This item is only available as the following downloads:
UNITED STATES ATOMIC ENERGY COMMISSION
VICTOREEN INSTRUCTION MANUAL
Audeton, Model 376
December 8, 1950
[TID Issuance Date]
Victoreen Instrument Company
IL Technical Information Division, ORE, Oak Ridge, Tennessee
Styled, retyped, and reproduced from copy
as submitted to this office.
PRINTED IN U.S.A.
PRICE 15 CENTS
AEC, Oak Ridge, Tenn., 12-8-50-675-A24346
VICTOREEN INSTRUCTION MANUAL
Audeton, Model 376
The demand for a dependable radiation detector of the "personal variety" has long been axiomatic
in nuclear physics circles. This urgent and obvious need has been responsible for the development of
the pocket audio detector depicted in this report, which is a comprehensive summary of experimental
results obtained during the development of this project. Included in the body of the report are photo-
graphs, charts, schematic diagrams, and service notes of the salient features produced in the finished
detector. The terminal section contains an analysis of the conclusions and recommendations pertaining
to future refinements of the various design factors.
In formulating the original design, an attempt was made to provide a light weight, compact, and
reliable instrument possessing sufficient flexibility to be applicable to the multitude of monitoring
details which do not warrant a complete quantitative measurement or for those surveys which are
beyond the scope of the cumbersome and expensive laboratory meters. In its final form the detector
consists of a gamma-sensitive subminiature Geiger tube together with all associated circuit components
housed in a pocket-size case of such design that in appearance and operation the unit closely simulates
the familiar hearing-aid receiver. The conventional ear-mold-insert transducer is employed to pro-
vide oral indication of the signal magnitude.
The inherent simplicity of the requirements of an audio detector presented an opportunity for a
radical departure from conventional designs in a manner which adds appreciably to the intrinsic value
of the instrument.
Results obtained from the experimental model have been entirely satisfactory and completely
substantiate the feasibility of the basic principles involved. Proper pursual and exploitation of these
principles should produce an instrument worthy of filling the heretofore unpervaded gap in the
Height, 6 in.
Width, 3 in.
Depth, 1% in.
Weight, 1 lb, 10 oz.
Case material, cast aluminum
Finish, chromic anodizing, flat-gray paint
Accessories, individual ear molds (right or left), carrying strap (optional)
Operating voltage, adjustable 0 to 450
Nominal generator frequency, 150 cycles
Output impedance, 30 ohms
Earphone impedance, 30 ohms (magnetic type)
Generator coil, 700 turns No. 30 enameled wire
Coil resistance, 10 ohms
Transformer. Turns ratio, 150/1
Resistance (primary), 10 ohms
Resistance (secondary), 9000 ohms
Inductance (primary), 130 mh
Inductance (secondary), 290 h
Rectifier. Forward resistance, 1.5 meg ohms at 15 volts
Back resistance, 500 meg ohms at 15 volts
Characteristics of Geiger Tube
Length, 31/2 in.
Filling, methylene, bromide, and argon
Plateau length, approximately 30 volts
Plateau slope, approximately 10 per cent
Background, approximately 25 cts/min
Temperature range, +135 to -30F
Life, approximately 5 x 107 counts
Operating time, approximately 2 hr per charge at background counting rate
Indicator, magnetic earphone
Sensitivity, gamma. Any intensity greater than average background rate is detectable.
Calibration. Accuracy of calibration is contingent upon an estimate of the counting rate and will
vary with aptitude and experience of the individual operator.
The pocket audio detector is a gamma-sensitive instrument consisting of a special subminiature
Geiger tube, power unit, matching network, and miniature insert-type earphone. All components, with
the exception of the earphone, are housed in a pocket-size aluminum case simulating the appearance
of the familiar vest-pocket hearing-aid receiver. This construction lends itself admirably to a
variety of applications, and the extreme compactness allows the unit to be worn for long periods of
time without undue fatigue to the operator.
Energy to operate the detector is stored in a special tank condenser which is periodically re-
charged by a self-contained spring-actuated generator. The storage capacity of this condenser is
sufficient to operate the circuit for a period of time far in excess of that necessary to complete the
average survey. For extended periods of operation the generator may be recycled as often as
Normal operation of the detector is indicated by an audible signal (approximately 25 cts/min)
produced at a comfortable level in the earphone. As the counter is exposed to radiation, with a
consequent increase in counting rate, the effective acoustical level produced by the earphone like-
wise increases, thereby producing maximum signal volume at a time when it is most needed. An
approximation of the radiation intensity can be gained by estimating the frequency (average counting
rate) of the audio signal as heard in the earphone.
The circuit arrangement chosen as most suitable for the final model of the detector is a composite
of several designs tested during the development stages and is shown in complete schematic form in
Successful operation of the counter depends upon the storage capacity of its tank condenser (101).
Assuming infinite leakage resistance in the condenser itself, the discharge rate would be entirely a
function of the energy expended in the Geiger tube which for the type VG-7 is approximately 6 x 10-10
coulomb per pulse (expressed as a mean value since the individual pulse charge is a function of the
overvoltage of the tubes).
Under these theoretical conditions the operating time for a single charge of the condenser would
be determined by the useful plateau length of the Geiger tube and its average counting rate during the
operating period. Thus a charge of 5 microcoulombs, a plateau length of 50 volts, and an average
counting rate of 25 cts/min would give a total operating time per charge of 5 hr and 30 min. Obviously,
this theoretical value cannot be achieved in actual practice since a practical tank condenser must
necessarily be a compromise of size, capacity, voltage rating, and internal leakage resistance.
Commercially available condensers were found to be unsuitable with an approximate leakage
resistance of only 1 x 1012 ohms. Extensive research with various dielectrics resulted in a sizable
improvement in this value. The final selection was a styrene dielectric condenser of 0.1-Af capacity
and a 450-volt operating test, housed in a hermetically sealed container with connections terminated
through Kovar-glass seals. Total leakage of the finished unit was found to be approximately 2 x 1013
ohms. Additional protection to the surface resistivity of the glass seals and the press of the Geiger
tube was provided by processing their surfaces with silicone varnish dry film.
A leakage resistance of this order of magnitude provides an average operating time of nearly 2 hr,
which can be considered satisfactory for all normal demands likely to be made of the instrument.
The type VG-7 Geiger tube illustrated in Fig. 8 has been developed specifically for use in the
pocket audio detector and is a methylene-bromide-argon self-quenched filling. A typical plateau curve
is shown in Fig. 9. The operating region of 300 volts was selected to be consistent with the available
circuit parameters. Operation in this region somewhat limits the available pulse amplitude; however,
the average height, Fig. 10, over the usable portion of the plateau was found to be more than adequate.
The use of a seemingly desirable plug-in base instead of the flat lead press has been purposely
avoided in order to maintain an extremely high leakage pass across the lead press, since a low
resistivity (either volume or surface) at this point means a serious loss of condenser charge which
would result in an appreciable decrease of unit operation time.
It will be noticed that a considerable increase in tube efficiency will be experienced over the life
span, see Fig. 13. This effect can be ignored for all practical purposes, since measurements made
with the instrument are of a qualitative nature only.
A special coupling transformer (102) is utilized to provide the necessary impedance matching
between Geiger tube and earphone. At the same time, a frequency-conversion effect is obtained by
proper coil construction and choice of lamination material. This conversion is necessary since the
energy distribution of the extremely narrow tube pulse is confined to a portion of the spectrum beyond
the response limit of the earphone, indicated in Fig. 14.
After conversion the pulse as measured at the receiver input appears as illustrated in Fig. 16 and
contains adequate power to drive the earphone at normal loudness (approximately four bars into a 2-cc
cavity) for the average listener.
Virtually automatic control of the volume is accomplished by the relative increase in effective
acoustical power with increase in counting rate as shown in Fig. 17.
High Impedance Output
An alternative output circuit arrangement applicable to surveys involving unusually high counting
rates is diagrammed in Fig. 18 and operates in the following manner.
Supply voltage EB is made equal to the Geiger-tube operating voltage V0 plus the striking potential
of neon tube N.
Conduction of the Geiger tube allows the series capacity combination of condenser C and earphone
R (crystal type) to accumulate a voltage charge at a rate determined by the average counting rate of the
Geiger tube until voltage e reaches the ignition potential of neon tube N. Conduction N discharges net-
work RC until voltage e is again reduced to the extinction potential of tube N. During the conduction
period the current decay through network RC produces an audible pulse of saw-tooth shape and
considerable amplitude in receiver R.
This output pulse varies with the counting rate of the Geiger tube at a dividing ratio of approxi-
mately 80/1, see Fig. 19, thereby enabling the operator to estimate small percentage changes at the
higher counting rates.
In addition to the extremely large output signal provided, this arrangement has the additional
advantage of requiring no output transformer, which would mean a considerable saving in weight as
well as component cost.
Figure 20 shows an assembled view of the completed generator. For clarity of assembly plus a
thorough understanding of its operation, an exploded view of the same generator is given in Fig. 21.
Energy to actuate the mechanism is derived from the preloaded mainspring (114). Several preloading
turns are given the spring barrel in order to place the operating point at the upper, or maximum,
portion of the curve for the spring power output, Fig. 22, thereby obtaining maximum operating torque.
Withdrawal of the pull string (115) gives the spring barrel a differential operating torque of two
additional revolutions, at the same time disengaging the brake arm (210).
Upon release of the pull string the spring's operating torque is transmitted to the magnetic rotor
(105) which is coupled to the spring barrel through ratchet and pawl (224) and a step-up gear train
(ratchet slips in the winding direction), thus accelerating the rotor until it has reached maximum speed.
Unwinding of the spring barrel allows the brake arm (210), which is controlled by a spiral cam (225),
to again engage the brake drum (229) attached to the rotor shaft (218) thereby retarding further
rotation of the rotor. (Braking is applied at this low torque point in order to relieve the cam, which
operates at high torque, of any undue stress.) The generator is then ready to be recycled.
After the spring barrel has come to rest, the string mandrel continues to rotate part of a
revolution due to the action of its own driving spring (217). This action tends to keep a constant tension
on the pull string, thereby holding the plastic ball tightly against the O-ring seal.
The extra excursion of the string mandrel at the start of the unwinding cycle provides a slight
impact to the spring barrel and assists the main spring in overcoming the "dead center drag" imposed
by the magnetic rotor.
In addition to the prime function of braking, the brake arm (210) also actuates the switch (108)
through an actuating arm (207). The sequence of this operation is adjusted to operate the switch just
previous to the application of the brake shoe, thus isolating the tank condenser from its voltage source
and preventing partial discharge, which would otherwise occur through the supply impedance. It should
be noted that the stationary switch contact (241) is supported entirely by the condenser terminal, an
added precaution in maintaining a high circuit impedance at this point.
Signal output may be turned off at any time by withdrawing the generator pull string only halfway.
This completely discharges the tank condenser thereby stopping counteraction.
Output from the generator, Fig. 24, is fed directly to the primary winding of a step-up transformer
(102), the secondary of which supplies a voltage multiplying circuit consisting of rectifiers (106) and
condensers (113). Output from the multiplier provides high-voltage direct current to charge the tank
condenser and in turn to operate the Geiger tube.
In order to accommodate a wide range of Geiger-tube operating voltages, a semiadjustment of
generator voltage is accomplished by the addition of a rotor shorting ring (230), the relative effects
of which are given far different ring sizes in Fig. 26. Final and precise voltage adjustment is obtained
by proper selection of a load resistor (111). (See Calibration Instructions.)
Of particular interest is the manner in which voltage regulation is accomplished. The secondary
winding of the transformer (102) in conjunction with the condenser (112) comprises a parallel resonant
circuit tuned to the nominal generator frequency of approximately 150 cycles, as shown in Fig. 27.
As a result of this resonance, automatic voltage limiting is obtained. Since maximum voltage is
reached at the peak of resonance, further acceleration or deacceleration of the generator's rotor
(change in output frequency) only results in decreased output voltage. Circuit loading, with its asso-
ciated lowering of circuit Q, produces a broadening of the response curve, Fig. 27, and results in an
output regulation curve as shown in Fig. 28.
MAINTENANCE AND REPAIR
Replacement of Geiger Tube
Replacement of a tube having a different operating voltage from that of a tube previously contained
in the detector requires a complete recalibration of the voltage supply. The necessary instruments are
(1) precision decade resistance box or 10-megohm variable resistance and (2) electrostatic voltmeter,
0 to 500 volts. These are connected at test points indicated on the wiring diagram, Fig. 29. Adjust the
decade box to correspond with the approximate calibration-resistor value selected from Fig. 30; cycle
generator and note voltmeter reading; readjust decade box, recycle generator, and observe new volt-
meter reading. This procedure is repeated until proper operating voltage (previously ascertained
from the tube plateau curve, Fig. 9) for the new tube is obtained.
Cycling of the generator without a calibration resistor in the circuit may cause serious damage to
transformer or rectifiers.
A calibration resistor equivalent to the value indicated by the decade box is then soldered in place
on the terminal strip. If a variable resistor is used instead of the decade box, this should be measured
with an accurate bridge or ohmmeter.
Geiger tubes with an operating voltage equivalent to that of the tube being replaced may be used
without repeating the calibration procedure as outlined above.
Handling of the Geiger-tube lead press or condenser seals should be avoided since contamination
at these points may seriously impair their operation.
Substitution of a standard vacuum-tube voltmeter in lieu of the electrostatic type stipulated under
Calibration Instructions will produce equally satisfactory results by the installation of a few simple
voltmeter circuit changes as shown in Fig. 31. After revision, the meter (with standard input probe)
was found to have an input impedance of approximately 1 x 1011 ohms, which is at least an order of
magnitude greater than necessary for this application.
Scale calibration curves for the converted meter are given in Fig. 32. The apparently serious
departure from linearity is, in this case, relatively unimportant since only a single check point is
needed for any particular Geiger tube. Meter calibration may be rechecked at any time against any
Circuit values indicated in Fig. 31 are for the type 615-A RCA voltohmyst; however, comparable
values will be found suitable for similar meters of other manufacture.
Absence of assembly mounting screws makes removal of the major components an extremely
simple operation. As shown in Figs. 20 and 21, all component assemblies are mounted in the bottom of
the case and held in position by the top cover which is fastened with four flathead case bolts.
If for any reason either generator or tank condenser are removed from the case, a calibration
check of the supply voltage will be necessary before again placing the unit in operation.
Two O-rings (107 and 119) are permanently cemented to the case to provide splashproof con-
A strap fixture (239) is provided at the top of the case for attachment of a neck or wrist strap in
the event it should be desirable to use the instrument for probe work.
The phone jack may be removed for repair by withdrawing its retaining yoke (237) and pressing
the plug insert (236) toward the inside of the case.
The detector described in this report is a composite of special custom-built components repre-
senting the most promising features of the many experimental types tested. This particular version
should be evaluated merely as a prototype for an almost infinite variety of instruments which could
advantageously utilize the basic principles established by this experimental work.
Particular attention is called to the case construction, since considerable saving of size and
weight was sacrificed in order to preserve the similarity between this instrument and its counterpart,
the hearing aid, and at the same time retain the features of reproducibility offered by the use of cast-
aluminum cases and fabricated construction. These are not, however, serious objections, only experi-
mental necessities, which are readily overcome by the adoption of molded plastic parts in the pro-
duction design. Inclusion of a voltage supply capable of accommodating a high-voltage Geiger tube
added further unnecessary bulk. With the advent of the type G-7 low-voltage tube, this reserve supply
voltage had to be dissipated as wasted energy. Calculation of a condensed unit based upon these facts
indicates a possible reduction of at least one-half in weight and one-third in size, with operating
characteristics remaining unchanged.
It is recommended that hermetically sealed case construction be incorporated in any final design.
This has been purposely avoided in the original as being a complexity unwarranted until the design
parameters are more firmly established.
It should be fully appreciated by all who may examine this instrument that the various components
contained therein have been subjected to rather strenuous laboratory treatment with a consequent
suffering of individual characteristics. The results exhibited by these same components therefore
do not necessarily constitute the ultimate which would otherwise be obtained.-
Condenser 0.1 pf
Strap fixture bolts
John E. Fast & Co.
M. L. Muir
Plastic & Rubber
I D 5D5
No. 4-40 x 3/8
No. 4-40 x 1/8
Item Description Dwg. No. Quantity
201 Bottom cover M114-7 1
202 Top cover M114-8 1
203 Coil form M114-47 1
204 Calibration-resistor mount M114-46 1
205 Stator laminations Ml14-45 50
206 Switch mount Ml14-42 1
207 Switch actuating arm M114-41 1
208 Switch-actuating-arm insulator M114-40 1
209 Switch alterations M114-43 1
210 Brake arm M114-39 1
211 Spacer M114-38 1
212 Plate spacer M114-37 1
213 Plate spacer M114-36 1
214 Stator mounting stud M114-35 1
215 Spacer M114-34 2
216 Winding-drum stops M114-33 4
217 Spring-barrel preload spring M114-32 1
218 Rotor shaft M114-17 1
219 Idler-shaft pinion M114-22 1
220 Idler-shaft gear M114-21 1
221 Spring-barrel gear M114-31 1
222 Winding drum M114-28 1
223 Spring-barrel cover M114-29 1
224 Spring drive ratchet and pawl Ml14-30 1 each
225 Spring barrel M114-26 1
226 Spring-barrel shaft M114-25 1
227 Spring-barrel shaft lock M114-24 1
228 Idler-shaft screw M114-23 1
229 Brake drum M114-20 1
230 Rotor shorting ring M114-19 1
231 Rotor alterations M114-18 1
23? Top plate M114-16 1
233 Bottom plate M114-15 1
234 Terminal board M114-14 1
235 Phone plug M114-13 1
236 Phone-plug parts M114-12 2
237 Phone-plug parts M114-11 1
238 Ball M114-18 1
239 Strap fixture M114-9 1
240 Switch arm M114-44 1
241 Condenser contact arm M114-48 1
Fig. 1-Complete instrument.
Fig. 2-Complete instrument with cover removed.
1m T-w' 102
Io? 102 120
Fig. 3-Exploded view of instrument.
350* 3400 3300
10 20* 30.
1400 150. 160 470. 180 190 200 2100
2200 210 2000 1900 180 170- 160 1500
Fig. 4-Sensitivity field pattern, horizontal.
400 300 20 100 3500 3400 330
3200 3300 3400 350 0 100 200 300
/ / "
// / -, \,
140 1500" 160o 170' 180 190 2000 210' 220
220 240 200 190 160 170o 160o 1500 140'
Fig. 6-Sensitivity field pattern, vertical broadside.
1500 160o 1700 180 190 2000 2100
210 200 190 180 1700 160 1500
Fig. 5-Sensitivity field pattern, vertical edgewise.
30- 20, 10. 3500 340 3300
330 3400 3500 0 10 20 30
U. NTS PER MINUTE
\ 2, 00 /
106 106 106
1C2 71+ f l 1 + I
Fig. 7-Schematic diagram of audio detector.
Fig. 8-Geiger tube.
285 340 335
Fig. 9-Geiger-tube plateau.
265 290 345
Fig. 10-Geiger-tube pulse amplitude.
Fig. 11-Geiger-tube pulse shape.
Fig. 12-Geiger-tube temperature coefficient.
Fig. 13-Test of Geiger-tube life.
FREQUENCY, CYCLES PER SECOND
Fig. 14-Curve for earphone response.
INPUT FREQUENCY, CYCLES PER SECOND
Fig. 15-Curve for transformer response.
00 I I I
O 200 400 600
Fig. 16-Output-pulse shape.
0 5000 10,000 15,000 20,000
COUNTS PER MINUTE
Fig. 17-Acoustical output.
Fig. 18-Schematic diagram of output circuit.
10,000 20,000 30,000
GEIGER TUBE, CTS/MIN
Fig. 19-Output dividing ratio.
220 22 213 209 240 207 210 105 230 214
j I i
,005 AWL abl&.0
233 221 224 223 14 222
225 227 203 205 232
Fig. 21-Exploded view of generator.
NUMBER OF TURNS
Fig. 22-Power-output curve for spring.
Fig. 23-Data for gear and coil. Ratio: 50.4/1.
A 72 48 Standard tooth, 20-deg pressure angle. Cen-
ter distance, 0.860.
B 10 48 Long addendum, 20-deg pressure angle. Cen-
ter distance, 0.860.
C 56 64 Standard tooth, 20-deg pressure angle. Cen-
ter distance, 0.570.
D 8 64 Long addendum, 20-deg pressure angle. Cen-
ter distance, 0.570.
OUTPUT FREQUENCY, CYCLES PER SECOND
Fig. 24-Generator output voltage.
REVERSE VOLTS 200 -
200 150 100 50
0I I 20 30
2 FORWARD VOLTS
40- 30. 201 10 3500 3400 3w0. 320*
320o 330, 3401 3501 0 i00 201 30, 40-
400 150 260 10 8 350 3490 20 200 2200
2200 21330 200 9350 80 170 4600 3500 40
Fig. 26-Rotor-flux field pattern.60
260Fig. JRof fiel pattern.
Fig. 26-Rotor-flux field pattern.
800I I I I
o I I II
50 o100 450 200 250
OUTPUT FREQUENCY, CYCLES PER SECOND
Fig. 27-Limiter resonance curve.
400 [ I I l 1 I I I I I I I I I I I
10 0oo 10o0
INPUT FREQUENCY, CYCLES PER SECOND
Fig. 28--Output-regulation curve.
Fig. 28-Output-regulation curve.
Fig. 29-Pictorial diagram of wiring. Note: Terminals A and B are check
points for voltmeter and decade box, respectively. Chassis ground is common
2 4 6 1
LOAD RESISTOR, MEGOHMS
Fig. 30-Calibration-resistor chart.
Fig. 31 -Schematic diagram of changes in voltmeter circuit. RCA junior voltohmyst, type 165-A.
200 400 600 800
Fig. 32-Voltmeter calibration.
END OF DOCUMENT
r'^ A i >
UNIVERSITY OF FLORIDA
3 1262 08917 1101
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID EQDMS38WQ_2Y48DN INGEST_TIME 2012-12-07T22:22:55Z PACKAGE AA00012255_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC