10
of the impedance of the tester, and reading error of
within -5% can be ignored, though the bigger the
internal
impedance
of a tester,
the better.
The high impedance
of 20kCl/V for DCV and 8kC2/Vfor
DCV of this instrument displays its full ability in the
voltagemeasurement
of highimpedance
voltage
amplify-
ing circuit, AVC, AGC and transistor bias circuit to
obtain high accuracy
data.
h'Zu ( Ep
-10- - ll -
