Note: Descriptions are shown in the official language in which they were submitted.
WAVE~'ORM Ml'.ASUREMF.Nrl` ,r\ND DISPI,~Y APPARA'rUS
Background of the_Inven-tion
A waveform rneasuremerl-t and display appara-tus,
such as a transien-t recorder, waveform diyitizer, or a
digi-tal storage oscilloscope, receives one or more
analog electrical signals, converts such signals to
digital form and stores -them in waveform mernory for
subsequent retrieval and conversion back to analog
form for display. Because the signals are digitized
and storecl, various processing and display modes may
be implemented. For example, in a so--called pretrigger
mode, signal seqments which occur prior -to a trigger
event may be measured. Moreover, the stored waveforms
may be processed by a compu-ter -to provide mathernatical
analysis thereof. For measuring graphic (or character)
signals COrlSiSting of X (horizontal) and Y (vertical)
coordinates, or for measuring timing components or
phase relationships of two or more analog signals, an
X-Y display may be provided.
In the case of a conventional waveform measure--
ment apparatus which receives and digitizes two analog
input signals and stores the digitized signals in two
respective memory areas, the digital signals from the
two memory areas are subse~uently converted into ana--
log output signals, and then applied respectively to
the X-Y axes of a display device, such as a cathode-
ray tube, to provide the X-Y display. ~owever, it is
often difficult to discern the time relationship be-
tween the two input signals from only the X-Y display.
The conventional waveforrn measurement apparatus can
display the two input signals simultaneously in a Y-T
(wherein Y is amplitude and T is time) display mode so
that the time relationship of -the two input signals
may be analyzed. However, it is difficult to extrapo-
late a mental image of the X-Y display frorn the ~--T
3~
display of the two input signals. In addition, the
conventional waveform measurement apparatus has the
capability of expanding the Y-T display horizontally; that
is, the time axis of the ~-~ display can be expanded, but
is is difficult to discern the time relationship between
the expanded and unexpanded waveforms.
Summary of the Invention
In accordance with the present invention, a wavef~rm
measurement and display apparatus is provided in which the
foregoing disadvantages are overcome.
In accordance with an aspect of the invention there is
provided a waveform measurement and display apparatus
comprising means for receiving and processing first and
second electrical signals; means for selectively providing
a first display of at least one of said signals along a
time axis and a second display of said first signal along
a first axis with respect to said second signal along a
second axis normal to said first axis; and means for
producing time markers at corresponding time positions of
said first and second displays.
In a preferred embodiment, the apparatus comprises a
pair of signal-processing channels in addition to a sweep
generator arranged so as to provide both Y T and X-Y
display modes. In the Y-T display mode, either of the
pair of signal-processing channels may be selected to
coact with the sweep generator to provide a display, and
in the X-Y display mode, one of the signal-processing
channels may be selected to provide the X signal while the
other provides the Y signal. In addition, time markers in
the form of lines or intensified dots may be generated and
inserted into the same relative time positons of the
respective X-Y and Y~T displays so as to precisely
ascertain the time relationship between the two displays.
Furthermore, time markers may be inserted into the same
relative time positions for expanded and unexpanded
~2a-
waveforrns in the Y-~' display mode so as to precisely
ascertain the relative time position therebetween.
It is therefore one object of the present invention to
provide a novel waveform measurement and display apparatus
capable of discerning the time relat:ionship between an X-Y
display of two analog input signals and a Y-T display of
at least one of the two input signa3.s.
.
.
_3~
It is another object of the present Invention to
provide a waveform measurement and display appara-tus
in which the tirne relationship between expanded and un-
expanded waveforrns may be prec:isely ascer-tained.
Other objects, advantages, and fea-tures of the
present invention will become apparent to those having
ordinary skill in -the art upon a reading of the
following description when taken in conjunction with
the drawings.
Drawings
FIG. l is a block diagram of a preferred embodi-
ment in accordance wi-th the present invention;
FIG. 2 shows -the allotment of memory space for
the X-Y display random access memories of FIG. l;
FIG. 3 shows a typical dual-channel waveform dis-
play;
FIG. 4 shows a timing diagram for use in explain-
ing the operation of FIG. 1;
FIG. 5 shows a Y-T waveform display and an X-Y
display, both of which have -time markers inserted at
the same relative time position; and
FIG. 6 shows a display of expanded and unexpanded
waveforms each having time markers inserted into the
same relative time positions.
Detailed D scription of the Invention
Turning now to the drawings, there is shown in
FIG. 1 a block diagr~m of a preferred embodiment of a
dual-channel waveform measurement and display appa-
ratus in accordance with the present invention. An
analog signal at Channel 1 (C~ll) input terminal lO is
3~.~
"
applied throl~g`rl a pro~rarllmable at;tenuator 12 and a
buf`fer arnplifier 14 to ar) analog--to--digital converter
(AVC) 16. Simil.arly, an (3nalog signal at the C~12 i.nput
terrninal 18 is applied through a programmable attenu-
ator 20 and a buffer amplifler 22 to ADC 24. The
attenuation ratios of attenuators 12 and 20 are select-
able and are controlled by command signals from a main
bus 30, which includes data, address, and control
lines. Trigger circui.t 15 receives the outputs from
amplifi.ers 14 and 22 so that a -trigger point on either
of the two analog input signals may be de-tected.
Trigger circuit 15 rnay suitably include a prograrrlrnable
counter which starts to count a clock signal when the
trigger point is detec-ted~ and in accordance with
conventional practice a delay trigger (pretrigger) is
available. Trigger circui-t 15 receives trigger level
data and delay time data (for the internal program-
mable counter) from the bus 30, and in turn outputs a
trigger signal on bus 30. ADCs 16 and 24 convert the
analog input signals into 8-bit digital signals which
are applied to random-access memories (RAMs) 26 and
28, respectively. These RAMs may suitably be half-
areas of a single RAM. RAM 26 further receives data
and a write/read (W/R) control signal from bus 30, and
applies the 8-bit ou-tput to bus 30 and to a multi-
plexer (MUX) 32. RAM 28 further receives data and the
W/R control signal from bus 30, and applies the 8-bit
output to bus 30 and MUXs 32 and 34. Selection control
signals from bus 30 are applied to MUXs 32 and 34, and
the outputs therefrom are applied to digital-to-analog
converters (DACs) 36 and 38, respecti.vely. A surmning
circuit 40 adds the output from DAC 36 to the output
from DAC 42, which receives offse-t da-ta from bus 30,
and the output frorn surnmi.ng circuit 40 is applied
through push-pull output amplifier 44 to the Y-axis of
a display device such as the vertical deflection
plates of a cathode-ray tube (C~T) 46. The output frorn
DAC 38 is applied through a push-pull output amplifier
-5--
48 to the X-axis, such as the horizorltal deflection
pla-tes of CRT 46.
A 10-bit address counter 50 receives data from
bus 30 at the preset terminal thereof, and RAMs 26 and
28 receive a 10-bit address signal from either bus 30
or coun-ter 50. MUX 34 further receives the ou-tput frorn
10-bit counter 52 and two-bit data from bus 30. A
clock generator 54 generates clock signals, the fre-
quencies of which are de-termined in accordance with
data from bus 30. The clock signals are applied to the
counter portion of trigger circuit 15, ADCs 16 and 24,
counters 50 and 52, and Z-axis amplifier 56, the
output of which is applied to the grid of CRT 46. A
central processing unit (CPU) 58 which may suitably be
a microprocessor, is connected to bus 30 along with a
CPU RAM 60, read-only memory (ROM) 62 and a keyboard
64. RAM 60 is used as a temporary memory for CPU 58,
and ROM 62 stores firmware for controlling CPU 58.
Ke,vboard 64 controls the selectable attenuation ratios
of attenuators 12 and 20, the trigger level and posi-
tion of trigger circuit 15, the clock frequency of
clock generator 54, the W/R mode of RAMs 26 and 28,
MUXs 32 and 34, etc., via CPU 58.
The operation of the apparatus of FIG. 1 is as
follows. In the writing mode, the user enters into the
keyboard 64 the deslred attenuation ratios of attenu-
ators 12 and 20, the trigger level and position of
trigger circuit 15 and frequency of clock generator
54. In execution, RAMs 26 and 28 receive a write
command signal f'rom bus 30. The analog input signals
at terminals 10 and 18 are attenuated to proper ampli-
tudes and applied to buffer amplifiers 14 and 22. ADCs
16 and 24 convert the analog outputs from amplifiers
14 and 22 into respec-tive 8-bit digital signals, and
the conversion speeds of these ADCs are determined by
the cloclc frequency from cloclc generator 54. Counter
-6-
courlts the clock signal -to produce a sequential
address signal. It should be note~ that the clock
signal to counter 50 is synchronized with the clock
signal to ADCs 16 and 2~,. RAMs 26 and 28 store the
8-bit digital ou-tputs from ADCs 16 and 24, respec-
tively, in accordance with the address signal from
counter 50. FIG. 2 shows memory maps for RAMs 26 and
28, and as can be seen, the memory space includes
memory areas W for waveforms (the outputs frorn ADCs 16
and 24), areas CU for cursors and areas CH for char-
acters. It should be noted that the outputs from ADCs
16 and 2~ are stored in memory areas W of RAMs 26 and
28. Memory areas CH store the character inforrnation
from bus 30, and such character information indicates
in alphanumeric form the setting conditions such as
the attenuation ratios, the clock frequency (time per
division) or the like.
When the display mode is selected, CPU 58 applies
the read control signal to RAMs 26 and 28 via bus 30.
In the ~-T display mode, MUX 34 selects the output
from counter 52, which counts the clock signal from
clock generator 54 to produce a 10-bit digital signal.
DAC 38 converts this digital signal into an analog
signal to produce a ramp signal to drive the horizon-
tal sweep. In other words, the combination of counter
52 and DAC 38 comprises a sweep generator. During a
first cycle of the sweep signal, MUX 32 selects RAM
26. During a second cyc]e of the sweep signal, MUX 32
selects the output from R~ 28. The output digital
signal from MUX 32 is converted into an analog signal
by DAC 36, and applied to CRT 46 through summing
circuit 40 and output amplifier 44. DAC 42 generates
an offset signal in response to the command from bus
30 so that the waveforrns stored in RAMs 26 and 28 are
displayecl at different vertical positions on the
screen of CRT 46 as shown in FIG. 3. In FIG. 3, C}ll
and C~12 indicate the waveforms stored in RAMs 26 and
--7--
28, respectively, and any charact,er inforrnation is not
shown because it is not germane to this discussion.
The abo~e operations are controlled in accordance with
CPU 58 and -the firmware stored in ROM 62.
In the X-Y display mode, MUX 32 selects RAM 26
and MUX 34 selects RAM 28; that is, the waveform
stored in RAM 28 becornes the X-axis signal and the
waveform stored in RAM 26 becomes the Y-axis signal.
DAC 42 generates the offset signal in thi,s mode.
When the apparatus user wishes to discern the
time relationship between the X-Y display and the Y-T
display, both the Y-T and X-Y displays and cursors
(markers) are displayed simultaneously as will be
seen. The user selects the cursor point via keyboard
64, and the 10-bit address signal (corresponding to a
point on the time axis of the waveform) of the cursor
point is stored in RAM 60. The 8-bit data of RAM 26 at
the cursor poi,nt is transferred to the memory area CU
of RAM 26, and the 8-bit portion of the 10-bit cursor
address signal in RAM 60 is transferred to the memory
area CU of RAM 28 under control of CPU 58. It should
be noted that the memory area CU may be one word
(8-bit) capacity.
FIG. 4 is a time chart illustrating the X-axis
and Y-axis signals applied to output amplifiers 44 and
~8. At time to~ MUXs 32 and 34 select the outputs of
RAMs 26 and 28, respectively. Memory area W of RAM 26
is addressed in sequence to read out the stored signal
representations, and counter 52 counts the clock sig-
nal to produce the sweep signal as discussed herein-
above, so that the Y-T display of the waveform in RAM
2~ (CHl) is displayed on the screen of CRT 46 as shown
in FIG. 5. A period between times tl and t2 is a rest
period for the next step. At time t2, address counter
50 addresses memory areas CU of RAr~s 26 and 28, and
MUX 3~. selects RAM 28 and bus 30. 'I`hus, OAC 36
receives -the waveform da-ta at the cursor point, and
DAC 38 receives -the 8-bit portion of the 10-bit c~rsor
address signal from RAM 28 and -the other two-bit
portion from RAM 60 through bus 30. DACs 36 and 38
generate the cursor informat-ion during the period be-
tween times t2 and t3, and the electron beam bombards
the same position o-f the screen of CRT 46 -to indicate
cursor 66 wi-th intensity modula-tion. Thus cursor 66
appears as an intensified dot on the waveform display.
The period be-tween times t3 and -t4 is a rest period
for the nex-t s-tep. The characters stored in memory
areas CH of RAMs 26 and 28 may be displayed as well;
however, -this operation is omitted in this description
because it is not germane to the invention.
At time t4, address counter 50 starts to address
memory areas W of RAMs 26 and 28 in sequence in order
to provide an X-Y display on the screen of CRT 46 as
shown in FIG. 5. As described earlier, -the waveforms
in RAMs 26 and 28 are the Y-axis and X-axis signals re-
spectively. DAC 42 applies an offset signal to summing
circuit 40 in order -to control the vertical position
of the X-Y display. Thus the contents of memory areas
W of RAMs 26 and 28 are read out between times t4 and
t5, and at time t5 the rest period starts for the next
step. At time t6, CPU 58 presets address counter 50 in
accordance with the cursor address signal in RAM 60
and counter 50 addresses the cursor point in memory
areas W of RAMs 26 and 28. DACs 36 and 38 generate
cursor information during the period between times t6
and -t7 and the electron beam borrlbards the same posi-
tion of the screen of CRT 46 to indicate cursor 68
with intensity modulation. It should be noted that
cursor 66 and 68 indicate -the same rela-tive time
position of the Y-T display of -the signal in Channel 1
in this instance, and the X-Y display of the signals
of Channels 1 and 2. The above operations are con-
3~=3
-9-
trol~Led In accordance with CPU 58 and the firrrlware i.n
~OM 62. If the user changes the cursor to another
position via keyboard 6~, the cursor address signal in
RAM 60 is rewritten and the above operations repea-t.
s
FIG. 6 illustrates the screen of CRT 46 in the
horizontal magnification mode. In this instance, RAM
26 has stored therein a digi-tized triangle waveform.
Unmagnified waveform 70 and cursor 72 are displayed in
the same rnanner as described for -the Y-T display. In
order to display magnified waveform 74, the clock
si.gnal from clock generator 54 is changed -to a higher
frequency signal in response to the command from bus
30. The magnification ratio is determined by the ratio
of the read out clock frequency of waveforms 70 and
74. Cursor 76 is displayed in the same manner de-
scribed earlier. It should be no-ted that the timing of
cursor 76 corresponds to that of cursor 72. Cursor 72
may be moved along the waveform in accordance with a
cursor command from keyboard 64; however, cursor 76 is
stable at the predetermined horizontal posi-tion while
waveform 74 moves horizontally in accordance with the
cursor command because the starting address of counter
50 is preset by CPU 58 in accordance with the cursor
position for waveform 74.
As understood from the foregoing description, the
waveform measurement apparatus of the present inven-
tion is capable of di.splaying both the X-Y display of
two input signals and the Y--T display of at leas-t one
of the two input signals against an internally gener-
ated sweep. Moreover, time markers may be inserted
into the same relative time positions of the X-Y and
Y-T displays, so that it is easy to discern the time
relationship between the X-Y and Y-T displays. The
apparatus in accordance with the present invention can
also precisely ascertain the time relationship between
the hori~ontally magni.fied and unmagnified waveforMs
- ~ o -
in the Y--T display mode. rrhese operations are con-
troll.ed by CPU 58 and the firrmware i.n ROM 62.
While -the foregoing description pertains to a pre-
ferred ernbodiment of the present invention, it w:ill be
apparent to -those having ordinary skill in the art
that various rnodifications may be made wi-thout depart-
i.ng from -the scope and spirit of the present inven-
tion. For exarnple, while the time markers are dis-
cussed in terms of intensi-ty rnodulated dots, such -time
markers may also be a cursor line or a spike. These
-types of markers may be generated in accordance with
well-known -techniques.
