Multiplexed digital recording system with simple interface between it and standard commercially available oscilloscopes was developed. System included: rapid set-up, minimum input cabling, low cost, display expansion capability, and portability

Dudenhoefer, J. E.

Harrold, J. L.

English

NASA Technical Reports Server

March 1973
	
.	 B73-10006 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service. Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office. NASA, Code KT, Washington, D.C. 20546. 
A REMOTE TEST PARAMETER PROFILE DISPLAY 
Multiplexed Analog Data
Phasing I	
Blanking
 
I 
Commercial 
Oscilloscopes 
Word Sync. Thumbwheel	 1
External 
Trigger No. 1 Z-Axis (Counter Switch	 I 
Block Sync.
	
Counter Comparator No. 1 j
kAxis  (Counter Reset) Scope 1 
External  
No I Z-Axis Thumbwheel	 lf Trigger 
Switch H I Comparator No. 2 •.	 ' Y-Axis 
 Scope 2 
I 
I
External
I 
I 
I 
Thumbwheel Z-Axis 
Switch H I f	 Ii. Q . I Comparator No. N ] I Trigger No. Nj I Y-Axis 
Sco pe 	 I
n
The Problem: 
To obtain a profile plot display of many analog test 
parameter values relative to each other and whose values 
vary with real time. The system must be capable of easy, 
rapid set-up; must use a minimum of input cabling; must 
be low cost; must be capable of being expanded to any 
number of displays; and must be portable.
The Solution: 
A multiplexed digital recording system with a simple 
interface between it and standard commercially available 
oscilloscopes. All of the digital data is routed through a 
single digital to analog (D/A) converter. The result is a 
serial presentation of analog data for consecutive channels 
in the multiplexer pattern. The D/A serial data are then 
input to the Y-axis of a commercially available oscillo-
scope.
(continued overleaf) 
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How It's Done: 
The digital recording system provides two control 
parameters, word sync, a pulse that occurs for each digital 
data word that is input to the D/A converter, and block 
sync, a pulse that occurs each time the multiplexer 
recycles to the beginning of the sampling order. These 
sync signals are used to remotely derive a block position 
count (see figure). The word sync and block sync are 
input to a binary coded decimal (BCD) counter. The 
block sync is used to reset the counter and the word sync 
is used to advance the counter. The BCD counter output 
is continuously compared with a block position selected 
on a set of remotely located thumbwheel switches. When 
the counter and switches compare, a signal is developed 
for externally triggering the X axis sweep of an oscillo-
scope trace. This permits the oscilloscope trace to begin at 
any selected position in the data block. 
The oscilloscope trace will begin to sweep and will 
display the D/A serial data beginning with the parameter 
selected by the block position on the thumbwheel 
switches. The number of parameters displayed is then 
controlled by the time base selector of the oscilloscope. 
The area of data which is to be graphically displayed 
may be located anywhere in the total data block; but, 
each parameter to be displayed must be located in 
consecutively sampled channels. 
The data that are displayed on the Y axis of the screen 
will be the consecutive analog data samples, starting with 
the parameter occurring at the selected block position. 
The analog data samples are provided by a D/A converter 
fed with all consecutive data words derived by the data 
acquisition system. 
A Z axis blanking and unblanking function is used to 
remove frequency response problems and level transitions 
between consecutive parameter samples. Only the true 
"steady" portions of the sampled data will be displayed. 
The "rising" portion of each sampled word can be 
blanked out. Current levels of displayed data will appear 
as discrete level segments or dots.
Notes: 
1. Any number of displays may be incorporated simply 
by adding one set of thumbwheel switches, one trigger 
generator, and one oscilloscope per display. The entire 
system of N displays requires only three coaxial inputs 
- "Multiplexed Analog Data," "Word Sync," and 
"Block Sync." Each display is completely independent 
of every other display. 
2. Commercially available bar graph display systems cost 
approximately $3000/display while the cost for this 
system runs $150/display with the cost of the first 
display at $1200. 
3. Documentation may be obtained from: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73.10006 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: J.L. Harrold and J.E. Dudenhoefer

Lewis Research Center

(LEW-11872)
0 
S 
B73-10006	 Category 02


A remote test parameter profile display

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