Model 1400 and 2400 Instructions

I. INTRODUCTION TO THE MODEL 1400/2400 The Quest models 1400 and 2400 Sound Level Meters measure frequency weighted and time averaged sound pressure level. Applications include laboratory, industrial, community, military and audiometric measurement or analysis.

A yellow UNDERRANGE LED will light if the meter is in the high range setting to indicate that signal levels are too low to provide an accurate reading. This indicator signals the user to switch to the low range setting to prevent erroneous readings and occurs at approximately 64dB.

The models 1400 and 2400 are hand held meters with an LCD display that provides a numerical readout. They are housed in a tough die-cast metal case. The meter is operated with easy-to-use slide switches. Two output jacks are provided for connecting to peripheral devices such as chart recorders, oscilloscopes, audio recorders, etc. The model 1400 provides Type 1 accuracy for critical measurements. The model 2400 provides Type 2 accuracy for general field survey work. As both meters are operationally identical, this manual will refer only to the model 1400 except where appropriate. II. ABOUT THE METER (Refer to Figure 1.) A. The Display The LCD display provides a numeric readout of sound level in 0.1dB increments along with a LOBAT (low battery) indicator. In the RUN mode the numeric display provides a reading of the maximum sound pressure level measured during the previous second. In the HOLD mode the display holds the highest reading encountered since the meter was placed in HOLD, or since the last time RESET was pressed. The LOBAT indicator will light when the voltage of either battery is too low to allow an accurate reading. A red OVERRANGE LED will light when signal peaks cause an overload condition in the electronics. This indicator signals the user to switch to the high range setting to prevent erroneous readings. Figure 1 1400 Sound Level Meter 3

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B. Meter Controls

WEIGHTING Switch

RUN/HOLD/RESET Switch With the switch set to RUN the meter continuously displays sound level, automatically updating the current reading at a rate of once per second. Setting the switch to HOLD causes the display to hold the highest SPL encountered thus far. As a higher SPL occurs the display changes to show the new value. To reset the value stored within the model 1400, slide the switch from HOLD to RESET, hold for a few seconds, and release. The switch will automatically return to the HOLD position. This will erase the previous MAX value (and display the current value) prior to taking new readings. For response times see Figures 10 and 11. FAST/SLOW RESPONSE Switch

The WEIGHTING switch controls the frequency response of the meter, Weightings A or C may be selected. (See section V, part C, Weighting Characteristics, for further information.) dB RANGE Switch The displayed range of the model 1400 is 70 dB and is switchable between LOW (30-100 dB) and HIGH (70-140 dB). After switching ranges allow several seconds for the meter electronics to stabilize. POWER Switch This switch turns the power to the meter ON and OFF.

The RESPONSE switch controls the rate at which the meter responds to changing input signals. Most sound measurements are done with the response set to SLOW. The FAST response is generally used when measuring short duration noises such as moving vehicles. The RESPONSE switch positions are as follows: FAST - 125 millisecond time constant. (See Figure 10.) SLOW - 1 second time constant. (See Figure 11.)

C. Overload Detection and Underrange Indicator The overload indicator is displayed whenever the incoming signal saturates (overloads) the circuitry. It is a red LED to the right of the display. If the overload indicator is on while taking measurements in the LOW range, increasing the dB RANGE switch should cause the overload to disappear. If you are already on the HIGH range setting and an overload condition still exists, the sound level that you are measuring is beyond the capability of the 1400 due to either an extremely high rms value or a high crest factor (peak to rms ratio). The underrange indicator is a yellow LED to the right of the display. When the meter is in the HIGH range and the signal is below the noise floor of the meter, this indicator will light. You should switch to the LOW range to prevent misinterpreting the displayed value as being accurate. This will occur at approximately 64dB. D. Output Jacks The model 1400 provides output jacks for measuring the weighted AC signal before the rms/log detector and the DC output of that detector. These jacks may be connected to any load without affecting the operation of the meter. Connection to low impedance loads will require correction for the 1 Kohm impedance of these outputs and will also decrease battery life. All output jacks use a 3.5mm stereo plug. (See Figure 2, Output Jack Connections.) The following describes each output function: DC - The Sound Pressure Level (SPL) over Figure 2 Output Jack Connections

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the range selected is linearly represented by a DC output. Zero volts is equal to 100dB regardless of the range setting. The output changes 16.7mV/dB or 1V/60dB. This output is primarily provided for connecting a 0 to 1 volt span chart recorder. (See section IV. D., Chart Recording and Figure 5, Chart Recording of SPL) AC - This jack provides the amplified, weighted AC signal from the input of the RMS detector. An output level of 100dB corresponds to a voltage of 0.85 volts RMS on the LOW range and 8.5 millivolts RMS on the HIGH range setting.

IV. GENERAL OPERATING CONSIDERATIONS Before taking measurements with the model 1400, there is a series checks and considerations that should be performed or noted.

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After switching the unit ON, check for a LOBAT indication on the display, showing that the batteries are weak and need replacing. Although the model 1400 will maintain accurate calibration over a long period of time, the calibration should be checked and the meter slightly adjusted, if necessary, before each use. The calibration should also be checked after each use.

III. CHECKING THE METER INTEGRITY A. Battery Check At any time, if the LOBAT indicator on the display is activated it is recommended that the user replace both 9 volt batteries. Alkaline batteries are recommended for best performance. Refer to the meter bottom for battery replacement.

Set the RESPONSE, WEIGHTING, MODE, and dB RANGE switches as needed. Hold, set, or tripod mount the meter in the desired location. If a MAX measurement is needed, be sure to reset the meter before taking the measurements. It is always a good idea to document all measurement conditions settings for possible future reference.

and meter

B. Calibration A. Meter / Microphone Placement The model 1400 may be calibrated in either the LOW or HIGH range. To check the calibration of the model 1400, perform the following procedure using a Quest Calibrator. There is no warm up period required, but for maximum accuracy calibration of the model 1400 should be performed at the temperature of the environment to be measured.

Whenever possible, the meter should be tripod-mounted in a relatively open area to minimize reflections from the body or other large reflective structures. Avoid placement against a wall or in a corner. A threaded bushing on the back will accept a standard 1/4-20 tripod fitting. The .50 inch diameter microphone cartridges used on the models 1400 and 2400 are free-field microphones. Point the meter directly at the noise source ( 0 degrees ).

1. 2.

Perform a battery check (LOBAT indicator is not on). Turn the calibrator ON. If optional, set the frequency to Note the SPL output of the calibrator.

3.

Place the black adapter ring fully onto the microphone.

B. Background Noise

4.

Place the calibrator onto the adapter.

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Set the model 1400 to RUN, SLOW or FAST, HIGH or LOW range (as appropriate for your calibrator).

Background noise can cause considerable error in measurement when its intensity is close to that of a particular sound source of interest. When it is not possible to eliminate or reduce the background noise, use the curve shown in Figure 3 to correct for the effect of the background noise on the measurement.

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Use a small screwdriver to adjust the calibration control, located through the small hole on the front of the meter, until the display indicates the correct SPL, taking into account any corrections for temperature or altitude. Refer to your calibrator manual.

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1KHz.

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D. Chart Recording The model 1400 has a DC output that is linearly related to the deciBel reading on the LCD display by 16.7mV/dB (1V/60db). Nominal output voltages for a range of readings are as follows:

Figure 3 Effects of Background Noise C. Wind Screen Effects To prevent measurement errors caused by wind blowing across the microphone, the use of a windscreen is recommended. The wind screen will reduce wind effects and will also help protect the microphone under dusty or oily conditions. Acoustic attenuation effects of the WS-7 windscreen are shown in Figure 4.

Figure 4 Effects of WS-7

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SOUND PRESSURE READING

LOW RANGE DC VOLTAGE

HIGH RANGE DC VOLTAGE

30dB

-1.167VDC

----

40dB

-1.000VDC

----

50dB

- .833VDC

----

60dB

- .666VDC

----

70dB

- .500VDC

- .500VDC

80dB

- .333VDC

- .333VDC

90dB

- .166VDC

- .166VDC

100dB

OVDC

+/-15mV

0VDC

+/-15mV

110dB

----

.167VDC

120dB

----

.333VDC

130dB

----

.500VDC

140dB

----

.666VDC

This output, capable of driving up to 100 feet of shielded or twisted pair cable, is intended for use with a 0 to 1 volt DC input chart recorder or data acquisition device that has a high input impedance. The output impedance is 1000 ohms. Chart recorder input impedance may cause loading of this output, which should be taken into account. Multiplication factors for the above numbers are given below for various chart recorder input impedances. INPUT IMPEDANCE OF RECORDER

MULTIPLY DC VOLTAGE BY:

10 KOHM

0.909

20 KOHM

0.952

50 KOHM

0.980

100 KOHM

0.990

Connect the model 1400 to the chart recorder input with proper polarity such that the pen is on the proper side of the chartpaper with respect to time and that the pen moves in the proper direction with increasing deciBel level. A zero reading 10

corresponding to 100dB may be obtained by sorting together the inputs to the chart recorder (some recorders have a momentary 'ZERO' button) and using the 'zero pen position' control on the recorder to position 100dB at a desired level on the recorder. All measurements on the recorder will be relative to this 100dB reference. If you are measuring on the LOW range you will want to set 100dB at or near the top of the chart. If you are measuring on the HIGH range you will want to set 100dB in the bottom half of the chart, keeping in mind that this range is not usable much below 70dB. Note that this 100dB value has a +/-1dB tolerance.

V. TECHNICAL INFORMATION A. Principles of Operation The Quest model 1400 uses low noise, low power analog and digital integrated circuitry to ensure long battery life, maximum stability, and superior reliability over a wide range of environmental conditions. Figure 6 is a block diagram of the model 1400's internal circuit operations.

A more accurate method would be to use an acoustic calibrator to calibrate the chart recorder as follows: 1. Turn the meter to ON. Place the adapter onto the microphone. 2.

Place the calibrator onto the adapter.

3. Turn the calibrator ON to produce 114dB (or other level) at 1 kHz. Use the zero adjust control on your chart recorder to set the pen to the desired level corresponding to 114dB (or other level) on your chart recorder. Refer to Figure 5, Chart Recording of SPL. 4. Be sure to document all chart recorder settings and meter settings when taking measurements. The Quest model 411 chart recorder is recommended for time-history recording using the model 1400. The use of QUEST CHART PAPER 58-653, which has 12 major divisions corresponding to 5dB/division or 60dB full scale, will simplify the recorder setup and reading.

Figure 6 1400 Block Diagram

B. Microphone The model 1400 is designed to accept a prepolarized (electret) microphone Model QE4846 exclusively. The impedance of this microphone is 18pF. The microphone screws directly onto the microphone extension which is part of the meter case.

Figure 5 Chart Recording

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C. Weighting Characteristics

The model 2400 is designed to accept a prepolarized (electret) microphone Model QE7052 exclusively. The impedance of this microphone is 15pF. The microphone screws directly onto the microphone extension which is part of the meter case.

The weighting characteristics (frequency response) for A and C are shown in Figure 8. The "A" weighting response emulates the low level response of the human ear and is used for most industrial and community noise measurements. Generally, "C" weighting is used for measuring noise reduction in hearing protectors and for other scientific purposes.

A typical response curve for the microphones is shown in Figure 7.

Figure 8. A & C Weighting Figure 7 QE4846 or QE7052 Microphone Response CAUTION : When installing or removing the microphone, do not unscrew the protective grid. Do not touch the microphone diaphragm under this grid as permanent damage may result.

D. Internal Electrical Noise The normal measurement range of the 1400 Meter is approximately 30 to 140 dBA and 40 to 140 dBC. The inherent noise level is typically 23 dBA. 13

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E. Tone Burst Response

VI. SPECIFICATIONS Standards: Model 1400 : Type 1 ; Model 2400 : Type 2 ANSI S1.4-1983, IEC 651-1979 Display: 3 1/2 Digit Liquid Crystal Display. Level display indicates to 0.1 dB resolution. Annunciator is included for Battery Check. LED indicators are used for overrange and underrange conditions. Modes of Operation: Measures sound pressure level (SPL) or maximum level (MAX). Range :

30 to 140 dBA 40 to 140 dBC

Electrical Noise Floor : 23dBA, 30dBC typical AC Gain Calibration: External calibration adjustment available on front of meter near the microphone. Calibrate using a 1000Hz acoustic calibrator that is properly adapted to the microphone.

Figure 9 Fast Response

Frequency Weighting Networks: A, and C. Meter Response: Slow and Fast. Microphone: Removable .52 inch diameter prepolarized condenser (electret) microphone Model 1400 : QE4146 - Type 1 accuracy Model 2400 : QE7052 - Type 2 accuracy AC Output: 0.85V RMS at 100 dB on LOW range. 8.5mV RMS at 100 dB on HIGH range. 1000 ohm output impedance, 1/8 inch phone jack DC Output: 0VDC +/- 15mV at 100 dB. Each 0.167V change equals 10dB (1V/60dB). 1000 ohm output impedance, 1/8 inch phone jack Detector: True RMS. For crest factor capability see figure 12. Accuracy: Within 0.5 dB at 25°C; Within 1.0 dB over the temperature range of -10°C to +50°C

Figure 10 Slow Response Figures 9 and 10 show the meter response to a sinewave input of various pulse durations for Fast and Slow settings.

Attenuator Accuracy: Within 0.5dB from 20-8000 Hz within 1.0 dB from 20-12,500 Hz. Overload Indication: A red LED indicates overload.

The nominal decay time is 34.7 dB per second for FAST and 4.35 dB per second for SLOW.

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Underrange Indicator: A yellow LED indicates signal below range. Crest Factor: Greater than 26dB (crest factor = 20) if peak of 16

Temperature Range: Operation: -10NC to +50NC Storage (less batteries): -20NC to +60NC Operating Humidity: 0 to 95% relative humidity, non-condensing. Batteries: Two 9-volt alkaline batteries (NEDA 1604A) will provide approximately 25 hours of continuous operation. Effect of Electromagnetic Fields: A magnetic field of 1 Oersted (80A/m) at 60Hz produces a maximum reading of 40 dB on C weighting. Less than 1dB error when exposed to RF fields up to 10V/m over a frequency range of 10MHz to 500MHz. Less than 1dB error for readings of 80dB or greater when exposed to RF fields up to 25V/m over a frequency range of 10MHz to 500MHz. Effect of Electrostatic Fields: Negligible. Tripod Mount: A threaded insert on back of the meter accepts a standard 1/4-20 tripod mounting screw. Size : 2.75 x 7.6 x 1.0 inches (70 x 193 x 25mm) not including the height of the microphone housing. The microphone extends 1.5 inches (38mm). Weight: 15 oz. (425g) including batteries. VII. Figure 11 Maximum Crest Factor Capability signal does not cause an overload. Crest factor is sufficient to handle the signal if the overload indicator does not light.

ACCESSORIES 58-928 Calibrator Adapter for 0.52 inch diameter microphone for use with Quest "CA-" series calibrators 56-990 Calibrator Adapter for 0.52 inch diameter microphone for use with Quest "QC-" series calibrators 59-344

WS-7 Windscreen for 0.52 inch microphone (pkg. of 3)

59-045

Tripod (Larger)

59-046

Tripod (Smaller)

58-948 Recorder Input Cable - 1/8 inch phone plug to double banana plug 59-703

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Input Adapter - Female BNC jack to 1/2" microphone thread

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VIII.

SERVICE AND WARRANTY POLICY

Service Policy The Quest product you have purchased is one of the finest acoustic instruments available. It is backed by our full one year warranty which seeks complete customer satisfaction. This is your assurance that you can expect prompt courteous service for your equipment from the entire Quest service organization. Should your Quest equipment need to be returned for repair or recalibration, please contact the Service Department at 1(800)245-0779 (USA) or Fax (262)567-4047 for a Return Authorization Number. The RA number is valid for 30 days, and must be shown on the shipping label and purchase order/cover letter. If you are unable to return instruments in that time call for a new RA number. Send it prepaid and properly packed in the original shipping carton directly to Quest Technologies, 1060 Corporate Center Dr., Oconomowoc, WI 53066 U.S.A. Repair or replacement work done under warranty will be performed free of charge, and the instrument will be returned to you prepaid. Your copy or a photocopy of the Quest Registration Card will serve as proof of warranty should the factory require this information. If for any reason you should find it necessary to contact the factory regarding service or shipping damage, please direct your calls or letters to the attention of the Service Manager, Quest Technologies, (262) 567-9157 or (800) 245-0779. Office hours are from 8 AM to 5 PM (Central Standard Time) Monday through Friday. Warranty: Quest Technologies warrants our instruments to be free from defects in materials and workmanship for one year under normal conditions of use and service. For U.S.A. customers we will replace or repair (our option) defective instruments at no charge, excluding batteries, abuse, misuse, alterations, physical damage, or instruments previously repaired by other than Quest Technologies. Microphones, sensors, printers and chart recorders may have shorter warranty periods. This warranty states our total obligation in place of any other warranties expressed or implied. Our warranty does not include any liability or obligation directly resulting from any defective instrument or product or any associated damages, injuries, or property loss, including loss of use or measurement data. For warranty outside the U.S.A., a minimum of one year warranty applies to the same limitation and exceptions as above with service provided or arranged through the authorized Quest sales agent or our Quest European Service Laboratory. Foreign purchasers should contact the local Quest sales agent for details.

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