Simulating operation of thermopile vacuum gage tube at high and low pressure

Yeager, P. R.

English

NASA Technical Reports Server

RiPLY TO 
ATTN OF: Gp 
TO: 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
November @, 1970 
u s ~ / ~ c i e n t i f  ic & Technical Information Diviaion 
hltentiont tcrius Winnie M, Morgan 
FROM t ~~/0ffice of Assiqtaqt General Counsel for 
Patent Matters 
SUBJECT: ~ n n o ~ c e m e n t  of NASA-Owned U. 6. Patents in STAR 
In accordance with the procedures agreed upon by Code GP 
and' Code USI, the attached NASA-oumed U. S, Patent is being 
foxwarded for abstracting and announcement i n  NASA STAR. 
. 
, - 
The fol laving information is provideds 
U. S .  Patent No, 
Government or 
Corporate Employee 
Supplementary Corporate 
Source (if applicable) 
.. --~ 
N S A  Patent Case No. vrdLA -,& 758 - 
https://ntrs.nasa.gov/search.jsp?R=19710009006 2020-03-17T02:48:23+00:00Z
P, W+ VEACER - B  2 53 1,978 
TI3ERMDFILE VACUUM GAS:: 'T:IBE SIEriLJLATOR 
F i l e d  Sept. 13, 1968 
FIG.  I 
INLJEN? OX, 
PAUL 9 VEAGER 
b Y 
United States Patent 06 5,531,938 '' Patmind Oct. 6, L37ii 
THERMOPILE T ~ ~ u u - M  GAGE TUBE 
SIMULATOR 
Paul W. Ueager. Grafton. Va.. assignor to the United 
States o f  A%rica as rebresented bi the Administrator i: 
of  the National Aeronabtics and $pace Administration " 
Filed Sept. 13, 1968, Ser. No. 759,665 
Int. CI. GO11 27/00 
U.S. Cl. 73-4 4 Claims 
ABSTRACT OF THE DISCLOSURE 
A device for simulating the actions of a thermopile 
vacuum gage tube a t  high and low pressures. A battery 
in series with a first resistor simulates the voltage gener- 15 
ated by the gage tube when operating a t  atmospheric 
pressure, and the battery in series with a second resistor 
sin>ulates the voltage generated by the gage tnbe while 
exposed to a vacuum. Three other equal resistors are con- 
nected together a t  a common junction to  sinlulate the 20 
resistances of the thermocouples in the gage tube. The de- 
vice is used to check out thermopile vacuum gage circuits. 
The invention described herein was made by an em- 25 
ployee of the United States Government and may be 
manufactured and used by or  for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
The invention relates generally to a device for simulat- 30 
ing the actions of an  electrical element and more spe- 
cifically concerns a device for simulating the actions of 
a thermopi!e vacuum gage tube a t  high and low pressure. 
Prior t o  this invention, thermopile vacuum gage cir- 
cuits were checked out by connecting an actual thern~o- 25 
pile gage tube in the circuit and pulling a vacuum on  the 
gage tube to obtain a low pressure reading, and opening 
the gage tube to atmosphere to obtain a high pressure 
reading. The disadvantages of this prior method of check- 
ing out thermopile vacuum gage circuits were the re- 40 
quirement to have a vacuum system, the long time re- 
quired to pump the vacuum system down to a low pres- 
sure, the possibility of damaging a relatively expensive 
vacuum gage tube, and in the case of wind tunnel use, 
the problem of actually connecting the thermopile vacuum 45 
gage tube to the vacuum. 
I t  is therefore an  object of this invention to decrease 
the disadvantages of the prior method of checking out 
thermopile vacuum page circuits. 
Another object of this invention is to provide a device 50 
for simulating the actions of a thermopile vacuum gage 
tube at  high and low pressures that can be used to check 
out thermopile vacuum gage circuits. 
Other objects and advantages of this invention wil! be- 
come apparent hereinafter and in the drawings in which: 55 
FIG. 1 is a thermopile vacuum gage circuit connected 
to a thermopile gage tube for the purpose of showing 
how thermopile vacuum gage circuits were checked out 
prior to this invention; and 
FIG. 2 is a schematic di'siliing of the invention. GO 
Turning now to FIG. 1 the. number 11 designates a 
thermopile vacuirm gage and the nilnlber 12 designates a 
tlrei.n.iopilc v;icrrurn gage circuit. Gage 11 consist? of t h w c  
thermocotiples, 13, I4 and 15, inside an  enclosure I d .  
An opening 1-s provided for allowing the pressure in 65 
the space inside enclosure 16 to be lowered. Thermo- 
couples 13, 14. and 15 are connected to terminals 118, 
19 and 20, respectively. Circuit 12 consists of a trans- 
former 21, a potentiometer 22 connected across the sec- 
ondary of the transformer and a voltmeter 23, calibrated 70 
to read pressure, connected to the slider of potentiometer 
22. In operation of the prior art device in FIG. 1, the 
space inside enclosure 16 is exposed to the atillospllere 
tilroirgh opening 17. Then ihc slider- of poteniionlcter 22 
is adjusted until voltmeter 23 indicates the correct read- 
ing for atmospheric pressure. In this condition FIG. 1 
is a slightly unbalanced Wheatstone bridge with the two 
sides of potentiometer 22 and thermocouples 13 and 14 
being its four legs. Then gage 1 1 is exposed to the vacuum 
to be measured through opening 17. The resulting change 
in pressure inside enclosure 16 causes the Wheatstone 
bridge to become more unbalanced. The unbalanced volt- 
age is measured by meter 23 which is indicative of the 
pressure of the vacuum. 
When a device as shown in FIG.  1 is used to measure 
the pressure of partial vacuums the thermopile vacuum 
gage circuit should be checked out t o  insure that it is 
operating properly. In  the past this has been done by 
connecting circuit 12 to gage 11, as shown in FIG. 1, 
pulling a vacuum on the gage tube to obtain a low pres- 
sure reading, and opening the gage tube to atmosphere 
to obtain a high pressure reading. 
Referring now to FIG. 2 there is shown a device for 
simulating the actions of thermopile vacuum gage 11 
which can be used in place of gage 11 to check out cir- 
cuit 12. Resistors 25, 26 and 27, nominal value of 10 
ohms, but which may be varried for exact match, simu- 
late the resistances of thermocoup!cs 13, 14 and 15, re- 
spectively, so that proper current drain from the gage 
circuit will occur. A resistor 28, nominal value of 15,000 
ohms but which may be varied for exact match, is con- 
nected to a single pole, double throw, center-off switch 39 
which is connected to a battery 30, nominal value 1.5 
volts. When switch 29 is in the position shown the current 
that flows through resistor 28 due to battery 30 generates 
a voltage drop in the circuit that sin~ulates the voltage 
generated by thermopile vacuum gage tube 11 when oper- 
ating at  atmospheric pressure. A resistor 31, having a 
nominal va!ue of 1000 ohms, also is connected to switch 
31. When resistor 31 is connected in the circuit with 
battery 30 the resulting current through resistor 31 gener- 
ates a voltage drop in the circuit that si~~lulates the volt- 
age generated by thermopile vacuum gage tube 11 while 
exposed to a vacuum. Terminals 32, 33, and 34 are means 
for connecting the simulator to thermopile vacuum gage 
circuit 12. 
In  operation the simulator in FIG. 2 is connected lo 
gage circuit 12. Switch 29 is put in its "off position and 
the slider of potentiometer 22 is adjusted until meter 23 
reads zero current. This insures that there will be no al- 
ternating curent passing through meter 23. Switch 29 
is then positioned as shown. The resulting voltage im- 
balance causes a current flow past terminal 33 and is 
measured by meter 23 which gives a reading approxi- 
mately equal to atmospheric pressure. Then switch 29 is 
positioned to connect resistor 31 in the circuit. The re- 
sulting reading on meter 23 is approximately equal to high 
vacuum. 1111proper functioning of gage circuit 11 or con- 
necting cables will result in readings on meter 23 different 
from those above. 
An advantage of this invention is that it permits the 
check out and troubleshooting of thermopile vacuum gage 
circl~iis by means of moving one switch instead of iiav- 
ing to colliiect ;i gage ttibe to ;I vacrllirm sq.stein. ar!d 
prrmp the system to a low pressr~re. Also, ir~corsccr elec- 
tricnl connections can damage w gage trthe, hut the in- 
vention is not easily daniaged, and if it is, is easily 
repaired, whereas the gage tube is not easily repaired. 
It is to be understood that the form of the invention 
herewith shown and described is to be taken as a pre- 
ferred embodiment. Various changes may be rilade in the 
shape, size and arrangement of parts. For example, 
equivalent elements may be substituted for those illus- 
trated and described herein, parts may be reversed and 
-% 'I?-. ; ; , , re)  r ,978 
1 
4 4. 
ceri:iir~ fci>!r!i-cs of !!,<: ir?veg!io~~ n!;iy ti:: rit i l i / t:t l  ir l i i i l-  leriirin1lIs are conilecicd ro :t ~hei-ii l~pilc v;hciiur?r f ~ l q c  
pendently of the rrse of otlrzr Ecairtres, all without depnrt- circuit said device can be uieii to siiiliiiate a fhern~o- 
iirg froill the spi!.it 01. vcnpe of the inve~ition as defncd in pile vacuLun gage tube at high and low pressures. 
the sttbjoined claims. 7'11e values of the resistors and bat- 2. A device for simulating the actions of a thern~opile 
tery used by this invention can be different from those _ vacuum gage tube according lo claim 1 wherein said 
specified. Even though this invention ha: been disclosed " switch has a third position for disconnecting said battery 
for checking out circuit 12 in FIG. 1, it is to be under- whereby when said switch is in its third position and 
stood that the invention could be used to  check out many said separate terminals are connected to a thermopile 
different types of tl~ermopile vacuum gage circuits in- vacuum gage circuit the resulting bridge circuit can be 
cluding transistor-oscillator power units. Resistors 25, 26 balanced to eliminate the current flowing through said 
and 2'7 may be variable to match the exact thermocouple first impedance. 
resistance to obtain more accurate simulation of an indi- 3. A device for simulating the actions of a thermo- 
vidual gage tube; and resistors 28 and 31 may be made pile vacuum gage tube according to claim I wherein said 
variable to exactly match the "atmosphere" and "high first, second, third, fourth and fifth impedances are 
vacuum" points on the meter read-out system. 15 resistors. 
What is claimed is: 4. A device for simulating the actions of a thermopile 
1. A device for simulating the actions of a thermopile vacuum gage tube a t  high and low pressures comprising: 
vacuum gage tube a t  high and low pressures to check out first, second and third impedances with one end of 
thermopile vacuum gage circuits comprising: each connected together such that each impedance is 
first, second, and third impedances with one e7:d of 20 connected to  the junction of the other two im- 
each connected together such that each impedance pedances and with the other end of each connected 
is connected to the junction of the other two im- to a separate terminal; and 
pedances and with the other end of each connected means connected in parallel with said first impedance 
to a separate terminal; for selectively generating voltages to simulate the 
a battery; 25 voltages generated by said thermopile vacuum gage 
a fourth impedance which when connected in series tube at high and low pressures whereby said separate 
with said battery simulates the action of a thermopile terminals can be connected to thermopile vacuum 
vacuum gage tube a t  high pressure; gage circuits to check them out. 
a fifth impedance which when connected in series with 
said battery simulates the action of a thermopile 30 References Cited 
vacuum gage tube a t  low pressure; and UNITED STATES PATENTS 
a switch having a t  least two positions for connecting 2,460,873 2/1949 Cleweli e t  al. ---------- 73-399 
said fourth impedance in series with said battery 2,$76,417 3/1959 Winram. 
with the resulting series circuit connected in parallel 3,397,579 $/I968 Harvey --------------- 73-399 
with said first impedance when it is in one position 35 
and for connecting said fifth in~pedance in series with S. CLEMENT SWISHER, Primary Examiner 
said battery with the resulting series circuit con- 
nected in parallel with said first impedance when it U.S. C1. X.R. 
is in its other position whereby when said separate 324-44 


Thermopile vacuum gage tube simulator Patent

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