BK Precision 2120C, Instruction Manual, Page: 13 / 30

OPERATING INSTRUCTIONS
NOTE
All operating instructions in this chapter
apply equally to
all Models except for the
sections on “Delaye d Sweep Operation"
and “Component Test”, which apply only
to the Model s 2125 C & 2160C . Other
differences are noted when nec essary.
SAFETY PRECAUTIONS
WARNING
The following precautions must be ob-
served to help prevent electric shock.
1. When the oscilloscope is used to make measurements
in equipment that contains high voltage, there is al-
ways a certain amount of danger from electrical shock.
The person using the oscilloscope in such conditions
should be a qualified electronics technician or other-
wise trained and qualified to work in such circum-
stances. Observe the TEST INSTRUMENT SAFETY
recommendations listed on the inside front cover of
this manual.
2. Do not operate this oscilloscope with the case removed
unless you are a qualified service technician. High
voltage up to 2100 volts is present when the unit is
operating with the case removed.
3. The ground wire of the 3-wire ac power plug places
the chassis and housing of the oscilloscope at earth
ground. Use only a 3-wire outlet, and do not attempt
to defeat the ground wire connection or float the oscil-
loscope; to do so may pose a great safety hazard.
4. Special precautions are required to measure or observe
line voltage waveforms with any oscilloscope. Use the
following procedure:
a. Do not connect the ground clip of the probe to
either side of the line. The clip is already at earth
ground and touching it to the hot side of the line
may “weld” or “disintegrate” the probe tip and
cause possible injury, plus possible damage to the
scope or probe.
b. Insert the probe tip into one side of the line voltage
receptacle, then the other. One side of the recepta-
cle should be “hot” and produce the waveform. The
other side of the receptacle is the ac return and no
waveform should result.
EQUIPMENT PROTECTION
PRECAUTIONS
The following precautions will help avoid
damage to the oscilloscope.
1. Never allow a small spot of high brilliance to remain
stationary on the screen for more than a few seconds.
The screen may become permanently burned. A spot
will occur when the scope is set up for X
−
Y operation
and no signal is applied. Either reduce the intensity so
the spot is barely visible, apply signal, or switch back
to normal sweep operation. It is also advisable to use
low intensity with
AUTO triggering and no signal
applied for long periods. A high intensity trace at the
same position could cause a line to become perma-
nently burned onto the screen.
2. Do not obstruct the ventilating holes in the case, as this
will increase the scope’s internal temperature.
3. Excessive voltage applied to the input jacks may dam-
age the oscilloscope. The maximum ratings of the
inputs are as follows:
CH 1 and CH 2:
400 V dc + ac peak.
EXT TRIG:
300 V dc + ac peak.
Z-AXIS INPUT (Model 2125 C & 2160C ):
30 V ( dc and ac peak).
4. Always connect a cable from the ground terminal of
the oscilloscope to the chassis of the equipment under
test. Without this precaution, the entire current for the
equipment under test may be drawn through the probe
clip leads under certain circumstances. Such condi-
tions could also pose a safety hazard, which the ground
cable will prevent.
5. The probe ground clips are at oscilloscope and earth
ground and should be connected only to the earth
ground or isolated common of the equipment under
test. To measure with respect to any point other than
the common, use CH 2 – CH 1 subtract operation
(
ADD mode and INV 1 ), with the channel 2 probe to
the point of measurement and the channel 1 probe to
the point of reference. Use this method even if the
reference point is a dc voltage with no signal.
11
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