1551-C Sound Lever Mtr., Manual

GR 1551-C Sound Level Meter_0001.djvu

INSTRUCTION MANUAL

Type 1551-C

Sound-Level

Meter

a

GENERAL RADIO

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CONTENTS

Specifications

Section 1 Introduction.

Section 2 Operating Procedure ,

Section 3 Calibration . • .

Section 4 Service and Maintenance .

Section 5 Type 1262-B Power Supply .

Handbook of Noise Measurement

This 282-page book, by Dr. A . P. G. Peterson and Ervin E. Gross. Jr •• of the Gener a l Radio Engineering Staff, covers thoroughly the subject of noise and vibration measurement. Copies are available from Ge neral Radio at $1.00 each. postpaid in the United States and Canada.

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Type 1551-C

Sound- Leve I

Meter

Q

Copyright 1968 by

GEN_~~~h ~~.91~J~NY

West M assach u setts USA 01781

Form 1551.0110.0

10 1276

December, 1968


SPECIFICATIONS

Sound-Level Range: From 24 to 150 dB (re 20 ;.tN/m2).

Frequency Characteristics: Four response characteristics, A, B,

C, or 20 kHz, as selected by panel switch. The A-, B-, and Cweighting positions are in accordance with USA Standard S1.4·

1961 and IEC Publication 123, 1961. Frequency response for the

20-kHz position is flat from 20 Hz to 20 kHz, so that complete use can be made of very wide-band microphones such as the

1551-P1 Condenser Microphone Systems.

Microphone: GR Type 1560-P5. Accessory condenser microphone is available.

Sound·Level Indication: Sound level is indicated by the sum of the meter and attenuator readings. The clearly marked, open-scale meter covers a span of 16 dB with calibration from -6 to +10 dB.

The attenuator is calibrated in 10-dB steps from 30 to 140 dB above 20 ~tNfm2.

Calibration Accuracy: When amplifier sensitivity has been standardized, the absolute accuracy of sound-level measurements at

500 Hz is within ± 1 dB and at all frequencies is in accordance with the USA Standard.

Panel adjustment is provided for standardizing amplifier gain with internal calibration circuit.

Absolute acoustic sensitivity is factory calibrated at 500 Hz.

Microphone response and sensitivity are measured in a free field from 20 Hz to 15 kHz by comparison with a WE 640AA laboratorystandard microphone with calibration traceable to the National

Bureau of Standards. Complete electrical frequency-response measurements are made on each instrument.

The 1562-A Sound-Level Calibrator or the 1559-B Microphone

Reciprocity Calibrator can be used for making periodic over-all acoustic checks.

Output: 1.4 V behind 7000 0 (panel meter at full scale). The output can be used to drive analyzers, recorders, oscilloscopes, and headphones. Harmonic distortion (panel meter at full scale) <1 %.

Input Impedance: 25 MO in parailel with 50 pF.

Meter: Rms response, and fast and slow meter speeds in accordance with USA Sl.4-1961 and IEC 123, 1961.

Environmental Effects

Temperature and Humidity: Microphone is not damaged at temperatures from -30 to +95°C and relative humidities from 0 to

100%. When standardized by its interna I calibration system or a

1562 Sound-Level Calibrator, the instrument will operate within catalog specifications (for panel-meter indications above 0 dB) over the temperature range of 0 to 60°C and the relative humidity range of 0 to 90%.

Magnetic Fields: When exposed to a 60-Hz, 1-oersted (80 A/m) field, the sound-level meter will indicate 60 dB (C weighting) when oriented for maximum sensitivity to the magnetic field.

Electrostatic Fields: Aluminum case provides sufficient shielding, so that normally encountered electrostatic fields have no effect.

Vibration: Case is fitted with soft rubber teet and amplifier is resiliently mounted for vibration isolation. When the instrument is set on its feet on a shake table and vibrated at 10 mils pk-pk displacement over the frequency range of 10 to 55 Hz, the unwanted signals generated do not exceed an equivalent C-weighted sound-pressure level of 45 dB when motion is vertical, 60 dB when motion· is lengthwise, or 40 dB when motion is sidewise.


SPECIFICATIONS (Con't)

GENERAL

Power Supply: Two 1'12 V size D flashlight cells and one 671h-V battery (Burg ess XX45 or equiva l en t) are supplied. An ac power supply, the Type 1262-B, is available.

Accessories Supplied: TelephOne plug.

Acces s ories Available : 1551 -P2 Leathe r Case (pe rm its operation of instrument without removal from case), 1562 Sound-Level Calibrator, 1560 ·P95 Adaptor Cable for connecting output to 1521-B

Graphic Level Recorder .

Mounting: Aluminum cabinet.

Dimensions (width x height x depth): 71/4 x 9114 x 6'.1* ln. (185 x

235 x 160 mm).

Weight, Net, 7¥4 lb (3.6 kg); shipping, 16 lb (7.5 kg), batte ries incl. Ad d 2 lb for leather case.

For a mo r e detailed description, r efe r to Gene ral Radio Experimenter , Au gus t 1 96 1 .

U.S. Patent No. 3,012,197

Figure 1 .

Ty pe 1551-C Sound-Level Meter.

I nse t s how s Type 1262-B P ower

Supply attoched.


TABLE OF CONTENTS

Section 1. INTRODUCTION

1.1 Purpose . . .

1.2 Description .

1.3 Power Supply.

1.4 Carrying Case

Section 2. OPERATING PROCEDURE

2.1 Preliminary Checks . . . . . .

2.2 Operating Procedure. . . . . .

2.3 Selection of Weighting Network .

2.4 Sound Analysis and Recording

2.5 Extension Cable . . . .

2.6 Wide-Range Microphones ·

2.7 Use of Headphones . .

2.8 Background Noise . .

2.9 Microphonics . . . . .

2ol0 Environmental Effects.

2o11 Vibration Pickup . .

Section 3. CALIBRATION

3.1 General . . . . . .

3.2 Observer Influence .

3.3 Preferred Angle of Incidence .

3.4 Auxiliary Calibration . . . .

3.5 Meter Circuit. . . . . . . .

Section 4. SERVICE AND MAINTENANCE

4. 1 Genera I . . . . . . . . o . . . .

4.2 Removal of Instrument from Cabinet .

4.3 Tube Failure. . . o

4.4 Tube Replacement . . .

4.5 Battery Replacement . .

4.6 Replacement of Bias Cell

4.7 Soldering of Connections to Cable Wires.

4.8 Microphone Sensitivity Adjustment

4.9 Internal Noise . . . . . . . .

4.10 Amplifier Gain . . . . . . . o .

4.11 Test Voltages and Resistances .

Section 5. TYPE 1262-B POWER SUPPLY

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Section 1

INTRODUCTION

1.1 PURPOSE. The Type 1551-C Sound-Level Meter (Figure 1) is the basic instrument of the General Radio sound-measuring system. This instrument conforms to all requirements of the ASA American Standard

Specification for General Purpose Sound- Level Meters. An accurate, portable, low-priced meter, it indicates the sound-pressure level at its microphone in terms of a standard reference level (0.0002

~ar).

In addition to its primary use as a Sound- Level Meter, the Type

1551-C can be used as a highly sensitive ac voltmeter. With the microphone sensitiv·ity adjustment (paragraph 4.8) set at -55.5 and the attenuator switch set at 30, the meter has a full-scale sensitivity of 30 microvolts. Voltages to be measuredcan be applied to the microphone connector through a Cannon three-terminal plug.

1.2 DESCRIPTION.

1.2.1 GENERAL. The major components of the Sound-Level Meter are a nondirectional microphone, a calibrated attenuator, an amplifier, an indicating meter, and weighting networks to modify the amplifier frequency response.

1.2.2 MICROPHONE. The Type 1560-P5 Microphone supplied with the

Type 1551 Sound-Level Meter is a new piezoelectric ceramic microphone developed expressly for sound-level meter use. Several features of the Type 1560-P5 make it an excellent microphone for sound-level measurements:

10.0002 f.Lbor "' 20f.LN/m2; cps = Hz.


-2

-

+4

+2

~ft

T

I

50

(CORRESPONDING ANGLE OF INCIDENCE

FOR PLANE WAVES; 70°)

4

20c1s I 00 200 500 lk<;!S

FREQUENCY

2

/

-

~I\

\

10 20

~

Figure 2.

Frequency response of Type 1560-

PS Microphone to sounds of random incidence.

1. a frequency characteristic (see Figure 2) carefully controlled in manufacture to give flat response to sounds of random incidence from

20 cps to 12 kc,

2. rugged, dependable design, capable of withstanding wide elimatic changes (from -30° to 200° F in temperature, from 0 to 100% relative humidity),

3. low temperature coefficient of sensitivity, with minimal change in output voltage from 0°to 200° F,

4. low temperature coefficient of internal impedance; the cable correction is not affected by temperature at the microphone.

The nominal internal impedance of the microphone is 380 pf.

1.2.3 CONTROLS AND CONNECTORS. The controls and connectors on the panel of the Sound-Level Meter are listed below.

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TABLE 1. CONTROLS AND CONNECTORS

Name Type Function

Attenuator 12 -position selector switch Selects meter range.

CAL Thumb- set adjustment Electrical internal calibration or gain adjustment.

METER-

BATTERIES

5-position selector switch Selects fast or slow meter response; provides battery checks.

WEIGHTING 5-position selector switch Selects weighting.

OUTPUT

On-Off

None

Phone jack

Switch built into microphone arm

6-terminal Jones receptacle

Output connection.

Turns instrument on and off (with battery power only).

Connection to Type

1262-B Power Supply.


1.3 POWER SUPPLY.

1.3.1 BATTERIES. Two TypeD flashlight batteries supply the filament

(A) power, and one 67-1/2 -volt portable-radio-type B battery supplies the plate (B) power for the instrument. Contact is made to each battery by spring terminals, and all batteries are secured by a screw -down bracket.

1.3.2 AC POWER SUPPLY: The Type 1262-B Power Supply(refer to section 5) can be used to operate the Sound- Level Meter from a 115-volt ac line. When the Typel262-B is used, its own power switch, ratherthan the microphone switch on the Type 1551-C, controls application of power to the Sound- Level Meter.

1.4 CARRYING CASE. Available for use with the Sound-Level Meter is a leather carrying case with shoulder straps. A hole in the back of this case matches the tapped hole in the back of the Sound-Level Meter so that the instrument can be secured in the case for field use. The cover flaps of the case are equipped with a luggage-type fastener to keep them closed over the panel and with snap buttons to hold them open when the· instrument is in use.

Section

OPERATING PROCEDURE

2.1 PRELIMINARY CHECKS.

2.1.1 BATTERY CHECK. To check batteries, set the METER-BATTER-

IES switch to FIL-l, turn the instrument on by raising the microphone, and check that the meter pointer is within the area marked BAT on the meter face. Turn the METER-BATTERIES switch to FIL-2 and then to

PL, similarly checking that the meter pointer falls in the white BAT area for each position.

Filament batteries should last 6 to 7 days at 8 hours a day, or 30 to 35 days at 2 hours a day. Plate batteries should last 12 to 14 days at

8 hours a day, or 60 to 70 days at 2 hours a day.

2.1. 2 CALIBRATION CHECK. Before using the Sound- Level Meter, make the following simple calibration check. (This check calibrates the amplifier of the Sound-Level Meter, but does not include a check on the microphone.) a. Turn the instrument on. b. Set the attenuator switch to 130 CAL (i.e., with the pointer on the knob toward the window).

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c. Set the WEIGHTING switch to CAL, and check that t e meter pointer falls within the white area marked CAL on the meter face. If not, set it there by adjusting the CAL thumbset control.

2 .1.3 ACOUSTICAL CALIBRATION. The following over -all acoustical calibration can be made with the 1562 Sound-Level Calibrator. This calibration checks the microphone sensitivity as well as the amplifier sensitivity.

Perform the calibration check as described in paragraph 2 .1.2.

Then set the WEIGHTING switch to FLAT. Thrn on the calibrator and set its frequency to 500 cps. Place the calibrator over the microphone. The sound-level meter should read 114±0.5 dB (refer to paragraph 2.2). Switch the calibrator to each of its other frequencies. If the reading of the sound-level meter at 1000 cps is not between 113 and 115 dB, and/or if the readings at the various frequencies vary by more than ± 1 dB, it is possible that the microphone has been damaged; it should then be checked independently.

When the microphone is known to be in good condition, the gain of the sound-level meter can be calibrated by setting the meter reading to 114 dB at 1000 cps by means of the CAL control.

The above calibration will be made free of charge for any GR sound-level meter delivered to one of the General Radio offices listed elsewhere in this manual.

2.2 OPERATING PROCEDURE. a. Turn the instrument on by raising the microphone (battery power) or by turning on the Type 1262-B (ac power). b. Adjust the WEIGHTING switch for the desired frequency response. Refer to paragraph 2. 3. c. Adjust the attenuator switch for an on-scale deflection of the

'ndicating meter. The sound level in decibels is the algebraic sum of he readings of attenuator dial and meter. d. Set the METER-BATTERIES switch to FAST or SLOW depending on the type of meter response desired. The fast response is suitable for most noise measurements and for measuring minimum and maximum values of fluctuating sounds. The SLOW position provides a high degree of damping for measuring the average value of fluctuating sounds.

2. 3 SELECTION OF WEIGHTING NETWORK. Many early noise criteria specified weighted sound levels, using this rule of thumb: A weighting for sound levels from 24 to 55 db, B for levels from 55 to 85 db, and C for levels from 85 to 140 db. (The appropriate range was selected after a preliminary C-weighted measurement.) More recent opinions favor selection of weighting network on the basis of the type of noise measurement; for instance, A weighting is often preferred for speech -interference measurements, while B is recommended for surveys of traffic noise.

In the absence of specific weighting requirements, it is usually helpful to take measurements on all three weighting networks. For a full discussion of weighting networks, refer to the General Radio Handbook of Noise

Measurement. Response curves for the various weighting networks, equalized for microphone response, are given in Figure 3.


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w~ n:~ 0

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-1020

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f--.-+ oVER-ALL FREE-FIELD FREQUENCY RESPONSE r-c WEIGHTING (TO SOUND OF FANDOM INCIDENCE)

50 100 200 500 1000 2000

FREQUENCY IN CYCLES PER SECOND

5000 10,000 20,000

11~51-27'(

+5

0

-5

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-10

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-40

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ELECTRICAL FREQUENCY RESPONSE

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/ FOR THE ASA WEIGHTING CHARACTERISTICS

/

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A

/

/

-45

50 100 200 500 1000 2000


5000 10,000 20,000

~

Figure 3. Typical Acoustical and Electrical

Response Curves for Type 1551-C.

If theSound-Level Meter istobe used withananalyzeror recorder, set the WEIGHTING switch to 20 kc or to C. When an extended-range microphone is used in place of the microphone supplied with the instrument, use the 20 kc position.

2.4 SOUND ANALYSIS AND RECORDING. The low-distortion outputamplifier circuit of the Sound-Level Meter was designed especially for use with the Type 1558-A Octave-Band Analyzer and Type 1564-A Sound and

Vibration Analyzer. Other analyzers, such astheTypel900-A WaveAnalyzer, can also be used. Connect the input of the analyzer or recorder to the OUTPUT phone jack on the Sound-Level Meter. For greatest accuracy, the impedance connected to the output circuit of the Sound-Level

Meter should be about 20,000 to 25,000 ohms. The output impedance is

7000 ohms, and output voltage is 1.1 V into .20,000 ohms, 1.5 V opencircuit. Any load impedance can be connected across the output terminals.

The output system of the Sound-Level Meter can be used to drive a Type 1521 Graphic Level Recorder to obtain permanent records of

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sound measurements, or to operate a magnetic tape recorder to o}:)tain field records that may be studied and analyzed later in the laboratory.

When recording or analyzing, set the attenuator switch so that the meter reads +6 db or more,if possible, to utilize the maximum dynamic range. If the meter reading falls below +6 db, it is sometimes desirable to set the attenuator switch one step lower, even if the meter pointer goes off scale as a result.

The internal calibration system of the Sound-Level Meter makes available, at the OUT jack, the 1000-cycle signal useful for setting the level of an analyzer or recorder to match that of the Sound-Level Meter.

2e5 EXTENSION CABLE. The Type 1560-P73* 25-foot Extension Cable can be used to permit operation of the microphone at some distance from the meter. The extension cable introduces about 7 db loss. For best measurements this cable insertion loss should be determined by calibration with a Type 1562 Calibrator.

2.6 WIDE- RANGE MICROPHONES. The over-all frequency response characteristic of the Type 1551-C,with the WEIGHTING switch set at 20 kc, is essentially flat from 20 cps to 20 kc. (See Figure 4.) This permits use of such wide-range microphones as those used in the Types

1551-PIL and 1551-P1H Condenser Microphone Systems.

The Type 1551-P1L uses the Altec 21-BR-150 Condenser Microphone, useful over the sound-pressure range from 50 to 150 db. The

Type 1551-P1H uses the Altec Type 21-BR-180 Microphone, useful from about 70 to 170 db. (When using the Type 1551-P1L, set the meter to 121 rather than 120 db in the calibration described in paragraph 2.1.3. When using the Type 1551-P1H, set the meter to 101 db and thereafter add 20db to meter readings.) These microphones have a good frequency response from 20 cps to 18 kc.

*Also supplied as part of the Type 1560-P34 Tripod and 25-ft Cable Assembly.

(WEIGHTING SWITCH SET AT 20 Kc)

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20 50

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"\

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100 200 500 1000 2000


5000 10,000 20,000 50,000

Figure 4.

Frequency Response of Type 1551-C Amplifier with WEIGHTING switch at 20 kc.


Also useful with the Type 1551-C over the range from 80 to 200 db is the Massa Type M-141F Standard Microphone, a piezoelectric microphone available from the Massa Laboratories Inc, Hingham, Mass. Its response is reasonably uniform up to 30 kc.

2.7 USE OF HEADPHONES. If desired, a set of headphonescanbeplugged into the OUTPUT jack to monitor the sound being measured.

2.8 BACKGROUND NOISE. When possible, sound measurements should be made with negligible background noise - at least 10 db below the level being measured. However, this is not always possible, and Figure 5 is convenient in determination of errors caused by background noise.

2.9 MICROPHONICS. When high-intensity sound fieldsare being measured, it is good practice to use the microphone on the end of a cable (refer to paragraph 2.5) and to keep the Sound-Level Meter well removed from the sound field. This is especially true if the high-level noise contains frequencies of 1000 cps or higher. The following quick check will determine whether the tubes in the Type 1551-C are beingexcited microphonically: remove the microphone head, set the WEIGHTING switch to

A, and check that there is no meter reading with the attenuator switch set at 70 db or higher.

At sound levels below 140 db no special vibration precautions should be necessary. The amplifier is resiliently mounted, vacuum tubes are resiliently mounted on the amplifier board, the amplifier cover is special- · ly treated to reduce airborne sound transmission, and the instrument sits on soft rubber-feet.

When the Sound- Level Meter, with microphone replaced by an equivalent electrical impedance, is subjected to pure-tone sounds at a soundpressure level of 100 db re 0.0002 ~r and 8000 cps, the output level in each octave band is at least 30 db below that for full-scale meter reading with the attenuator set for 100 db fullscale meter reading.

The Type 1551-C, with its microphone mounted on the panel microphone post, can measure sound pressure levels up to 140 db within the tolerances allowed in ASA Sl.4, 1961. When the microphone is mounted on a cable, the maximum safe sound pressure level for the microphone is 150 db.

Withan auxiliary high-level microphone separated from the Sound-

Level Meter by a long cable to protect meter and operator from intense sound fields, levels up to 200 db can be measured.

2.10 ENVIRONMENTAL EFFECTS.

2.10.1 TEMPERATURE AND HUMIDITY. The Type 1560-P5 Microphone is notdamaged at temperatures from -30°to +95° C and relative humidities from 0 to 100%. When standardized by its internal calibration systern or a Type 1562 Sound- Level Calibrator, the Type 1551-C will operate within catalog specifications (for panel-meter indications above 0 db) over the temperature range from 0 to 60 C and the relative- humidity range from 0 to 80%.

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--

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DB Dl FFERENCE BETWEEN TOTAL NOISE AND BACKGROUND ALONE

Figure 5.

Effect of Background

Noise on Measurement.

+10

+8

+6

!l'l+4

Figure 6. 1 +2 w

Frequency Response as a~

0

Function of Incidence, ~ o::-2

Type 1560-PS Microphone.

-4

-6

20 fPERbENDICJLAR

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~-PARALLEL

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PERPENDICULARJ

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INCIDENCE

RANDOM INCIDENCJ y

1~-

1/

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'

PARALLEL INCIDENCE

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'

100

I

I

1000

FREQUENCY IN CYCLES PER SECOND lopoo

~

The internal impedance of the microphone is capacitive, 475 pf at

25° C, varying from 445 to 510 pf from 0 to 50° C.

2.10.2 VIBRATION. The Type 1551-C case is fitted with soft rubber feet and the amplifier compartment is resiliently mounted for vibration isolation. When set on its rubber feet on a shake table and vibrated over the frequency range of 10 cps to 55 cps, the motion transmitted to the amplifier generates unwanted signals. The magnitude of these signals is listed in the table below. peak-to-peak d i sp I acement

(inches)

0.030

0.010 direction of vibration

X y

Z maximum meter reading(db)

65

45

70

60

55

40


2.10.3 MAGNETIC FIELDS. When exposed to a time-varying magnetic field of 1 oersted, the Type 1551-C will indicate 60 db when oriented for maximum sensitivity to the magnetic field.

2.10.4 ELECTROSTATIC FIELDS. The Type 1551-C is completely enclosed in an aluminum case so that the instrument is not affected by the electrostatic fields which are normally encountered.

2.11 VIBRATION PICKUP. It is often possible to measure the vibration amplitude, velocity, or acceleration of radiating surfaces. Useful vibration measurements can often be obtained where high ambient sound levels make acoustical measurements impossible. For vibration frequencies between 20 and 2000 cps, the Type 1551-C will operate as a vibration meter when used with a Type 1560-PllB Vibration Pickup System. With a Type

1560- Pll S2 Vibration Pickup System (refer to the General Radio Expertmenter, Volume 36, Number 11, November 1962), the Type 1551-C can be used for vibration measurements between 20 and 10,000 cps.

Refer to the General Radio Handbook of Noise Measurement for further information on vibration measurements.

Section 3

CALIBRATION

3.1 GENERAL. The calibration (acoustical and electrical) of the Type

1551-C Sound-Level Meter is carried out with pure tones. The Sound-

Level Meter calibration is adjusted for random incidence sounds with the microphone mounted on the panel microphone post.

Microphone calibrations are made at 0 degrees (perpendicular incidence) in a free field with the microphone at the end of a cable. All microphone calibrations supplied by General Radio are at 0 degrees incidence. A correction curve is supplied to convert from 0 degrees to random-incidence response.

3.2 OBSERVER INFLUENCE. When measurements are made in reverberant or semireverberant fields, the observer and Sound- Level Meter case have a very small effect on the microphone response. Under freefield conditions and with a single sound source, both the observer and the case can have a large effect on microphone response (refer to the General

Radio Handbook of Noise Measurement). These effects can be minimized if the instrument is held in front of the observer, with the observer oriented so that the sound passes in front of him at right angles to the axis of the Sound-Level Meter and its microphone.

For greatest accuracy it is recommended that the microphone be mounted on a tripod and connected to the Sound- Level Meter by an. ex tention cable to keep the observer and the meter case out of the sound field being measured.

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3.3 PREFERREDANGLEOFINCIDENCE. When measurementsarema e on sounds in reverberant fields, the angle of incidence of sounds reaching the microphone is indeterminant. In this case there is no preferred angle of incidence between the microphone and the sound source. When measurements are made on a source in a free field, an angle of incidence of

70degrees between the axis of the microphone and the sound source will approximate random response.

3.4 AUXILIARY CALffiRATION. The Type 1551-C has an internal calibrating system for quick checks on the electrical circuit of the instrument. This system connects the output of the amplifier to the input through an appropriate attenuator, filter, and limiter to produce a predetermined oscillation amplitude when the amplifier gain is correct. This system checks the electrical operation only and does not check the microphone.

To make an acoustical check on the calibration of the instrument, the

Type 1562 Acoustic Calibrator is recommended. -This is a closed coupler with a driving loudspeaker that produces aknown sound pressure level at the microphone.

3.5 METER CIRCUIT. The metercircuitusedin the Sound-Level Meter,. while not a true rms indicator, indicates much more closely to the rms value than have meters in earlier instruments. The meter circuit comhines an average-reading circuit with a peak-reading circuit to create a

"quasi-rms" indicating circuit. Since the rms value of most waveforms falls above the average value but below the peak value, a porti.on of the peak indication added to the average value of a given waveform should result in an rms indication. The meter circuit is designed to approximate rms values for various types of waveforms.

Table 2 below shows the db difference between the indication of a true rms meter and that of the Type 1551-C Sound-Level Meter for several test signals. In the column headed "db Fluctuation . . . . . etc" the signal consists of two tones, one at 1000 cps set for a convenient meter indication. The other tone is within a few cycles of 3000 cps and has 30 percent of the amplitude of the first. A true rms meter will showno fluctuation with this type of signal. The column headed "For Two-Signal Addition"l"efersto the two-signaltestoutlined in ASA Standard Z24.3-1944.

With pulses of constant height but varying length, the Type 1551-C

Sound-Level Meter indicates the rms- value within ±1 db until the pulse duration becomes as short as 1/25 that of a square wave.

TABLE 2.

Type

Meter

1551-C db Fluctuation with Phase Changes at 30% 3rd Harmonic

0.45

Difference in Meter Indication and RMS

Decibels

For

Two-Signal

Addition

For

Square

Waves

For

Noise

+.05 +0.1 -0.25

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Section

SERVICE AND MAINTENANCE

4.1 GENERAL. Wewarrant that each newinstrument manufactured and sold by us is free from defects in material and workmanship, and that, properly used, it will perform in full accordance with applicable specifications for a period of two years after original shipment. Any instrument or component that is found within the two-year period not to meet these standards after examination by our factory, Sales Engineering Office, or authorized repair agency personnel, will be repaired, or, at our option, replaced without charge, except for tubes or batteries that have given normal service.

The two-year warranty stated above attests the quality of materials and workmanship in our products. When difficulties do occur, our service engineers will assist in any way possible. If the difficulty cannot be eliminated by use of the following service instructions, please write or phone our Service Department (see rear cover), giving full information of the tr-ouble and of steps taken to remedy it. Be sure to mention the serial and type numbers of the instrument.

Before returning an instrument to General Radio for service, please write to our Service Department or nearest Sales Engineering

Office, requesting a Returned Material Tag. Use of this tag will ensure proper handling and identification. For instruments not covered by the warranty, a purchase order should be forwarded to avoid unnecessary delay.

4.2 REMOVAL OF INSTRUMENT FROM CABINET. To remove the instrument from its cabinet, remove the two large black screws from the bottom of the cabinet and lift the cover off.

4.3 TUBE F AlLURE. As tubes age, one or more of them may become open -circuited. Check the filament resistance with an ohmmeter between pins Band 5 of the tube base (see Figure 8). Make sure that the ohmmeter current through the filaments is less than 10 rna.

4.4 TUBE REPLACEMENT. Foraccess to tubes,removethetwoPhillipshead screws that attach the cover of the amplifier compartment, and lift off the cover. The tubes are held in place between rubber pads on the amplifier shelf and on the inside of the cover.

When replacing a tube, cut the leads on the new tube to between

5/16 and 3/8 inch before inserting the tube in the socket. Install the tube so that the red dot on the tube base is on the same side as that on the socket.

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4.5 BATTERY REPLACEMENT. To replace any of the batteries, remove the black screw that secures the holding bracket. (See Figure 9.)

After the bracket is removed, the batteries can be withdrawn and replaced. Observe proper polarity as marked, when replacing batteries.

4.6 REPLACEMENT OF BIAS CELL. For access to the bias cell~ remove the two studs and washers from the ends of the amplifier etchedcircuit board. Pivot the amplifier shelf upward to expose the bias cell.

To remove the bias cell, first pull the contacting clip sideways and away from the bias cell The bias cell can then be unscrewed and replaced.

When returning the amplifier shelf to its original position, be careful that all wires are free and that none will be pinched between shield and chassis.

4.7 SOLDERING OF CONNECTIONS TO CABLE WIRES. The plastic insulation on the wires in cables and on many interconnecting leads melts easily, and extreme caution is advised in soldering connections. If the wire is held with pliers near the spot to be soldered, heat will be carried away from the insulation, helping to avoid melted insulation.

4.8 MICROPHONE SENSITIVITY ADJUSTMENT. An internal sensitivity control is adjusted in the General Radio laboratory to match the characteristics of the microphone sent with each meter. If a microphone with a different sensitivity is substituted for that furnished, set this adjustment (see Figure 9) to indicate the new microphone sensitivity. Also, a check of acoustical calibration should be made by the method outlined in paragraph 2.1.3.

4.9 INTERNAL NOISE. Internal noise should not normally affect readings with the attenuator switch set at 40 or higher. If desired, the following procedure can be used to determine how much noise is generated in the mstrument. Remove the microphone, and connect a 380-pf capacitor across terminals 1 and 3 of the microphone socket. This capacitor and its connecting leads must be completely shielded in a metal can connected to either the metal part of the microphone socket or to terminal

1, which is grounded. The connection is identical to that shown in Figure 7, except that a short circuit replaces the oscillator.

SOUND-LEVEL

METER

INPUT CONNECTOR

USE C-WEIGHTING

NETWORK lt551-28!

Figure 7. Circuit for Calibrating Amplifier Gain.

Be certain that there is no external pickup of any stray fields. The meter on the instrument should not read above -6 with the attenuator

12


switch set at 30, the WEIGHTING switch at C, and the METER BATTER-

IES switch at FAST.

Internal noise can be caused by the bias cell, B50, or by the batteries. Tube noise is generally caused only by V50 or V52, which can be interchanged with V51 or V53 or replaced if less noise is required. It may be necessary to try several tubes to achieve a satisfactory reduction in noise. Typical noise levels arc given in the following table.

TYPICAL INTERNAL SIGNAL-TO-NOISE RATIOS

C WEIGHTING

(db BELOW FULL SCALE· SET FOR -60 db MICROPHONE)

1551-C

Attenuator

Setting db

All Pass

20 cps·

20 kc

NOISE LEVELS· db

OCTAVE BAND· cps

31.5 63 125 250 500 1000 2000 4000 8000 16000

30

40

50

60

70

80

90

100

110

120

130

140

17

27

37

46

52

54

55

55

54

55

55

55

25

35

45

55

64

73

78

80

79

80

79

80

26

36

46

56

64

28

38

48

58

67

73 74

77

77

78

78

76

76

78

78

76

77

77 78

30

40

50

60

68

74

75

76

73

76

75

76

30

41

51

61

68

73

73

74

71

74

73

74

67

71

71

71

30

40

50

60

69

71

70

71

28

38

48

58

65

68

68

68

67

68

68

68

26

36

46

56

63

65

66

66

65

66

66

66

27

37

47

56

62

63

63

63

63

63

63

63

29

39

. 48

57

59

60

60

60

60

60

60

60

4.10 AMPLIFIER GAIN. With the Sound-Level Meter set for normal operation with C weighting, apply a 1.0-volt, 400- or 1000-cycle signal to the microphone socket through a shielded 380-pf capacitor, as shown in Figure 7. The meter reading should agree with that given below for the sensitivity of the microphone used, (Microphone sensitivity ls listed at the front of this manual, as well as on a label inside the instrument.)

1560-P3 (981Ul:S}

Microphone Sensitivity db re 1 volt/ubar

-62

-61

-60

-59

-58

-57

Type 1551-C reading

136

135

134

133

132

131

4.11 TEST VOLTAGES AND RESISTANCES. The table on the following page lists de voltages and resistances between tube and transistor pins and ground, as measured with a vacuum-tube voltmeter. For voltage measurements, set the attenuator to 130 CAL, the WEIGHTING switch to

A, and the METER-BATTERIES switch to FAST. For resistance measurements, remove batteries and ground terminals 2, 3, and 4 of socket 802.

13


14

TABLE OF VOLTAGES AND RESISTANCES.

TUBE

(TYPE)

PIN

FUNC-

TION

VOLTS DC RES

BTRY 1262-B TOGND

V50

(CK512AX)

V51

(CK512AX)

V52

(CK512AX)

V53

(CK512AX)

V54

(CK6418)

V55

(CK6418)

TRI

(2Nl372)

RX51

S02

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

1

2

3

4

5

K

4 p s c

G c p 15.0 15.5 890 k s

15.0 15.5 890 k c

0.71 0.7 16

G c

-1.40

0

-1.41

0

*

0

16.0

14.1

1.45

0

0.72

16.1

14.2

1.41

0

0.71

320 k

940 k

0

1M

16 p s c

G c

9.4

9.4

0.76

-0.48

0

9.1

9.1

0.76

-0.48

0 p 21.5 20.5 s

14.9 14.3 c

1.44 1.4

G c

0

0.76

0

0.73

850 k

850 k

16

18M

0

340 k

1.21 M

0

18M

16 p s c

G c p 17.2 16.3 123 k s

17.6 17.0 400 k c

1.48 1.42 0

G c

-0.35

0

-0.35

0

18M

0

14.5

21.5

1.47

-0.22

0

13.9

20.7

1.37

-0.22

0

100 k

270 k

0

18M

0

E

B c

14.3

14.2

0

40.2

65.0

13.0

12.9

0

39.7

59

30 k

-

-

96 k

0

*Do not attempt to measure (bias cell in circuit).


Ref. No. Description

PARTS LIST

GR

Part No.

Fed. Mfg.

Code

Mfg. Part No.

Fed. Stock

No.

CAPACITORS

Cl Mica, 330 pF ±2% 500 V

C2

C3

1 c. 4 pF

Trimmer, 7 - 45 pF

Mica, 30 pF ±2% 500 V C4 cs

C7

C59

C60

C61

C62

C63

C64

C65

C66

C67

C68

C52

C53

C54

C55

C56

C57

C58

C69

C70

C71

C8

C9

C10

C11

C12

C13

CIS

C16

C19

C20

C21

Mica, 90.0 pF ±2% 500 V

Plastic, 0.0033 j..LF ±2% 200 V

Mica, 178 pF ±2% 500 V

Mica, 178 pF ±2% 500 V

Plastic, 0.0332 j..LF ±2% 100 V

Mica, 220 pF ±2% 500 V

Wax, 0.4 7 1-LF ±10% 100 V

Electrolytic, 60 1-LF 25 V

Ceramic, 12 pF ±5% 500 V (NPO)

Mica, 35 pF ±2% 500 V

Mica, 0.001 f.LF ±5% 500 V

Mica, 0.001 f.LF ±5% 500 V

Mica, 0.0012 j..LF ±5% 500 V

C22 Mica, 0.001 f.LF ±5% 500 V

C23 Plastic, 0.00158 j..LF ±1% 200 V cso

Wax, 0.1 1-LF ±10% 100 V

CSI Wax, 1 1-LF ±10% 100 V

Electrolytic, 50 f.LF 50 V

Wax, 0.22 1-LF ±10% 100 V

Wax, 0.1 1-LF ±10% 100 V

Wax, 0.22 1-LF ±10% 100 V

Wax, 0.22 f.LF ±10% 100 V

Electrolytic, 30 j..LF 100 V

Wax, 0.01 1-LF ±10% 100 V

Wax, 0.1 1-LF ±10% 100 V

Wax, 0.1 1-LF ±10% 100 V

Wax, 0.01 1-LF ±10% 100 V

Wax, 0.22 1-LF ±10% 100 V

Wax, 0.47 1-LF ±10% 100 V

Plastic, 0.0606 j..LF ±2% 100 V

Wax, 1 1-LF ±10% 100 V

Wax, 0,04 7 1-LF ±10% 100 V

Wax, 0.4 7 1-LF ±10% 100 V

Wax, 0.4 7 1-LF ±IO% 100 V

Wax, 0.4 7 1-LF ±10% 100 V

Electrolytic, 19 j..LF 150 V

Ceramic, 3.3 pF ±10% 500 V

4690-3200 00656 CM20E, 300 pF ±2%

1551-0420 24655 1551-0420

4910-0100 72982 T8AN300, 7-45 pF

4690-(1400 00656 CM20E, 30 pF ±2%

5905-858-4049

5910-799-9275

4690-1201 00656 CM20E, 90.9 pF ±2%

4860-7350 84411 663UW, 0.0033 1-LF ±2%

4690-2217 00656 CM20E, 178 pF ±2%

4690-2217 00656 CM20E, 178 pF ±2%

4860-7868 84411 663UW, 0.0332 f.LF ±2%

4690-2700

·5010-3600 80183 78P4 74183

4690-(1600

5910-448-5765

4450-2900 56289 D17872

4400-3200

5910-799-9280

00656 Type CL-1, 12 pF ±5% 5910-705-6442

00656 CM20E, 35 pF ±2% 5910-731-1750

4580-(1100

00656 CM20E221G

14655 SA, 0.001 1-LF ±5%

4580-0100 14655 SA, 0.001 f.LF ±5%

5910-931-4153

5910-052-7016

5910-052-7016

4580-(1200 14655 SA, 0.002 1-LF ±5%

4580-(1100 14655 SA, 0.001 1-LF ±5%

4860-7319 84411 663UW, 0.00158 f.LF ±1%

5010-2700 56289 78Pl049183

5010-3700 80183 78P1057183

4450-2200 80183 50 1-LF +100-10%

5010-3300 80183 78P2241183

5010-2700 56289 78P1049183

5910-052-7016

5910-448-5758

5910-:615-5-255

5910-799-9283

5910-448-5777

5910-448-5758

5910-448-5777

5910-448-5777

5910-708-5191

5010-3300 80183 78P2241183

5010-3300 80183 78P2241183

4450-1900 37942 9594 7G7823Cl0X3

5010-1600 80183 78Pl031S3

5010-2700 56289 78P1049183

5010-2700 56289 78P1049183

5010-1600 80183 78P103183

5010-3300

5010-3600

80183 78P2241183

80183 78P474183

4860-8213

5010-3700

84411 663UW, 0.0606 f.LF ±2%

80183 78P1057183

5010-2100 56289 78P4 73183

5010-3600 80183 78P474183

5010-3600 80183 78P4741S3

5010-3600 80183 78P474183

4450-(1200 37942 D33104

4400-(1400 78488 GA, 3.3 pF ±10%

5910-448-5788

5910-448-5758

5910-448-5758

5910-448-5788

5910-448-5777

5910-448-5765

5910-615-5255

5910-448-5765

5910-448-5765

5910-448-5765

5910-829-3313

5910-708-5197

RESISTORS

R1 Film, 22.'J MQ ±1% 1 W

R2

R3

R4

Film, 2.17 MQ ±1% 1/2 W

Film, 333 kQ ±I% 1/8 W

RS

R6

R7

R8

R9

RIO

*R18

R20

R21

R23

R24

R25

R26

R27

R28

R29

R30

R31

R32

R33

R34

R35

R36

R37

*R38

R39

R40

Rll

Rl2

R13

R14

RIS

R16

R17

Film, 1.0 MQ ±1% 1/8 W

Film, 659 kQ ±1% 1/8 W

Film, 73,2 kQ ±1% 1/8 W

Film, 500 kQ ±1% 1/8 W

Film, 159 kQ ±1% 1/8 W

Film, 108 kQ ±1% 1/8 W

Film, 50 kQ ±1% 1/8 W

Composition, 3 kQ ±5% 1/2 W

Film, 16.9 kQ ±1% 1/2 W

Film, 16.9 kn ±1% 1/2

·w

6182-5229

6450-4217

6250-3333

6250-4100

6250-3659

6250-2732

6250-3500

6250-3159

6250-3108

6250-2500

6250-3154

6250-2159

6250-3169

03888 PT1000, 22.9 MQ ±1%

75042 CEC, 2.17 MQ ±1%

75042 CEA, 333 kQ ±1%

75042 CEA, 1 MQ ±1%

75042 CEA, 659 kQ ±1%

75042 CEA, 73.2 kQ ±1%

75042 CEA, 500 kQ ±1%

75042 CEA, 159 kQ ±I%

75042 CEA, 108 kQ ±I%

75042 CEA, 50 kQ ±I%

75042 CEA, 154 kQ ±1%

75042 CEA, 15.9 kQ ±1%

75042 CEA, 169 kQ ±1%

Film, 154 kQ ±1% 1/8 W

Film, 15.9 kQ ±1% 1/8 W

Film, 169 kQ ±1% 1/8 W

Film, 7.32 kQ ±1% 1/8 W

Film, 63.3 kQ ±1% 1/8 W

Film, 216 kQ ±1% 1/8 W

Film, 100 kQ ±I% 1/8 W








6250-1732

6250-2633

6250-3216

6250-3100

6100-4105

6100-4115

75042

75042

75042

75042

CEA, 7.32 kQ ±1%

CEA, 63.3 kQ ±I%

CEA, 216 kQ ±I%

CEA, 100 kQ ±I%

01121 RC20GF104J

01121 RC20GF114J

6100-3755 01121 RC20GF753J

6100-4625

6100-2305

01121 RC20GF624J

01121 RC20GF302J

6100-3115 01121 RC20GF113J

6100-2305 01121 RC20GF302J

6100-2305 01121 RC20GF302J

6250-2169 75042 CEA, 16.9 kQ ±1%

6250-2169 75042 CEA, 16.9 kQ ±1%

Composition, 820 kQ ±5% 1/2 W 6100-4825 01121 RC20GF824J




6100-3205 01121 RC20GF203J

6100-3435 01121 RC20GF433J


Potentiometer, composition 50 kQ ±10% 6010-1400 01121 JU, 50 kQ ±10%

6100-4335 01121 RC20GF334J



Potentiometer, composition 100 kQ ±10% 6010-1700 01121 JU, 100 kQ ±1%

Potentiometer, composition 100 kQ ±20% 6040-1000

Comp9sition, 1.0 MQ ±5% 1/2 W 6100-5105

01121

01121

FWC, 100 kQ ±20%

RC20GF105J

5905-646-5678

5905-655-1982

5905-783-8446

5905-8 92-6921

5905-578-0994

5905-577-6743

5905-195-6761

5905-279-1867

5905-2 79-3495

5905-221-5841

5905-279-1751

5905-279-2667

5905-279-1751

5905-279-1751

5905-806-8487

5905-806-8487

5905-221-5848

5905-192-0649

5905-279-3498

5905-279-1878

5905-055-3046

5905-279-2519

5905-279-1878

5905-279-3496

5905-797-1054

5905-958 -7949

15905-192-0390

15


PARTS LIST {Cont)

R69

R70

R71

R72

R73

R74

R75

R76

R77

Ref. No. Description

RESISTORS (Conti

*R50 Composition, 430 kQ ±5% 1/2 W

R51

R52


Film, 1 MQ ±1% 1/8 W

R53

R54

R55



Film, 290 kQ ±I% 1/8 W

*R56

*R57

R58

R59

*R60

R61

R62

R63

R64

*R65

Composition, 18 MQ ±5% 1/2 W

Composition, 750 kr.l ±5% 1/2 W




Composition, 1.2 MQ ±5% 1/2 W





R66

*R67

R68

GR Fed. Mfg.

Part No. Code

6100-4435 01121

6100-4115 01121

6250-4100 75042

6100-4915 01121

6100-3335 01121

6250-3290 75042

6100-6185 01121

6100-4755 01121

6100-4105 01121

6100-6185 01121

6100-4685 01121

6100-5125 01121

6100-4335 01121

6100-6185 01121

6100-4395 01121

6100-4115 01121

Potentiometer, composition 2.5 kr.l ±10% 6040-1700 01121

Composition, 300 n

±5% 1/2 W


6100-1305 01121

6100-3105 01121



Composition, 2.4 MQ ±5% 1/2 W







6100-4225 01121

6100-6185 01121

6100-5245 01121

6100-4305 01121

6100-4105 01121

6100-4125 01121

6100-4475 01121

6100-3105 01121

6100-3205 01121

MISCELLANEOUS

Bl

B2

B3

B50

01

02

03

04

05

Battery, 1 -1/2 V Type D cell

Battery, 1-1/2 V TypeD cell

Battery, 67-1/2 V

Battery, 1-1/2 V

Diode, type 1N34A (S)



Diode, type 1N34 A (S)

Diode, type 1N645

06

Jl

Ml

PLl

Ql

Diode, type 1N645

Jack

Meter, 100 fla de

Plug

Transistor, type 2Nl372

RX51 Diode, type 1N967B

S1

S2

Switch

Switch

S3

S4

SOl

S02

V50

Switch

Switch,DPST

Socket

Socket

V51

V52

V53

V54

V55

Tube

Tube

Tube

Tube

Tube

Tube

8410-D200 77542

8410-D200 77542

8410-2300 09823

4020-DlOO 90303

6082-1003 82389

6082-1003 40931

6082-1003 71785

6082-1003 58854

6082-1016 58854

6082-1016 58854

4260-1500 58854

5730-1050 24446

24446

8210-1372 86800

6083-1020 76854

7890-1600 76854

7890-1600 24655

7890-1530 24655

1551-D450 24655

4230-2840 71785

4230-3500 01295

8370-1400 94144

8370-1400 94144

8370-1400 94144

8370-1400 94144

8380-6418 94144

8380-6418 94144

*Must be Allen-Bradley.

Mfg. Part No.

2LP

2LP

XX45

BC4

#111

MEDS-105

P-302-AB

IN34A(S)

IN34A(S)

IN34A(S)

IN34A(S)

IN645

IN645

IN976B

179901-H4C

179901-H4C

7890-1530

1551-0450

4230-2840

S-306-AB

2Nl372

CK512AX

CK512AX

CK512AX

CK512AX

CK6418

CK6418

RC20GF434J

RC20GF114J

CEA, lMO ±1%

RC20GF914J

RC20GF333J

CEA, 290 kr.l ±1%

RC20GF186J

RC20GF754J

RC20GF104J

RC20GF186J

RC20GF684J

RC20GF125J

RC20GF434J

RC20GF186J

RC20GF394J

RC20GF114J

FWC, 2500 Q ±10%

RC20GF301J

RC20GF103J

RC20GF224J

RC20GF186J

RC20GF245J

RC20GF304J

RC20GF104J

RC20GF124J

RC20GF474J

RC20GF103J

RC20GF203J

Fed. Stock

No.

5905-279-2518

5905-279-1867

5905-646-5678

5905-221-5853

5905-171-1998

5905-279-2503

5905-279-1759

5905-195-6761

5905-279-2503

5905-171-2000

5905-190-8874

5905-279-2518

5905-279-2503

5905-279-2517

5905-279-1867

5905-279-5481

5905-185-8510

5905-192-0667

5905-279-2503

5905-279-2512

5905-185-6859

5905-195-6761

5905-192-3981

5905-279-2515

5905-185-8510

5905-192-0649

6625-708-5186

5961-170-4430

5961-170-4430

5961-170-4430

5961-170-4430

5961-944-8222

5961-944-8222

5960-854-8469

5930-708-5199

5930-708-5198

5960-581-9593

5960-581-9593

5960-581-9593

5960-581-9593

5960-537-3967

5960-537-3967

Fig. 8

Ref.

4

5

6

Name

Microphone

Knob Asm.

Knob Asm.

Thumbset

Support

Knob Asm.

8

(Hidden)

9

Meter Cover*

Foot

Handle

MECHANICAL PARTS LIST

Description

GR

Part No.

Fed. Mfg.

Code Mfg. Part No.

Piezoelectric -Ceramic

Knob, attenuator; includes bushing 4140-0300

Knob, WEIGHTING; includes bushing 4140-0300

CAL control

Black rubber

Knob, METER/Batteries;

1560-9605

5530-1200

5500-0400

5540-2500

5260-1600 includes bushing 4140-0300 5500-0400

ME3-701 Cover; Dark Gray Mask 5720-3712

Block rubber 5250-1902

Leather strap handle 1551-0460

*When ordering, please specify manufactured by Weston or Honeywell.

24655 1560-9605

24655 5530-1200

24655 5500-0400

24655 5540-2500

24655 5260-1600

24655 5500-0400

24655 5720-3712

24655 5250-1902

24655 1551-0460

Fed. Stk.

No.

5355-926-5196

5355-051-6594

5355-051-6594

16



---·

7

6

Figur e 8. External mechanica l po rt s of the

Sound-Level Meter.


en

()

r:Y

o"'

06

Oo/

( )

~':!

MARKING FOR

S-1 DIAL 8 KNDB

S-2

ENGRAVING

S-3

ENGRAVING

V50

V51

V52

V53

RAYTHEON

S S I

REO

007

V54

V55

JRANSISTORS

()/

Rotary switch sections are shown as vi•w•d from th• panel end of th• shaft. Th• first digit of th• contact number r•f•rs to th• section. Th• s•ction n•orest the pan•l is 1, th• n•xt section bock is 2, •tc. Th• n•xt two digits ref•r to th• contact. Contoct 01 is the First position clockwi .. from o strut screw (usu-

•lly th• scr•w oboveth•locating k•y), ond the oth•r contocts or• numb•r•d uqu•ntially (02, 03, 04, etc), proc•eding clockwiu around th• sect;on. A suffix

F or R indicatu !hot th• contact is on th• front or rear of th• uction, r•spectiv•ly.

NOTE.-

R£SISTORS 1/2 WATT UNLESS OTHERWISE SPE

RESISTANCE IN OHMS UNLESS OTHERWISE

K=IOOO OHMS M=IMEGOHM

CAPA Cl TANCE VALUES ONE 8 OVER IN MICRO

LESS THAN ONE IN MICROFARADS UNU

OTHERWISE NO TED.

@ SCREW DRIVER AO./USTMENT

Q

PANEL CONTROL


5

R31

20K

R32

43K

R33

24K

Cl9

001

S-2

ENGRAVING

S-3

ENGRAVING

CABI.E

"an"

/( C52:..J!T+

50pf

50v

R54

33K

NOTE:

RESISTORS 1/2 WATT UNLESS OTHERWISE SPECIFIED

RESISTANCE IN OHMS UNLESS OTHERWISE SPECIFIED

K, 1000 OHMS M, I MEGOHM

CAPACITANCE VALUES ONE 8 OVER IN MICRO' MICROFARAOS,

LESS THAN ONE IN MICROFARADS UNLESS

OTHERWISE NOTED.

@ SCREW DRIVER ADJUSTMENT

Q PANEL CONTROL

R68

IOK

'----4

R72

300K

Figure 9. Schemati

Type 1551-C Sound-L


C/9

001

O(V~~ OFF

Wv---

R31

20'1< """

6

'

<JI' 54

R33

24K

R32

43K

~

<I 2 ..

,

.......

·

~

--

81 82 ,:!!!:83

WH-8H~PPi·#L -~ H~G>'

1

"'"

-r-~1Cf<f1 ~ 02

-~=·~

~==~~~~==~~~~~-~~~~~~~~~~~~-~-1

CABLE

"n~

I

I[

I I

1

[I

I

1

11 vr (f'lc;..

~<J

" /

I

·~a

·.

2~

I

I'

I[ llt06F

-~~

. l1

112

F-'6'11.9V\Kr-'-

,t~~

R29

1 o~t"-f'

R30

_ _

04

JJ!T • • -:-"::o:!or_.._~

1ou r1.

1~2F

J...

·WH-8L-8K

_:::.~~

. .

L

~

R/6 I

~

-~ ·

"

•o•"

216K 1 t/8w t/8w 1

~

R/7 lOOK

I/8W

I

I

~I

CABLE"wH".:.-1

I

I

11

11

:: li /

I[

I I

I

I f---g--:'1!.~-----='-

£1~~~

~¥ j~l

0,. •

,....

~ aR-

H.l---!oa:"-:" .

C/1

220·

J05R

6%~

, I _ - - - - - -

R21

7.51<

""'fruR if+ /

I

~

'

,-

1 -

J;.

Jl,-

3!.-

-ll

[I

,IJj

I!

\

CABU"OR' \ \

rit \\

l.

ct6 ,..

.

I

&&ik

a

0"

20>R il

~ ~~

~ ~I /Y!K

.~~I

i

[[

I

II

11

II lTI CAsali

'"Ci

Afl li

I[

I[

_jdJ

20...

II

II lj

I

II

---·1

.

I

C

I/78

~

8 our

~: 3 /f lK~

~ 3 --'W'r---'JJ,j?

.~pzf -~R26

K ..

~I

~};

4 l3K

J.(

C/3 l60sd

.-K i/

WH-811-!IJI

4 _ ·

I

. ' .

/04R lOTH

l&-+

·

j

I

I

WH•IfD

w ·

~-

53

WH-vr

~

.

WH-OR

II-

! I

WH GH·BR ""E="

--- -- - - -- --

~-

-llm---l

~-c;--

-- -- -;;- _-_-

--1 c:;* J~~* :::~r:/

f%7--=-------,

C60

.I 11 ~

V53 R62 1\.01

r:~3~K

RIH

'cs.if::: '

./ R61

!.2M

18M

~- ,1~;.

20 GY

~24M tCb~

'

'Ci2

8

"

~

,-;rf

2

.~:.:~;;gO

18

J -

5 5

' -;

C67

.47 R64

390~

R67

300 u

R74

120K

R68

IOK

'-----<

R72

300K

R75

~

R76

-

!OK

470K ~

R77

20K

Figure 9. Schematic Diagram,

Type 1551-C Sound-Level Meter.

17


S.•:tior

TYPE 1262-11 f'OWE~ SUPPlY


Figure 10.

Interior View, T ype 1551

Sound-Level Meter.

18

F i gure 11. Componen t Layout on Etched Boord .

Complete board i s PIN 1551-2201.

NOTE

T he nu m be r shown on t h e foil side of the b oa rd i s n ot t h e part number for the complete assem bl y. The assembly n u mber is given in the cap ti on .

R77

R75

I

BLOCK


Figure 10 . erior View, Type 1551-C

Sou n d-Level Meter .

BLOCK DIAGRAM

Figure 12.

Elementary Block l


MICROPHONE

SENSITIVITY

ADJUSTMENT

Figure 12

~~:~:: .

Elementary Blo c k Diag r am.

R50

C51

R51

5.1 Il' movet andre saryfi the tw• cover to th e of the

Th e s : the reo

5 .

2 0

210-2

Sound·

Sound· is batt

BATT1 meter

5.3 81

5.4 N depenc

Supply nents : weight orB w voltag weldeJ listed


Section 5

TYPE 1262-B POWER SUPPLY

5.1 INSTALLATION. Before using the Type 1262-B Power Supply, remove the batteries from the Sound-Level Meter(refer to paragraph 4.5), and replace the Sound- Level Meter in its case.

To attach the power supply to the Sound-Level Meter, it is necessary first to remove the cover from the power supply. To do this,loosen the two 10-32 screws at the ends of the power supply. Then slide the cover off, i.e., away from the engraved panel of the pCNler supply.

Two 1/4-28 binder-head screws are used to attach the power supply to the Sound-Level Meter. Insert these screws through holes in the back of the power supply and mating threaded holes in the Sound-Level Meter.

The six-terminal male connector in the power supply should slip into the receptacle on the Sound-Level Meter.

5.2 OPERATION. Connect the Type 1262-B input plug to a 105-125 (or

210-250) -volt, 50- 60-cycle power source. Turn the Power Supply and

Sound-Level Meter on by means of the power supply on-off switch. (The

Sound-Level Meter's on-off switch functions only when the instrument is battery-operated.) To check for proper operation, setthe METER-

BATTERIES switch to PL and FIL, checking that for each position the meter pointer falls within the white BAT area on the meter face.

5.3 SERVICE AND MAINTENANCE. Refer to pa\ragraph 4.1.

5.4 NOISE LEVEL. The internal noise level of the Sound- Level Meter depends on the quality of the power line supplying the Type 1262-B Power

Supply. With a good line (i.e.~ no transient humps or frequency components below 50 cps), the noise level will be 28 db or less for the 20-kc weighting position, below 26 db with C weighting, and below 24 db with A or B weighting.

If the Sound-Level Meter is operated in an area where the line voltage fluctuates abruptly and repeatedly (e.g. near devices such as spot welders), the internal noise level will appear to be higher than thevalues lusted above.


1262-B P"AitTS liST

ClR Fo<!Mfg_

---~ ~-----

•J4jft

---i---.-.-

f~-


Ref. No.

CAPACITORS

CIA

C1B

C2A

C2B

C2C

C3A

C3B

C3C

C4A

C4B

Description

Electrolytic, 300 flF 35 V

1200


1200

200

Electrolytic block, 100 flF 100 V

100


1262-B PARTS LIST

GR Fed, Mfg.

Part No. Code Mfg. Part No.

4450-2400 37942 2021149S4Cl0Xl

4450-4200 37942 20-21339-99-6

4460-1500 80183 DFP, 200/100/100 flF

4450-2400 37942 2021149S4Cl0Xl

PILOT LAMP

P1 115V 8390-0600 24446 NE-51

RESISTORS

Rl

R2

R3

R4

R5

R6

R7

R8

R9

RIO

Rll

Composition, 100 kn ±5% 1/2 W

Composition, 200 n ±5% 1/2 W





Composition, 1.5 kn ±5% 1/2 W

Composition, 1.5 kn ±5% 1/2 W

Composition, 51 kfl ±5% 1/2 W



RECTIFIERS

RXl

RX2

RX3

RX4

RX5

SWITCH

Sl Toggle

6100-4105 01121 RC20GF104J

6100-1205 01121 RC20GF201J

6100-1135 01121 RC20GF131J

6100-0435 01121 RC20GF430J

6100-0475 01121 RC20GF470J

6100-1185 01121 RC20GF181J

6100-2155 01121 RC20GF152J

6100-2155 01121 RC20GF152J

6100-3515 01121 RC20GF513J

6100-1225 01121 RC20GF221J

6100-1435 01121 RC20GF431J

6080-2800 77638 2J9

6080-2700 77638 6YI

6080-2900 77638 6J2

6080-2500 77638 IYI

6080-2600 77638 3YI

7910-1300 04009 83053-SA

TRANSFORMER

T1 0746-4310 24655 0746-4310

Fed. Stock

No.

5910-822-2691

5910-822-2692

5910-822-2691

62 40-223-9100

5905-195-6761

5905-279-2674

5905-252-5436

5905-279-1887

5905-252-4018

5905-279-3514

5905-841-7461

5905-841-7461

5905-279-3496

5905-279-3513

5905-279-3512

5930-909-3510


RESISTORS 1/2 WATT UNLESS OTHER W ISE

~~F~a

ReSISTANCE IN OHMS UNLESS OTHERWISE

SPECIFIED

K1000 OHMS

CAPACITANCE VALUES I N NICRCFARA OS

UNLESS OTHEHWISE SPECIFIED

T·l

~ ~ --.~ ---.----~~-~ ~---------

INPUT

115r. OR 2J0fl.

50fiOc .

R3

IJD

112

200

R4

4J

C · 18

1 3 00

0

I~;

FOR 230v. INPUT CONNECT #2 T O I>:J

F i gu re 14 . Lay ou t of C om pone n t s on Et ched Boord .

F i g u r e 1 3 . S ch e ma ti c D iagra m , Typ e

R£CTIFIE~

I

·•

FI LTE R f

"

~ f

: ReCTIFIER idh *~ j

~

RECTIFIER j

~


A4

"lC-48

1 3 0 0

~~+ RX-5

A3 y~

R6

/80 l>

R4

43

C-18

300

AI

0

R5

47

C-2A

1200

=;;:~j;gg

A6

:~

RX-3

~

..-IUD

__j+

I

R8

1.5K c

;;:

C-38

IOU

";;: C-3C

100

R!J

51K

A2

GY

VT c

C-2C

' 1200

RO

~.; l

-,

: c Diagram, Type 1262-B Power Supply.

';TIF!ER

••

FILTER

RECTIFIER

VOLTAGE

LIMITER

Figure 15. Elementary Schematic Diagram.

, . - - - - • • PL-2,1FI

~

19


FEDERAL MANUFACTURER'S CODE

From Federal Supply Code for Manufacturers Cataloging Handbooks H4-1

(NMDe to Code) and H4-2 (Code to Name) as supplemented through August, 1968.

Code

01121

01295

07261

07263

07387

07595

07828

07910

079B3

07999

09408

09823

12498

12672

12954

13327

14655

14674

14936

15238

17771

19396

19644

19701

21335

22753

23342

24446

24454

24455

24655

26806

38443

40931

42498

43991

Manufacturer

Jones Mfg. Co, Ch1cago, IllinOIS

Walsco Electronics Corp, L.A .. Calif.

Schweber Electronics, Westburg, L.l., N.Y.

Aerovox Corp, New Bedford, Mass.

Alden Products Co, Brockton, MaliS.

Allen-Bradley, Co, Milwaukee, Wise.

Te)(as Instruments, Inc, Dallas, Texas

FerroxcubeCorp, Saugentes, N.Y. 12477

Fenwal Lab Inc, Monon Grove, Ill.

Amphenol Electron Corp, BroadvteW, Ill.

Fastex, Des Plaines, Ill. 60016

G. E. Sem1con Prod, Syracuse, N Y 13201

Grayburne, Yonkers, N.Y. 10701

Pyroftlm Resistor Co, Cedar Knolls, N.J.

Claire ... Corp, New York, N.Y. 10001

Arrow· Hart & Hegeman, Hartford, Conn.

06106

Motorola, Phoenix, Ar1z, 85008

Engr'd Electronics, Santa Ana, Calif. 92702

Barber-Colman Co, Rockford, Ill. 61101

Wakefteld Eng, Inc, Wakefield, MaS5. 01880

D1g1tron Co, Pasadena, Calif.

Eagle S1gnal ( E.W. Bliss Co), Baraboo, Wtsc.

Avnet Corp, Culver Ctty, Calif, 90230

Fairchild Camera, Mountatn Vtew, Calif.

Btncher Corp, No. Los Angeles, Calif.

Amer Semtcond, Arlington Hts, Ill. 60004

Bodine Corp, Bridgeport, Conn. 06605

BOdtne Electnc Co, Ch1cago, Ill. 60618

Cant Device Corp, Hawthorne, Calif.

State Labs Inc, N.Y., N.Y. 10003

Borg lnst .. Delavan, W1sc. 53115

Vemaltne Prod Co, Franklin Lakes, N.J.

G.E. Semiconductor, Buffalo, N.Y.

Star•Trontcs Inc, Georgetown, Mass. 01830

Burgess Battery Co, Freeport, Ill.

Burndy Corp, Norwalk, Conn, 06852

C.T.S. of Berne, Inc, Berne, Ind. 46711

Chandler Evans Corp, W. Hartford, Conn.

National Semiconductor, Danbury, Conn,

Crystalomcs, Cambridge, Mass. 02140

RCA, Woodbrtdge, N.J.

Clarostat Mfg Co, Jnc, Dover, N.H. 03820

Dtckson Electromcs, Scottsdale, Ariz.

Solltron Devices, Tappan, N.Y. 10983

ITT Semicondlctor-s, W.Palm Beach, Fla.

Corneii·Dubllier Electric Co, Newark, N.J.

Corning Glass Works, Cormng, N.Y.

General Instrument Corp, HICksville, N.Y.

ITT, Semiconductor Div, Lawrence, Mass.

Cutlet-Hammer Inc, Milwaukee, Wtsc, 53233

Spruce Ptne Mica Co, Spruce Ptne, N.C.

Singer Co, Diehl D1v, Somerville, N.J.

Jillnots Tool Works, Pakton Dtv, Chicago, Ill.

LAC ElectrOniCS, Horseheads, N.Y.

Electra Mfg Co, Independence, Kansas 67301

Fafnir Bearjng Co, New Briton, Conn,

UID Electronics Corp, Hollywood, Fla.

Avnet Electronics Corp, Franklin Park, Ill.

G.E., Schenectady, N.Y. 12305

G.E .. Electronics Camp, Syracuse, N.Y.

G. E. !Lamp Div), Nela Park, Cleveland, Ohto

General Red to Co, W. Concord, Mass. 01781

American Zentet Inc, Costa Mesa, Calif.

Hayman Mfg Co, Kemlworth, N.J.

Hoffman Electrontcs Corp, El Monte, Calif.

I.B.M, Armonk, New York

Jensen Mfg. Co, Chicago, Ill. 60638

G. E. Camp, Owensboro, Ky. 42301

Constanta Co, Mont, 19, Que.

P.R. Mallory & Co Inc, Indianapolis, Ind.

Marlln·Rockwetl Corp, Jamestown, N.Y.

Honeywell Inc, MinneapOliS, M,nn, 55408

Muter Co, Chicago, Ill. 60638

National Co, Inc, Melrose, Mass. 02176

Norma-Hoffman, Stanford, Conn. 06904

Code

54715

56289

63743

65083

70485

70563

71294

71400

71744

71785

71823

72619

72699

72765

73138

73445

73559

73899

74193

74861

74970

75042

75382

75915

76005

76149

76487

76545

76684

77166

77263

77042

77630

77638

78189

78277

78488

79963

80030

B0048

80131

80183

Manufacturer

RCA, New York, N.Y.10020

Raytheon Mfg Co, Waltham, Mass. 02154

Sangamo Electric Co, Springfield, Ill. 62705

Shallcross Mfg Co, Selma, N.C.

Shure Brothers, Inc, Evanston, Ill.

Sprague Electric Co, N. Adams, Mass.

Thomas and Betts Co, Elizabeth, N.J. 07207

TRW Inc, !Accessories Div), Cleveland, Oh10

Tornngton Mfg Co, Torrington, Conn.

Union Carbide Corp, New York, N.Y. 10017

Untted-Carr Fastener Corp, Boston, Mass.

Vtctoreen Instrument Co, Inc, Cleveland, 0.

Ward Leonard Electric Co, Mt. Vernon, N.Y.

Westmghouse (Lamp Dtv), Bloomfield, N.J.

Weston Instruments, Newark, N.J.

Atlantic·lndta Rubber, Chicago, Ill. 60607

Ampente Co, Union City, N.J. 07087

Belden Mfg Co, Chtcago, Ill. 60644

Bronson, Homer D, Co, Beacon Fall5, Conn.

Canfteld, H.O. Co, Clifton Forge, va. 24422

Bussman (McGraw Edison), St. Louis, Mo.

ITT Cannon Elec, L.A., Calif. 90031

Centralab, Inc, Milwaukee, Wise, 53212

Continental Carbon Co, Jnc, New York, N.Y.

Cote Coil Co Inc, Prov1dence, R.I.

Chicago Mtntature Lamp Works, Chicago, Ill.

Cinch Mfg Co, Chtcago, Ill. 60624

Darnell Corp, Ltd, Downey, Calif. 90241

Electro Motive Mfg Co, Wilmington, Conn,

Nytrontcs Inc, Berkeley Heights, N.J. 07922

Dialtght Co, Brooklyn, N.Y. 11237

Generallnstr Corp, Newark, N.J. 07104

Drake Mfg Co, Ch1cago, Ill. 60656

Hugh H. Eby Inc, Philadelphia, Penn. 19144

Elastic Stop Nut Corp, Union, N.J. 07083

Ene Technological Products Inc, Erie, Penn,

Beckman Inc, Fullerton, Calif, 92634

Amperex Electronics Co, Hicksvdle, N.Y.

Carltng Electric Co, W.Hartford, Conn.

Elco Reststor Co, New York, N.Y.

JFD Electron,cs Corp, Brooklyn, N.Y.

Heinemann Electnc Co, Trenton, N.J.

Industrial Condenser Corp, Chicago, Ill,

E. F. Johnson Co, Waseca, Minn. 56093 lAC Jnc, Philadelphta, Penn, 19108

Kulka Electric Corp, Mt. Vernon, N.Y.

Lafayette Industrial Electronics, Jam\ca, N.Y. ltnden and Co, Provtdence, R.I.

Litteltuse, Inc, Des Pla1nes, Ill. 60016

Lord Mfg Co, Erie, Penn. 16512

Mallory Electric Corp, Detroit, Mtch, 48204

James Millen Mfg Co, Malden, Mass, 02148

Mueller Electric Co, Cleveland, Ohio 44114

National Tube Co, Pittsburg, Penn,

Oak Mfg Co, Crystal Lake, Ill.

Patton MacGuyer Co, Providence, R.I.

Pass-Seymour, Syracuse, N.Y.

Pierce Robens Rubber Co, Trenton, N.J.

POSitive Lockwasher Co, Newark, N.J.

Ray•Q-Vac Co, Madison, Wtsc.

TRW, Electromc Camp, Camden, N.J. 08103

General Instruments Corp, Brooklyn, N.Y.

Shakeproof (Ill. Tool Works), Elgtn, Ill. 60120

Sigma Instruments Inc, S.Bratntree, Mass,

Stackpole Carbon Co, St. Mary5, Penn.

Ttnnerman Products, Inc, Cleveland, OhiO

RCA, Rec Tube & Semlcond, Harrison, N.J.

Wiremold Co, Hartford, Conn, 06110

Zierick Mfg Co, New Rochelle, N. Y,

Prestole Fastener, Toledo, Oh10

Vtckers Inc, St. Louis, Mo.

ElectroniC Industries Assoc. Washtngton, D.C.

Sprague Products Co, No. Adams, Mass.

Motorola Inc, Franklin Park, IlL 60131

Standard Dtl Co, Lafayette, Ind.

Bourns Inc, R1verside, Calif, 92506

91637

31662

91929

92519

92678

93332

93916

94144

94154

95076

95121

95146

95238

Code

80431

80583

81143

81349

81350

81831

81840

82273

82389

83033

83058

83186

84411

84835

86687

86800

88419

88627

89482

89665

96341

Manufacturer

A1r Fdter Corp, M1lwauku, Wise. 53218

Hammarlund Co, Inc, New York, N.Y.

Beckman Instruments, Inc, Fullenon, Calif. lnternattonat lnsturment, Orange, Conn,

GrayhLII Inc, LaGrange, tit. 60525 lsolantite Mfg Corp, St1rling, N.J. 07980

Military Sp~Kifications

Joint Army· Navy Specifications

Columbus Electronics Corp, Yonkers, N, y.

F11tron Co, Flushing, L.l., N.Y. 11354

Ledex Inc, Dayton, Ohio 45402

Barry-Wrigt1t Corp, Watenown, Mass.

SYivan1a Elec Prod, Emporium, Penn. lndtana Pattern & Model Works, LaPort, Ind.

SWttchcraft Inc, Chicago, Ill. 60630

Metals & Controls Inc, Attleboro, Mass.

Mtlwaukee Reststor Co, Milwaukee, W1sc.

Metssner Mfg, (Maguire lnd) Mt. Carmel, Ill.

Carr Fanener Co, Cambridge, Mass.

Vtctory Engineering, Spnngfield, N.J. 07081

Bearing SPecialty Co, San FranctSCO, CaHf,

Solar Electnc Corp, Warren, Penn.

Un1on Carbtde CorP, New York, N.Y. 10017

Nat1onal Electrontcs Inc, Geneva, Ill.

TAW Capac1tor Dtv, Ogellala, Nebr.

Lehigh Metal Prods, Cambridge, Mass. 02140

TA Mtg Corp, Los Angeles, Calif.

Prectslon Metal Prods, Stoneham, Mass. 02180

RCA \Elect, Camp & Dev), Harrison, N.J.

REC Corp, New Rochelle, N.Y. 10801

Cant Electronics Corp, Brooklyn, N.Y. 11222

Cutler-Hammer Inc, ltncoln, IlL

Gould Nat. Battenes Inc, Trenton, N.J.

Corneii·Dubdler, FuQuay·Varina, N.C.

K & G Mfg Co, New York, N.Y.

HOitzer-Cabot Corp, Boston, Mass.

United Transformer Co, Chicago, Ill.

Mallory Capacitor Co, lndtanapohs, Ind.

Westinghouse E!ectnc Corp, Boston, Mass.

Hardware Products Co, Reading, Penn. 19602

Conttnental Wire Corp, York, Penn. 17405

ITT (Cannon Electric Inc), Salem, Mass.

Johanson Mfg Co, Boonton, N.J. 07005

Au get Inc, Attleboro, Mass. 02703

Chand;er Co, Wethersfield, Conn. 06109

Dale Electromcs Inc, Columbus, Nebr.

Elco Corp, Willow Grove, Penn.

General Instruments, Inc, Dallas, Texas

Honeywell Inc, Freeport, IJJ.

Electra lnsul Corp, Woodstde, l.l., N.Y.

E.G.&G., Boston, Mass.

~~~~~~ap~~~c~c:ocd~: ~nee~ ~~~~~~-~~;s0 013

Raytheon Co, Components Dtv, Quincy, Mass.

Tung Sol Electric Inc, Newark, N.J.

Garde Mfg Co, Cumberland, R.I.

Quality Components Inc, St. Mary's, Penn.

Alec Electronics Mfg Co, Lawrence, Mass.

Continental Connector Corp, Woodside, N.Y.

V+tramon, Inc, Bridgeport, Conn,

Methode Mfg Co, Ch1cago, Ill.

General Electric Co, Schenectady, N.Y.

Anaconda A mer 8ra55 Co, Torrtngton, Conn.

H1-Q D1v, at Aerovox CorP, Orlean, N.Y.

Texas Instruments Inc, Dallas, Texas 75209

Thordarson-Meiuner, Mt. Carmel, ill,

Microwave As5octates Inc, Burltngton, Mass.

Amphenol Corp, Jonesville, Wise, 53545

Military Standards

Seaiectro Corp, Mamaroneck, N.Y. 10544

Compar Inc, Burltngame, Caltf,

North Hills ElectroniCS tnc, Glen Cove, N.Y.

Transttron Electromcs Corp, Melrose, Mass.

Varian, Palo Alto, Calif. 94303

Atlee Corp, Winchester, Mass. 01890

Delevan EJectromcs Corp, E. Aurora, N.Y.

9/68


et7 :ae•-••oo

GENERAL RADIO

et7 •••-7•oo

. t

. I

- J

;

DISTRICT OFFICES

I

METROPOLITAN

NEW YORK*

'~

\

'

·

CHICAGO*

9440 W . Fosler A ...

845 IJooad AY en u e

R i dg e fi e ld, New Ieney 076S7

Tele p hone N .

r . 2J2 964-2722

Ch i cago, Ill i nois 60656 lJ 2 992 0800

N.J

. 20J 94l lJ 4 0

CLEVELAND

SYRACUSE

P ic lra r d iJ u i ld i ng foal Molloy Rood

S7racuse . New Y o r l J 3 2 fl

Jeleplton e 31.5 4.54

9323

5579 ,._,I Rood

Cfe Y eland, Ohia 4 4 J 29

T el ephen e 2J6 886 0JSO

NEW ENGLAND*

22 lalrer AY en ue

Werf Concord, ltl a uochurellr OJ71JJ

Telephon e 6r 7 646 0550

LOS ANGELES*

JOOO North S e wa r d Sl rH I los Angel e s, California 90038

2J3

FRANCISCO

626 San Anton i o Rood

PHILADELPHIA

Fo r t Waslt i nglon lndurrriol Par ..

Fori Waslt i n.,on , P e nnsyiYania l9034

T e l.,hane 2 J'I 646-8030

WASHifiGTON*

AND BALTIMORE

RoclcYille Pilce flochille , Maryland 208.52

T el e phone 30J 946 J600

ORLANDO

J J 3 fasl Coloni a l OriYe

Orlando, Florida 32801

Telephene 305 425 4671

DALLAS*

2600 Slemmonr Fre e way, Su ite 2JO •

Dallas, T u as 75207

Telepltone 2J4 637 2240

TORONTO*

99 flnool Porlway

To ro nto J .5

, Onta r i o, Canada

Telepltone 4J6 247 2J7l

• Rept~lr s ervic e s are GYailabl e al thes e dist rl cl a lll cn .

I 255 lai r d IJoul e Yard

Town of Mount Re,.al

, Quebec, Canada

Telephone 5J 4 7373 673

OTTAW A T e l ephon e

6U ~ 33-4237

General Radio Company (Overseas} , 8008 Zurich , Switzerland

G e neral Radio Company (U.K.J Limited, Bourne End, Buckinghamshire, E11gland

Repres e ntatives in Principal Overseas Countries

Prin ~ ;,. U SA

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1551-C Sound Lever Mtr., Manual

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INSTRUCTION MANUAL

Type 1551-C

Sound-Level

Meter

GENERAL RADIO

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CONTENTS

Type 1551-C

Sound- Leve I

Meter

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SPECIFICATIONS

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SPECIFICATIONS (Con't)

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TABLE OF CONTENTS

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Section 1

INTRODUCTION

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Section

OPERATING PROCEDURE

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Section 3

CALIBRATION

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Section

SERVICE AND MAINTENANCE

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TABLE OF VOLTAGES AND RESISTANCES.

*

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