32
time, as shown in Figure 2-10.
2.3.6 Signal source resistance
There are two resistances available: 30
Ω
(default) and 100
Ω
.
In Figure 2-11, Ei: signal source voltage
Ei; Ri: signal source resistance; Zx: the
DUT, Vx is its voltage and Ix current.
Then, Vx=Ei
Zx/(Ri+Zx)
Ix= Vx/ Zx= Ei/(Ri+Zx)
When Zx<<Ri
，
Ix= Ei/ Ri
The level across the DUT and floating
Figure 2-11 Equivalent diagram of signal source output
current, are related to the instrument’s
level (refer to §2.2.3 Test signal level), signal source resistance, and the DUT’s
impedance.
When measuring some components that are sensitive to signal’s value, such as
magnetic-core inductor, ceramic capacitor. To compare consistency between
each other, signal should be approximate, when the instrument’s signal source
resistance should be well known.
2.3.7 Key lock
The default state is “OFF”, indicating the keys can be operated, and initialization
state is default.
To avoid operator’s improper operation, the instrument provides the function of
key lock. In this state, all the keys are invalid except unlock key ‘FUNCTIN”. And
the instrument can’t be enabled until the function of key lock is cancelled.
2.3.7.1 Entering key lock
1. The instrument is in the state of normal measurement.
2. Press the following keys in order: FUNCTION,
＜
,
∧
, FUNCTION. When
“7-Loc ON” is displayed, exit to the state of “MEASURE”. And the instrument has
been in the state of key lock.
When the instrument is in the state of key lock, all the keys are not available.
And if the instrument is turned off in the state of key lock, it will keep the state
when it’s turned on next time, and measurement state and setting parameters
as well.
2.3.7.2 Exiting key lock
When the instrument is in the state of key lock, press the following keys in order:
FUNCTION,
∧
, FUNCTION. And when “7-Loc OFF” is displayed, exit to the state
of “MEASUREMENT”. The instrument returns to normal state.