Tektronix 212 User manual

COMMITTED TO EXCELLENCE
OPERATORS MANUAL
First Printing NOV 1972
Revised 1981
Re-Typeset NOV 2021
212
OSCILLOSCOPE

TABLE OF CONTENTS
Page
Introduction 1
Safety Considerations 1
Controls and Connectors 1
Operating Power Information 6
General Operating Information 11
Operator’s Adjustments 21
Applications 24
Copyright © 1972 Tektronix, Inc. All rights reserved.
Contents of this publication may not be reproduced in any form
without the written permission of Tektronix. Inc.
Products of Tektronix, Inc. and its subsidiaries are covered by U.S.
and foreign patents and/or pending patents.
TEKTRONIX, TEK, SCOPE-MOBILE, and are registered
trademarks of Tektronix, lnc. TELEQUIPMENT is a registered
trademark of Tektronix U.K. Limited.
Printed in U.S.A. Specification and price change privileges
are reserved.
Tektronix, Inc. • P. O. Box 500 • Beaverton, Oregon 97077
Typeset by Jared Cabot - 2021/11
070-1375-00 212 REV D MAR 1981 1172

212 OSCILLOSCOPE
INTRODUCTION
The 212 Oscilloscope is a dual-channel portable oscilloscope
using all solid state and integrated circuitry (except the CRT). The
small size of the 212 makes it an extremely portable oscilloscope
for on-location maintenance in many fields of application.
SAFETY CONSIDERATIONS
When battery operated, store the AC plug in the
insulated compartment. The RFI circuitry connected
between the instrument common and the AC power
plug can cause small amounts of current from an
elevated reference to be present on the AC power
plug, imposing a possible shock hazard.
CONTROLS AND CONNECTORS
Controls and connectors necessary for operation of the 212
(with the exception of the POWER (BATTERY) indicator on the front
panel) are located on the right side of the instrument. To make full
use of the capabilities of this instrument, the operator should be
familiar with the function and use of each control and connector. A
brief description of each control and connector, along with some of
the more important instrument specifications, are given here.
1
CAUTION
212 Operators Handbook

1. POWER (BATTERY) Indicator - red light (on front panel) to indicate
when the instrument is on. When light extinguishes, battery charge
is low and about 10 minutes of operating life remain.
2.
&
3.
VOLTS/DIV - selects vertical deflection factor (vertical VARiable
control must be in CAL position for indicated deflection).
Calibrated position accuracy within 5%.
Vertical system bandwidth;
1 mV/div, 100 kHz; 2 mV/div, 200 kHz; 5 mV/div, 400 kHz;
10 mV/div to 50 V/div, 500 kHz.
4.
&
5.
INPUT COUPLING - selects the method used to couple the channel
input signal to the vertical amplifier system.
AC - DC component of input signal is blocked. Low frequency limit
(-3 dB point) is approximately 2 Hz.
2212 Operators Handbook

GND - vertical amplifier input circuit is grounded. The applied input
signal is connected to ground through a large resistor to provide a
pre-charge path for the AC input coupling capacitor.
DC - all components of the input signal are passed to the vertical
amplifier system.
6.
&
7.
STEP ATTEN BALance - a screwdriver adjustment to balance the
vertical amplifier system for minimum trace shift when switching
deflection factors.
8.
&
9.
Vertical POSition - controls the vertical position of the appropriate
trace. OFF detent turns the channel off.
10.
&
11.
VOLTS/DIV VARiable - provides a continuously variable deflection
factor between the calibrated settings of the VOLTS/DIV switch for
the appropriate vertical channel. Extends the maximum deflection
factor to at least 125 volts/div.
12. VERTical GAIN - screwdriver adjustment to set the gain of the
vertical amplifier system.
13. AUTO PRESET - screwdriver adjustment to set the AUTO PRESET
trigger point for automatic trigger operation.
14. Trigger SOURCE - selects the source of the trigger signal.
COMP - the sweep is triggered from a DC coupled sample of the
vertical deflection signal after the vertical switching.
CH 2 - the sweep is triggered from an AC coupled sample of the
vertical deflection signal before the vertical switching and only from
Channel 2.
EXT - the sweep is triggered from the DC coupled signal applied to
the EXT TRIG banana jack.
3212 Operators Handbook

15. LEVEL/SLOPE - selects the amplitude point and the slope of a
trigger signal on which the sweep is triggered. When the indicator
dot is to the left of center, the sweep is triggered on the positive-
going slope of the trigger signal; to the right of center, on the
negative-going slope. When the LEVEL/SLOPE control is set to the
AUTO PRESET detent, the sweep is automatically triggered at a
preset level on the positive-going slope. Stable triggering requires
a minimum of 0.2 division internal signal or 1.0 volt external signal
amplitude.
16. INTENSITY - controls brightness of CRT display.
4212 Operators Handbook

17. SWP CAL - screwdriver adjustment to provide calibrated sweep
timing.
18. POWER - controls power to the instrument. Does not interrupt
charging current to the internal batteries when the instrument is
connected to an AC line voltage.
19. FOCUS - screwdriver adjustment to obtain a well-defined display.
20. HORIZ MAG - provides continuously variable sweep magnification
to a minimum of approximately five times the sweep rate indicated
by the SEC/DIV switch.
21. HORIZontal GAIN - screwdriver adjustment to set the basic gain of
the horizontal amplifier system.
22. Horizontal POSition - controls the horizontal position of the trace.
23. SEC/DIV - selects horizontal sweep rate (horizontal VAR must be in
CAL position for indicated sweep rate). Calibrated sweep rate
accuracy within 5%.-X-Y position allows for X-Y operation with CH 2
supplying the vertical deflection and CH1 the horizontal deflection.
24. EXT TRIG - banana jack for input of an external trigger signal.
25. COMMON - banana jack to establish common ground between the
212 and the external signal source or equipment under test.
5212 Operators Handbook

OPERATING POWER INFORMATION
Internal Battery Operation
The 212 is designed primarily for operation from the internal
rechargeable batteries. The operating time provided from the
internal batteries depends upon trace intensity, and battery charge
and discharge temperature. Typical operating time from fully
charged batteries at maximum trace intensity when charged and
operated at +20°C to +30°C (+68°F to +86°F) is 4.5 hours. Longest
operating time is provided at lower trace intensity.
The POWER (BATTERY) indicator provides an indication of the
operating power. When the light extinguishes not more than 10
minutes of instrument operating power remains. The 212
possesses an automatic battery protection circuit to prevent
excessive discharge and the resulting battery damage if the
instrument is operated below the battery charge level of
approximately 10 volts.
Battery Charging
The charging characteristics of the nickel-cadmium (Ni-Cd) cells
used in the 212 vary with the temperature at which they are
charged. Batteries charged at about +20°C to +30°C (+68°F to
+86°F) will deliver more energy than when the same batteries are
charged at a higher or lower temperature.
6212 Operators Handbook

To charge the batteries, connect the instrument to an AC line
and set the POWER switch to the OFF position. Allow at least 16
hours for the batteries to reach full charge. For longest operating
life of the batteries, increase the charge time of the instrument to at
least 24 hours once a month. This procedure balances the charge
on all the cells in the battery and reduces the possibility of any
individual cell becoming reverse charged.
The nickel-cadmium cells will self-discharge when the
instrument is stored and not used for extended periods of time. The
rate at which this self-discharge occurs is dependent upon the
storage temperature and humidity. If the 212 is to be stored for
extended periods, particularly at either high ambient temperature or
high humidity, it is recommended that the batteries be run through a
full charge cycle (16 hours) about every two weeks, or that the
instrument be left connected to the AC line.
Typical Charge Capacity (reference to charge/discharge at
+20°C to +30°C):
CHARGE
TEMPERATURE
OPERATING TEMPERATURE
-15oC
(+5oF)
+20oC to +30oC
(+68oF to +86oF)
+55oC
(+131oF)
0oC (+32oF) 40% 60% 50%
+20oC to +30oC
(+68oF to +86oF) 65% 100% 85%
40oC (+104oF) 40% 65% 55%
7212 Operators Handbook

AC Operation
Due to the capacitive line input circuit, sudden voltage
changes may cause damaging input current transients. Avoid
operating this instrument from square-wave inverter supplies,
or other sources that produce large voltage transients.
If the internal batteries of the 212 become discharged to the
minimum operating level, continued operation can be obtained by
connecting the instrument to an AC power source. Due to the
circuitry connected with the internal battery charger, the AC power
line voltage must be at least 110 volts for operation in this manner.
Also, when operated with fully-charged batteries from an AC line
below about 110 volts and at a maximum trace intensity, the internal
batteries discharge slowly. Approximately 36 hours of continuous
operation can be obtained with fully charged batteries at maximum
intensity and a 104-volt line. The internal batteries cannot be
recharged while the instrument is being operated from the AC line.
If the instrument is to be operated on a power line other than
110 to 126 V AC, 58 to 62 Hz, refer to Option Information.
8
CAUTION
212 Operators Handbook

TABLE 1
AC Power Source Information
212 Power Supply Voltage Range Frequency
Standard 110 to 126 VAC 58 to 62 Hz
Option 1 220 to 250 VAC 48 to 52 Hz
Option 2 90 to 110 VAC 48 to 52 Hz
Operating Temperature
The 212 can be operated from the batteries in ambient air
temperatures between -15°C and +55°C (+5°F and +131°F). The
instrument should only be connected to an AC line source in
ambient temperatures between 0°C and +40°C (+32°F and +104°F).
9212 Operators Handbook

Option Information
Your instrument may be equipped with one or more options.
This section describes those options or directs the reader to where
the option is documented.
Option 1
Option 1 equips the 212 for operation from a 220 to 250 VAC,
48 to 52 Hz power line source. A power cord cable assembly, for
adapting to appropriate power plugs, is included with Option 1
instruments. Refer to the 212 Service manual for additional
information concerning Option 1.
Option 2
Option 2 equips the 212 for operation from a 90 to 110 VAC, 48
to 52 Hz power line source. Refer to the 212 Service manual for
additional information concerning Option 2.
10 212 Operators Handbook

GENERAL OPERATING INFORMATION
Intensity Control
The INTENSITY control determines the brightness of the display
presented on the CRT. Since the brightness of the CRT display
affects the amount of current drained from the batteries, the
INTENSITY control should be set to the minimum usable level. This
will allow maximum operating time from the internal batteries. The
setting of the INTENSITY control may affect the correct focus of the
display; therefore, a slight re-adjustment of the FOCUS may be
necessary when the intensity level is changed. To protect the CRT
phosphor, do not turn the INTENSITY control higher than is
necessary to provide a satisfactory display. Be careful that the
INTENSITY control is not set too high when changing the SEC/DIV
switch from a fast to a slow sweep rate.
11212 Operators Handbook

Graticule
The graticule of the 212 is internally marked on the faceplate of
the CRT to provide accurate, no-parallax measurements. The
graticule is marked with six vertical and 10 horizontal divisions.
Each major division is segmented into five minor divisions at the
center vertical and horizontal lines. The vertical gain and the
horizontal timing are calibrated to the graticule so accurate
measurement can be made from the CRT display.
Vertical Deflection Factor
The amount of vertical deflection produced by a signal applied
to one of the vertical channels is determined by the signal amplitude
and the setting of the appropriate VOLTS/DIV switch and its VAR
control. The calibrated deflection factors indicated by the
VOLTS/DIV switch apply only when the VOLTS/DIV VAR control is
set to the CAL detent.
The VOLTS/DIV VAR control provides continuously variable
(uncalibrated) vertical deflection factors between the calibrated
settings of the VOLTS/DIV switch. The VOLTS/DIV VAR control
extends the maximum vertical deflection factor to at least 125
volts/division (in the 50 volts position).
12 212 Operators Handbook

Signal Connections
Two high-impedance signal probes are internally attached to the
212. These probes provide a one-megohm input impedance and a
shielded input cable to prevent pickup of electrostatic interference.
Without the use of a probe attenuator, the vertical deflection factors
can be read directly from the appropriate VOL TS/DIV switch.
Signals can be connected to the EXT TRIG banana jack with
short unshielded leads under most conditions. Be sure to establish
a common ground between the 212 and the equipment under test.
Attempt to position the unshielded leads away from any source of
interference to avoid errors in triggering. If interference is excessive
with unshielded leads, use a coaxial cable with a suitable adapter.
13212 Operators Handbook

Ground Considerations
Reliable signal measurements cannot be made unless both the
oscilloscope and the unit under test are connected together by a
common reference (ground) lead in addition to the signal lead or
probes. The ground straps on the attached probes provide the best
ground. Also, a ground lead can be connected to the-212 chassis
COMMON banana jack to establish a common ground with the
signal source.
Input Coupling
The INPUT COUPLING switches allow a choice of the coupling
method for the applied signals. The type of display desired and the
applied signal will determine the coupling method to use.
In the AC coupling position, the DC component of the signal is
blocked by a capacitor in the input circuit. The low-frequency
response in the AC position is about two hertz (-3 dB point).
Therefore, some low-frequency attenuation can be expected near
this frequency limit. Attenuation in the form of waveform tilt will also
appear in square waves which have low-frequency components.
The AC coupling position provides the best display of signals with a
DC component which is much larger than the AC component.
14 212 Operators Handbook

The GND position provides a ground reference at the input of
the appropriate vertical channel without the need to externally
ground the probe. The signal applied to the probe is internally
disconnected from the input circuit and connected to ground through
a one-megohm resistor. The input to the vertical amplifier is held at
ground potential.
The DC coupling position can be used for most applications.
This position allows measurements of the DC component of a
signal, and must be used to display signals below about 10 hertz as
they will be attenuated in the AC position.
15212 Operators Handbook

Pre-Charging
The GND position can be used to precharge the input coupling
capacitor of the channel to the average voltage level of the signal
applied to the probe.
The following procedure should be used whenever one of the
probe tips is connected to a signal source having a different DC
level than that which was previously applied.
1. Before connecting the probe to a signal source with a large
DC component, set the INPUT COUPLING switch to GND.
2. Connect the probe tip to ground to allow the input coupling
capacitor to fully discharge. Then, connect the probe to the
signal source.
3. Wait several seconds for the input coupling capacitor to
charge.
4. Set the INPUT COUPLING switch to AC. The display will
remain on the screen so the AC component of the signal can
be measured in the normal manner.
16 212 Operators Handbook

Trigger Source
The Trigger SOURCE switch allows for selectivity in determining
the source to trigger the sweep. For most applications, the sweep
can be triggered internally. In the COMP position, the trigger signal
is obtained from the vertical deflection system after the vertical
switching has occurred. Therefore, in the dual-trace mode of
operation, the display will be triggered on the chopping signal and
not necessarily on the selected slope of the LEVEL/SLOPE control.
In this position the 212 will trigger on at least 0.2 division of the
applied signal within the bandwidth limits of the instrument.
In the CH 2 position of the Trigger SOURCE switch, the trigger
signal is again obtained internally, but is selected before the vertical
switching and only from CH 2 of the vertical deflection system, on at
least 0.2 division of the applied capacitively coupled signal. In the
dual-trace mode, if the displayed signals are time related, both
channels can be triggered on the selected slope with the Trigger
SOURCE switch in this position. However, it is not necessary for
the CH 2 POSition control to be out of the OFF detent for a trigger
to be present in the CH 2 position.
17212 Operators Handbook

An external signal connected to the EXT TRIG jack can be used
to trigger the sweep in the EXT position of the Trigger SOURCE
switch. The external signal must be time-related to the displayed
signals in order to obtain a stable display. An external trigger signal
of 1 volt to 20 volts can be used to provide a triggered display when
the internal signal is too low in amplitude for correct triggering, or
contains signal components on which it is desired not to trigger.
The external trigger signal is useful when signal tracing in
amplifiers, phase-shift networks, wave-shaping circuits, etc. The
signal from a single point in the circuit under test can be connected
to the EXT TRIG banana jack. Then the sweep is triggered by the
same signal at all times to allow amplitude, time relationship,
waveshape changes, or signals at various points in the circuit to be
examined without resetting the trigger controls.
Trigger Slope
The LEVEL/SLOPE control determines whether the trigger
circuit responds on the positive-going or negative going portion of
the trigger signal. When the indicator dot is to the left of center, the
trigger circuit responds on the positive-going portion of the triggering
waveform (notice the positive-going waveform on the left side of the
control). To the right of center, the trigger circuit responds to the
negative-going portion of the triggering waveform (notice the
negative-going waveform on the right side of the control). Since this
instrument does not have an internal delay line, the display might
not start on the selected slope, particularly when the displayed
waveforms have a high repetition rate.
18 212 Operators Handbook