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Construction and tests of a globe photometer
(USC Thesis Other)
Construction and tests of a globe photometer
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Content
COJ~TRUCTI A_D TESTS
OF
A GLOBE PHOTO A ETER
A Thesis
Presented to the
Depart ent of Electrical En ineering
University of Sout em California
ritten in partial fulfillment
for the de ree o
acnelor of Science
by
June 5, 1.,16
A roved by
J
/
-
CONTE}1TS
Chapter
Page
I. Experimental tests on various forms of
photometeree;••····· .•......................• 1
L. O. Grounda.hl's Statement •.•..............• 1
Wild
I
s Experiments • • • • . . . . . . . . . • . . . • . . . . . . . • • 2
L. O. Groundahl's FJCperiment •..........•. .. • 3
II. Constructior and Tests of U brich Sphere or
Gl\Jbe Photometer • . . . • . . . . . • • • . . . • . . . . . . . . . • 5
T eo ry of t1 e Sphere • • • • • . . . . . . . . . • . . • • • • . . . . 5
Bloch
I
s Experiment • • . • • • . . . . . . . . . . . . . . . . . . . . • 7
Method of Construction •••..... ..... .........• 8
'ethod of Calibration of Standard Lamp •.•. .. . 9
M ethod of Calibration of Sharp- ·illar Photo-
meter • • • • . . . • • . • . . . • . . . . • • . . • • • . • . . . • . . . • • 11
Calibration of Globe Photometer •...........• 12
Comp arative test s on Str et Lam Balls ....•. 14
CHAPTER I
Experimental Tests on Various Forms
of Photometers .
The recent development of the concentrated filament lamp,
and the necessity of rating lamps in lumens or means heric l
candle-power, rathe r t h n ~ean heni sp erical can le-power has
caused a study of the subject o! integratin pmtometere. A
large spherical photometer desi srned by Ul ric r. at resent
holds to the exclusion of all ot ere. Thie integrator as
some disadvantages, amot ic' is t e first cost, ue tote
difficulty in making a lar e spherical s rf ce. T i s to et r
with a number of statem ents in the liter ture t t e ef fect
that a box or any incloeure of any sha e w at eoever oul do
as well as a sphere, led to a serie of ex.erimente on boxes,
rectangular and ot erwise, in t he hoe th~t so th· oul be
found to replace the s phere.
L. O. Groundahl says, "In or er to corroborate e st te
mente of those who have sai th ta box may be uae inst ead of
a sphere to compare sources of di f eren~ ietributio s ma es it
necessary to use a box th tis cubical, an its accur cy is still
further increased by eliminatir. t e corners, thus a r oachin a
sphere. Thie bein done t e proper precautio s bein ta en i
regard to the screen and in re a r d toted rk part of th uni ·
introduced the box yields sati sfactory results . en t e light
units all have the same distri t i on n re si il rly or iented
with reference tote dim ension oft e box, t e in~ rior h ve
l
undoubtedly any ehape."
1
Wild used for his ex eriment a box, the interior dime -
aions of wl ich were 22 x 20 x 20 inches (55.9 x 50 .8 x 5v. c ).
He tested the effect of li -·ht distribution by means o.t a tun -
sten lamp havin ~ a very small en on distribution. In his own
words he said, "Tests were made it various screens an id
ews., and with the lamp and screens in v rio s oeitions."
2
Some o! 1r. ~ild
1
a tests were as follo1s:-
1. "10 inch (25.4c 1) circular screenJ ire _ ee (20. 3o )
from t e back, cle' r i r- o • Test late sees fr nt
of screen only an no i .t fro t. 1 ,s falls i
reotly upon this side. Ap~arent C. P. 3 % . Greater
witl lamp filament _orizontal tan en vert ·cal.
2. Conditions same s above but ith w· dow covered ith
t hin blottin~ a~er in wax. Difference 2.5 ,
on chan in over.
3. Rectangul r scree 5 ir.c· s (12. 7cr ) b 3 ·n .es (7 .6
cm)~ 8 inches from fro t . Lamp 8 i c~ e from fro t •
Waxed blottin pa er in wino •
with filament horizont 1.
• 5 ~ m re emission
4. Conditions as above, but screen 6.5 inc, es fro fro t.
Same results.
5. 5" x 3" screen, 6.5 inches from front. 4
aion with filament oriz ntal.
less emis-
1
L. o. Groundahl, Transact~ons of ~I ....................... -... ........ - -------e ....... r~i_ng_ ocietY,,
arch 20, 1916. Vol XI
2
ild, Il_ luminati 1e; Engin_eer, Lon on ol I II, p. 549, 1911.
2
6. Sarne as above, l amp tilted 45° 2
ed."
less emission obtain-
Thus it appears t hat for t esting incandesc nt lamps a rectangu-
l ar box constructed i n acc or dance
. t ,
n t 1e above ex ri ent is
practicable., and i n pra ctice is no l i ely tor ult in a very
l ar ge error i f due precaution is taken .
M r. Groundahl'e fir st ex~eri ent as m e i h a box 42 x
33. 75 X 24 inche s., t he interio r o ich inte it 11th-
ophone .
A
st u y as m with t he i 0 '{
at ifferent places
in t he
. ..
s1.ae of t e box, but
"-~Ce
ir~ he s·de
was f o n ' t
...
e
2."
.----a ----rl
f
{
:: )
. r
.
o s t ~ on
"':- r a l 1
....
..
..
the l engt bo a l es to t at
•
posi-
•
c~~,.·ne; d the rea in about
4 / I
t t
a long the
ion
as kept in the f ormer positi n n
r t he mi~
le of
the box t he readin s see· ed very co .LSi tent .
---"'
~
--
,o
0
0 J IO I$ .2 0 2 S' .JO ~.$
"a"
Variation in r e i s ue t C · in
dist ance of l roi side o t e ox.
3
Next he used a box 26 x 26 x 37 inches with the corners
filled in and readings taken as ab ve, but it sades over
the lamps. Shades were as follo~e:- l, Albaj 2, Opalj 3, Dec
orative Shade; 4, green metal painted insi e ith Lithophone;
5, Porcelain lined green outsi -e.
Readings ere as follows:-
'
'
1
'
2
'
3
1
4
'
5
I
Shade No.
I
'
'
I
'
I
I
I
Point by Point
'
90. 3
1
90.0' 82 .2
1
84.8 I 77.5
I
I
Box
'
90.0, 88 .6 , 84. 5, 78.1 I 70.2
'
Next a cube with t e c rners fille • T e results o tain
ed by shade No. 4 were the sam e s before,but ith the green
colored white sho ed an increase of 82. 8 tJ, a o i n -· an error
due to the abeorbin~ reen surf ce. A si ilar tre t nent of
No. 5 showed an increase of 75.3
•
The conclusions drawn ere as follo s:-
"It see s fair to say t t no inte ·r tin hotom er of
this tyue is an instrument of i g recisi on.
For sources of simil r distributi on a rectangular box may
be substituted for a e here.
A cubical box with t he corners el i i nate as de cribed is,
for practical purposes, a satisfactory substitute for a sph re
even for dissi11 ilar and asymetric souro e • "
No matter o accura e t he box photometers ma be t h
globe photo eter nolds its p ce as t e be st.
4
CHAPTER II
THE ULBRICH SPHERE
Professor Ulbrich's spherical photometer, which permits
the measurement of the mean spheric l c n le power of a lamp
by a single settin, consists of a lar es here, with its in
ner · surface painted white. The so )roe of light to be m easur
ed is placed inside of the s here and t ' e illumination at any
openin.__, in the surface o tl e sphere (the 'irect
intercepted by a screen) is proportional to tpe me·
ing
can le power of the lamp. A globe oft ·s K ir integrates
very successful y t .e illumi. tinM ffect of any so re s . It
involves the use of a hotornetric device an a st n r
cadescent lam.
•
The followin n}Q.t em tic 1 tre~t ent sos t t t e in-
tensity of illumin tion at any oi ton t e in erior of a
sphere is proportional tot tot 1 flux from t e so rce con-
tained in it provided t ' t t
screen d off •
irect r from the lamp re
Let the direct illumin t ·on at a oi r. t A be IA. Tent e
intensity of illumin tion at a po i n B due to the li t reflect-
ed from a small area de at A will be
5
KlAd& ~o!2d • KIAdS ~
l 4r
If this is integrated over the hole sphere e get
KF 1
4r2
and if we take into consider tion successive reflections e
have
(
l \
4
+ etc7
4r
2
7 ~
a quantity which is proportional to F, t e total flux of the
source.
K · a a constant reflecti n.
Thie calculation is true onl o t 1e s p osi tion that
there are no absorbin surfaces w'th"n tea here .
it in
t es here t. re are unavo · ably tw s c surfaces, t
scree
and t.e opaque parts oft e unit. T he bot iz reduce errors
which may be made a minimum by pro ,er ch ice an
e of
the ". Throu practice i• as bee fun et t o use op ue
1creen and to place the un·t ab vet ce tre o t .e a r .
The fol owing t ' ill iv
0
so e idea of t ~ ·e f . i e C
of the sphere. Ul rich in one of hi first person this sub-
ject described an ex eri ent it a c rbo fila et la , one
side of which w as overe i th o pa ue 1 1 t p int • egin in
with t~e painted side turned to r t e ow, and t rn·ng it
throu h an an le of 90° at time t 1 e ollo ing result ere
obtained:
0°, 100: 9J
0
, 1 1 3· 1 o
0
8 l· 270° 1 0
1
, - ., ' . , ' .
,.,
An experiment p rfo ed by Block is shovm ir: t he follo -
- ------------------------------
1
· 1 rich, Elect. Zeit. 2, p 5 5, 19
Bloch, Elect. Zeit. 46, p 1074, 19 5.
•
6
ing tables:
A. Effe ct o f Position of Lamp in Sphere.
; Source ' S. C. P.' Re l .
' ' VaJ •
'Carbon ' '
1
filSJ .ent' 21.i ' l
t 6 amp I I
'arc a.c.• 225. t 12.l
'15 amp ' t
' Source at Centre'
' Readj n~• Rel ,Val ,' Rewiin
I I t
I 43 I 1 I 44 . 5
I I I
47a
'
I
t
11 .0
I
I
550
'
' _..Rel . Val ',
I I
l '
'
12 . 3 '
' arc a,c,' 1000 47, 3 !
l 800 41.8 • 2060 46.3 t
------ -----------
B. Compar i son of Point by Point ethod
a nd Int egr tin Shere.
I I
P.
'
Source
b r p .
I
S. C .P. Sphere
t
Error
' ' '
'
I
'
I
•carbon Incandescent
'
21.l
'
21.1
• Sta
,
r
• 2 amp arc
I
81 . 5
I
4.0
t
3.1
1
6 amp arc
'
255 .0
I
260. 0
t
- 2.
' Flaming arc
'
100 .o
I
980.
t
-2.7
t
ig ... t a gle arc
'
750.0
'
730.0
t
2.1
' 2 am arc (Intensi-
1
2350 .0
'
24 0.0
I
'
fied)
I I
'
I t
t
'
I
t
'
'
f
•
•
From Table A it can e see t t t.e ec centric po iti n
is better, and it was found also tat
small chanve s in position w~re inm teri
Values of h/ r from 0.08 to 0.15 g v
rer t _is o si tion,
•
T he error at t he centre is robably ue to abso tion an
i nterf erence .
Usin the eccentr·c position t ~ uthor took a seri s
of readin s usin different sources, t e m.s.c. p . of w ich
w ere obt a i ned b the point by point et
•
The const ant of the s here w s obt i ed by e ne of a
carbo n fil a.rrient lam , t e results of
A highe r degr ee of accur cy
iment er s, butt~ e above 1ill ive a
ex )ected f r om a s ere or lo e oto
ic are in ta le B.
s e ex r-
e of lat ay be
er .
Knowing the accuracy an other advantages o_ a glo e hoto
meter an realizing the need for one, it was deci ed to build
one five feet in diameter. Several lans oft e actual construe-
tion were thou .tout. One oft eee las was to make t
sphere
of concrete, but t.ie was abando
beca se of its makin too
heavy an instrument. Anotl er idea was to ake a tins here an
line it with plaster of
ris, but this also ad its disadva -
tagee. T r e layout finally deci ed upon wr s to construct t' e
sphere of No . 28 galvanized iron an t o coat t e i · si e with
white pai t.
The develop ent oft r
,,: s
0 e o t b t e gor
method. The surface w a s
.
V
.
e int eix~y sectors a an
gore
1/3
size was dra -t o seal
>
ana ro t · s a fu s ze
tern was made. The sections ere cut, all
.
/4"
f rivi win r
1
• 1.,-
•
T e
'
ed in t follo~i
O
manner. Two he ing. spnere waa asse
f t gor ispheres were first co structed b rivit ·n t , irt
togeth~r. T~ ese he is.her a were r er · i by
e use o 1" x 1 '
x 1/4" ano-les., bent to t 1e s ane of circle. One a ~1e ent
around the circumfere ce of t.e o e si e of t.e e i re ith ,
two semi circular pieces crosae at rig ta 1 sat t e .ol of
t.e hemispheres. Thee were ten mount e wit: t e o en s·de ver-
tical and tow r e c other. One s held st t·o ' ry t o a se of
4" x 4
11
by vort · cal a alantin braces of e an le ire.
The other w a ri idly mounted i t' e sa e anner u. o 1 a latfor• u
so arran on rollers t ena le it t o be r a m un to t . a ot h r
•
he ie~here, int is nncr fo ui n co l ete s er . A ole 1"
in iamet r \,as m de t t·1e top o t. t o j ce t is e
8
to allow for the introduction oft e source to be tested. The
edge of this hole was made ri
0
i · by the use of anot vr iece of
angle iron previousl y· bent i to the proper shape. A cover for
the opening was made of s eet iron to preven· he esca e of
light from t e so rce tested.
To calibrate the a here it was f ·rst necessary to find t e
mean spherical candle po.er of a lamp by the point by point meth
od so that it could a!terw r be used as a stan r. This lamp
was compared, at 110 volts, by meas of a Lummer- rod un contrast
photometer to a stan a r lam ose me h rizo ·al c ndle ewer
was known. Te lam to be stan
•
r ze , ile it
stood in a vertical positio an r
of t he photo eter hva fro1 b t sources a t bulate . Te
avera e w st ken as the re n. Si il - r re"din s ~er~ ta~en
of the la.mp
tabulated in table I.
T he r eadings were take with const nt volta
0
e on bot lam.s.
This was n d by resit ne e in e c circuit connected
through a maste r resistance tat ¥OU cot trol bot· • E c· volt-
meter was adjusted to re
sistance w a used.
its correct vale bvfore t e m a i re-
g
. .
(
, I I <>
t
r
r"I
v'
' I
f
..
~
~
i
~
~'
f
l
r>
r-
'
I '
\
r
•
1 .
r
.,
--:::
'
.
A
.,
I
.
:t.
/
4
•
.:J
,,..
\ --
.
'
,'
', .
""- __ ,-
'-',
•
,.
•'' .. . ·
,•' .: < d'. .
_.
• ---- - ·
. \
'
'""
1,. .......
i
'
' - -· 1 ~ _ _ :.
i . ·a• .•• - · •·
. t .. . . •· .
\ . . .
, .. .
·"
~ - :: :-;,: .
---
. ,' \, .•
lo • .;-·"
\ >·
\
\
/ ·
.... ~ ..
-\
,
. . A'
.-
. ;.. .· .
...... ~~. ·~···-~'
. .
Table I.
Angl Di at' . Stand rd Di st' . Te st. C.P.Test C.P.Standard
I
99
'
5.510
'
5.490
I
30 . 20
'
30.4
I
'
85
I
5.50
'
5.500
I
30.40
'
"
'
I
a
I
5.520
'
5 . 480
'
30.00
'
"
'
t
75
I
5.525
I
5.475
'
3 .75
I
,,
t
'
70
'
5.5 0
I
5. 420
•
2 . 60
"
I
•
'
65
'
5.62
I
5. 380
'
27. 90
"
I
'
6
'
5. 750
I
5. 250
'
25.40
f
ff
I
55
'
5.760
f
5. 240 25 . 10
"
'
50
t
5.840
t
5. 160 23 . 71
ti
'
I
45
'
5.910 5.0 0
t
22.50
'
f
'
I I
5.99
r
5.010 21.25
'
"
•
I
35
'
6.16
'
4.840
•
18.70
I tt I
'
30
'
. 32
'
4. 6 0
f
16.62
'
tr
I
'
25
I
6.5~0
'
4.470
t
16.00
I
..
'
'
0
'
6.75
'
4.250
t
12 . 00
"
'
15
I
7.060 3 . 940 .50
'
ti
'
10
I
7.420 3.5 0 7.20
t
"
'
t
5
t
7 .8 0
t
3.12 4. 8
"
'
t
7. 60
I
3. 4 4.45
tt t
t
5.500 5.5 0 3 • 40
.
"
t
45
I
5. 650
'
5. 35 26.25
'
t
60
5 .830 5.170 24.75
"
I
7
'
.820 4.12 11.10
t
t I
e fol l o win volt eters were use :
Te t Lam 116 3, r a 110 .8 = 11 volts.
St Lap · 12494, rea 108.5: ll w volts.
re t ~e e results s plotted o ola r coordin te a~er a
•
curve s. o i t·e t tal fl x e itte byte lam, usin candle
po er plotte or t i e correspo ing a le at :hie. it as taken.
Tle lot mar b~ seen in Curv I .
Fro t l e c ndle po er re
•
l. an t e correspon in~ aneu-
l~r read in s as plo ted t e Rousse u dia r a. from w · ch was
foun· t e mea spheriJal candle poJer. The diaw r am. is fo und by
t ~ e fol o in etho . Te values oft altitu es of zones sub-
e · e u· l 10° an le s r e laid OJ.I to sc e alo
tic is . Ont e ho r ~zo tal 1·nes dr wn from the termi as of
10
the successive altitudes, is la.id off to scale the value of t 1a
candle power in t he direction of t.e correspondin angles., t hen
the area enclosed by t he curve asaed through t ese oints of
candle power at various an~les., represents t he total luminous
value of the source of light. The value of tlis area in tenna
of t~e product of t l e scales tow ich t
0 di-
vided by the sum of t }e or i1ates or altitu es will give tl e
mean spherical can le pow r
will give the flux in lumens.
The m ean spherical candle pow r
following computation 26.
vale multiplie by 4 rr
f oun to e · tl e
250 (area) x 2.5 (absc a scale)= 2 .
24 (or in te)
Flux in Luraens z 327. See Curve I I.
In order to calibrate t: e S arp- : ill r o rtable hoto eter t t
was to e used in connectio~ it t~e sp ere ·t as nece s r
to set it u, any distance from t l e st n r lamp an a e a nm ~ -
ber of readinss and measure t~ e i tance of the lam fro t e
diffusin~ screen of the Porta le hotom er en
with a constant voltaue of 11. on t e stan r an a c eta t
current o! 250 milli-amperes on t l e portable hotome t er lam.
The same volt et r a e use i tn·s as int' e
• •
r~ 1.0 s ex eri-
ment. These readin s are recorde in tabl I . Fr mt e la
that candl po er iv· e y it nee s u~re is e ual to foot
can lee was foun t e nw er o. foot c dl t
1
t 8 0 1 eat
the point w ere tl.e orta le hoto et r scre...,n w s form rly lo-
locate . Tis v l ue divi ed
t.e p oto eter rea n g·ves t e
ll
, ..
. l
·,
I
t
{
I
I
·,
- - -- -· :. _ _:_ . -~ ~-~:-4--: -- }
I
.,
. l ;- .
•
. !
.
i
I
•
I
J
I
f .
!
.. l
I .
l
0
7:i i_
: . . ~ ':- · \
r
I
I
!
f
l
correction !actor.
30,4:
25.2
Portable
1.206; 1,206 = 2.02
.592
Table II
Photo eter Rea
•
ings.
1st Readin Di tanc 2nd Readin Dist. C P.Sta. Am on Portable
. - .
'
• 510
I
5 ft.
I
.580
'
5.03 :ft. 30.4
I
.25
'
I
.560
I
ff
I
.563
I
"
I
"
'
"
t
t
.510
'
"
I
.576
I
u
I
"
'
"
I
I
.555
I
"
I
.585
I
II
'
"
I
"
'
'
.562
I n t
.590
If
I
n
'
"
'
I
.500
I
"
t
.597
l
T
I
"
'
"
I
I
.52
I
"
'
.610
'
"
I
"
t
"
'
I
.555
I
"
I
. 6 0
I
u
t
It t f1
1
I
.56
'
"
t
.613
I It
'
"
t
"
'
t
. 51..,
t
"
I
.610
1
I
"
I
"
.4
t ft
I
•
I
"
t
"
t
• 51
I
"
I I t
"
'
I
. 51
1
"
I
'
"
I
"
I
.517
I
"
t I It t
"
'
'
,490
"
'
I II
t
"
'
I
.53
t ti
' '
1
t
"
t
.53
"
I I
If
I
It
I
t I I I I
'
I
'
"
I
.592
"
I
fl I
"
'
f llo
• •
tru ents r sed • in l.
· Iilli- et r o . 8546 .
V olt , ter o . 11 0
•
T e glo
e P
to et r s set u an the stand rd lamp placed
inside nd a number of re di 8 t z:e ith i ff er nt positio s of
t he screen and lamp to scertain if t1e different l ocation of
t ese t objects ul ea can e in t1e photom ter rea ing .
Th r u t are to e un in tabl III and IV.
Table II
•
Lamp 24 i ches fro top.
1
Di of gcreen from lBJ I? I 8"
'
21"
I
I
I
3.45
'
3 . 50 I
'
I
3.70
'
3 • 50 I
'
I
.50
'
3. 4 I
'
I
3 . 5
'
3 .60 ,
'
J
I
3.5Q_
'
3!
'
'
'
. 55
I
3 . 5 r
12
Table IV.
Lamp 12 inches f r o top .
1
Distance of
1
I
'
I I I I
'
' Screen from '
8"
I
10"
'
12"
'
14"
I
18"
'
20 fl . I
22"
I
'lam~
I I I I
'
I
'
I
I I
3 . 50
1
3 . 80 I 3 . 90 I 3 . 50 I
4. 00
1
3. 30 ' 3 . 50
'
'
t
3 .50 I 3. 70
'
4 . 00 I 3. 70
'
4 .00
1
3. 40 I 3 .60 I
r
'
3 .80
t
3. 70
I
4.10 3 .80 4 .10 I 3 . 60 I 3 . 0
I
r I
3 . 80
'
3. 90
t
3 . ro · 3 . 90 I 3 . 50 I 3 . 70 I 3 . 70 I
r I
3. 0
f
3. 90
I
3.SO' 4.00
'
3.70 I
3.90' 3 • 70 I
I
'
3. 90
t
3. 70
I
3.80' 4.10
I
3 . 60 I 3. 6
'
3 . 90
1
t I
4 .10 l 3. 8
'
3.50 I 4 .00 I
3. 0' 3 .80' 3.90'
t I
4 . 20
1
3 . 90
'
3 .60'
41
'
3!80
1
3160
'
3!70
1
Aver· o-e
'
3. 83
t
3.80
I
3 . 77 3. 7
'
3 .81 ' 3. 61
'
3 . 73
r
I I t
'
'
t
'
Te dif erenve i rea ins is due toe e f tigue and v riable
volta e . T1e result s s! o t t t n · is ractically co st nt
fo r all positions of t.e sc r een. P ~ctice an ex er iments of ot ers
sho t t be t resul~s are the sou rce is .laced fro t he top
about 15 to 20 /J of t e i eter of t · e snhere. In all followin
tests t e 1
~ as be pl· ced 1 i c es f r om t 1e top a 1 t ' e screen
22 ices from t ~ e so rce.
T ' e stand r lamp w s lace i t : e gl e a e er y supplie
at constant volta~e (11 •• 110) and a number of re ·ins taken to
fi d t e rea ·
o t e ortable t _ t ould be the num er of foot
c ndles co r --es on in to t_Le 26 m. s . c . p . or 327 lwnens of the stand-
a r d.
Fr o. t ble V t~is is fou d t be 3.48.
13
I
I
T able V
Readings of Standard La.mp pl aced in t he
Globe Photo et er .
Volt s ap lied • Amps or Port
I
Re
'
I
r
'
to Standar d ab l e 1 p
• 110. 8 : 110
. 250
3 . 50
_ ;..::;..;:;..;:;..z-::.~,.;,....--------~----
I
I
"
I
I
"
I
f
"
I
J
"
'
t
"
'
"
'
"
I
II
'
n
'
tt
I
ti
'
'
I
I
1 I
"
1
ti
'
n
t1
II
1
ff
If
u
It
"
'
If
fl
Avera e
3. 40
3 . 30
3.40
3. 50
3. 40
3 . 50
3. 50
3 . 60
3. 40
. 50
3. 60
3 . 60
3. 50
3i 50
3 . 4
1
I
'
I
I
l
I
I
t
I
I
I
Since t e l umens of t1e stan rd an anot er la.mp are di rect-
ly proportional t o thei r r sne tive
red.
8 0 tined b t he glob
..
photo ete r tne
•
s. herica. candl o ver or tot· 1 e a of a
l uminous sour ce e h ad by acin
·+
•
i e t he lo e a read-
'Y
J. ... l.
ings t aken. Sever 1 sour ce s may e cop re as ell t determine
t heir relat ive luminosity .
The absorption of ev r 1 edia be f n by illumi ting
t her by a revio' sly taste 1, l p an 1 cin - t e .. inside t \ e s! here
.
and r eadi ngs taken of the a ount 0 lig t tted y t e
•
Tl t s.,
t he l Ul e is of the bar lam inus t· e lu. ens
.
by t e b- en cov re
sorbin mediu· ·ves the amo nt of absor· tic of t· e mediu
•
The followin c cmparativ test were on aev n st reet lam
balls wit h a 100 att ~zda "C" 1 pl ced i si e aa t he s rce of
ted by 1, 2, 3, 4, 5, 7, an Ab~ e
14
15
teats were made as befo e
th a constant v ltage an co stant
current. Twe ty readings of 80.C 'Tere t ken
•
order to
•
in ive a
more accurate avera
•
could be use s t
exa"'t
read·nc- . e
'•
l.C
The results of this teat are tabul te
•
t l e J.ll
•
l , VI .
a
o :
r et lls.
'
Bare
'
Kin of Ball
I
lam~
'
I
'
I
. lio . l No.2
1
N o
1
3
'
lo .4
1
Ho.5
1
No.7
I
Alba
I
I
.o 7.2
'
7.4
I
6.3
'
7. 0 I 6 • 6
'
5.0
I
6 .2
'
I
8.4
I
7.4
J
7.3
I
6 .2
'
7.0 I 6. 7
I
5.3
'
6.5
I
'
7.9
I
7.0
I
7. 6
'
6.2
'
7. 2 •6.8
'
5.2
I
6.1
I
'
8.2
I
6.9
J
7.2
I
6.4
I
7.1 •6. 8
'
5.0
I
.l
'
8.4
'
7.2
'
7. 2
'
. 4
I
. 4 •6 . 7
I
5.4
I
6 . 5
'
I
8.4
l
7. 2
J
7.2
'
.2
I
7.1 •6 . 8
I
5.~
'
6 . t
I
,:,
I
7.0
•
7.4
1 I
7 .
t
. 8
t
5 • .
'
t
. '"'
I
•
• •
'
8 .5
I
7. 2
7.r
1
6 .
'
7.
•
I
5.1
I
•
'
8 .6
I
7.2 7.3 . 2
I
7 • I 6 • 5
'
5.2
'
. 5
'
8.6
'
7.4 7.2
,
'
•6.8
I
5. 3
'
. 5
• •
'
8 .
I
7.1 7.3
I
7. 6 '6.
'
5.0
I
6 .5
•
I
8 . 5
'
6.9 7.5 .8
I
7. •6 .8
I
5.2
I
•
I I
6.9
t
7.4
'
t
7. I 6 • 9
I
5. 2
'
.6
• •
I
8
t
7.2
'
7.3
t
6.8
I
7 . 4
t7.
I
5 . ...,
I
.6
I
8 .4
'
7.0
I
7.4 .8
'
7.4 •7.0
I
5.4
'
6.3 I
I
8.2
'
6.8 7.2 6 .
1
. ...,
•
5.1
. t
6 .
I
8 . 6
'
7.
I
. :)
•
t
• 8 5.1
I
•
I
'
8.5
I
6. 8 • C
'
7. •7 .1
'
5.
'
6 . 5
I
8 . 4
I
7.
l
'
7. 3
1
7. 2
'
5 . 2
I
6.5
•
'
8 . 2
'
6. 7 . 2
6 .8
'
7.2
t7 . 0
'
5. 2
t 6.
,
•Av.8 . 35
I
7.08
r
7. 315'
6 .481 7.28 •6.93!
t
5.20 t 5 • '111
From table VI was foun t e tot 1 lumens em i ted by t e bare
la.mp and e ch glo e an r e t t e er cent of baorpti n C 1-
culated. T e r sult ... a r e 0 t i e in t e followin nner.
Lumens of standa r d x re
.
= L
of J. ·· az a.
reading of stan
Lumene of standard X
-
readin of ball I - Lumens e itted
y I .
raadi stand r
Lwr.eno o f Mazda - Lum
I x 1 0 _
'° cif absorpti •
Lumens
Table VII
A bso rpt ion of Jedia .
'
Ob:fec~ : Te:sied
-, :
Lµplen s :•: .. _ ~~i~p:s ~b so r bed 'I of
abgorptio n_'
• Bare M azda C.
'
785
I
0
t
0
'
'
i:ro .1
I
665
'
120
I
15 . 3
'
I
U o. 2
'
688
'
96
t
12 . 25
I
I
M o.I
!
610
'
175
I
13. 7
I
I
lo .4
I
685
'
100 12.75
'
'
N o.5
I
643
'
142
I
18.1
'
'
o.7
'
49
t
295 38 . 2
'
'
lba
'
60
t
180
I
22.9
Fro?Jl t he above calculati n i can be seen t t iffe rent rade
of ba lls and nat rial h~ve greater abso r bin qualities. Te abo ve
te st s al so s bo some of the ractical va e o f t e glo e ho·o· eter.
Even though a box or an ap r oxi. ate spher ma~ be use ~ f r rug re
sult s, i t can be plainly seen tat t e more ne~rly t he p oto eter
is a spher e t e more accur· te are t t e results t t can be h
•
16
-= I ===- - 1-1-1-+--I~
r -, --
-+r~-r
I 7 -.---.-1-i--,--,,--,
---.--
-, I I I
0
•
UNIVERSITY OF SOUTHERN CALIFORNIA
ELECTRICAL ENGINEERING DEPARTMENT
ELECTRICAL MEASUREMENT 0 MB R , 1919
CALIBRATI N OF mJ\IBT R--A voltmetsr may be
arranged in aeries with re iatan e n a ba tery ao
that any desired deflection my be o tained. hen s o
arranged its calibrat · on 1 a ·fecte or ~ a ecif
number of orking points, by usin the potentiom ter to
measure the potential dro across the eter for each
desire point .
Th po entio et r o er ith three istinct
sources of voltage. A tandard ce 1 is first bal~nced
against battery sot at a current of just one-fiftiett
OI an ampere nows thr oug th circuit of the otentiomet r.
hen hie is done, t e voltage t o be easured is b 1 n e
ag inst a portion o e ro in 1 ircuit, the ortion
r q~ired being arrange so s t o in ic ~te the unkn o n
voltage irectly. Pree tions must be take o aee t
n change of current takes l ~ce d r n t e o erutio
of balancing, and the potentiome er circuit must b
thro~n b ck and fort bteween t e stan r ce 1 n
th unknown voltageuntil the galv nometer re aina t
zero on both cir uita. Arrangement is m~de on the
inatru ent for doin t1ia.
The d t resultin fr o thi libr tion
r ,ay b lotted a or in corr cti n curve for
that p rticular voltmeter.
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Asset Metadata
Creator
Brown, Earl F.
(author)
Core Title
Construction and tests of a globe photometer
School
College of Liberal Arts
Degree
Bachelor of Science
Degree Program
Electrical Engineering
Degree Conferral Date
1916-06
Publication Date
06/05/1916
Defense Date
06/05/1916
Publisher
Los Angeles, California
(original),
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
OAI-PMH Harvest
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theses
(aat)
Language
English
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Digitized from microfilm by the USC Digital Library in 2023
(provenance)
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Sc '16-2 (call number),etd-BrownEarl-1916.pdf (filename)
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Document Type
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Rights
Brown, Earl F.
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texts
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(batch),
Undergraduate Papers
(subcollection),
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(contributing entity),
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(collection)
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