Monarch Instrument 321 Operating Manual

MONARCH INSTRUMENT

Instruction Manual

© Monarch Instrument 2002 all rights reserved

1071-8051-110

Monarch 321

Sound Level Meter

15 Columbia Drive
Amherst, NH 03031-2334 USA
Phone: [phone]
Fax: [phone]
E-mail: [e-mail]
Website: www.monarchinstrument.com

Safeguards and Precautions

1. Read and follow all instructions in this manual
carefully, and retain this manual for future reference.

2. Do not use this instrument in any manner inconsistent
with these operating instructions or under any
conditions that exceed the environmental
specifications stated.

3. When making measurements in high noise
environments, be sure to use proper hearing
protection.

4. This instrument is not user serviceable. For technical
assistance, contact the sales organization from which
you purchased the product or Monarch
Instrument directly.

LIMITED WARRANTY

SELLER warrants hardware products to be free from any defect in materials or workmanship
for a period of one (1) year from date of shipment to BUYER. SELLER’s entire liability and
BUYER’s sole and exclusive remedy resulting from any defect in workmanship or material
in the hardware product covered by this limited warranty shall be limited to and fully
discharged by the SELLER’s option of replacement or repair of such item without charge.
The limited warranty provided in this clause is in lieu of all other warranties, expressed or
implied, arising by law or otherwise. ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE ARE EXCLUDED. This limited warranty
shall not be modified except by an arrangement signed by both parties specifically
referencing this clause.

SELLER warrants that any software supplied will operate in accordance with the
documentation or manual supplied therewith in all material respects when used in strict
compliance with such documentation or manual. Notwithstanding the foregoing, BUYER
acknowledges that, since software is complex and therefore may have defects, BUYER’s
sole and exclusive remedy for any such defects or breach of this warranty shall be to
require SELLER, within a reasonable period of time, to provide all reasonable programming
services to correct programming errors in the software. Except as provided above SELLER
MAKES AND BUYER RECEIVES FROM SELLER NO EXPRESS OR IMPLIED WARRANTIES
OF ANY KIND WITH RESPECT TO ALL OR ANY PORTION OF SOFTWARE AND BUYER
HEREBY AGREES AND ACKNOWLEDGES THAT IT ACCEPTS THE SOFTWARE IN ‘AS IS’
CONDITION. SELLER HEREBY EXPRESSLY EXCLUDES ANY IMPLIED WARRANTIES
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO
THE SOFTWARE. BUYER agrees that any specific right or remedy granted to BUYER
hereunder with respect to any breach or default by SELLER shall be in lieu of all other
rights and remedies otherwise available to BUYER at law or in equity as the result of such
breach or default, regardless of whether based on contract, tort, strict liability, or other
theory of liability.

IN NO EVENT SHALL SELLER BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, OR PUNITIVE LOSSES OR DAMAGES (INCLUDING, BUT NOT
LIMITED TO, LOSSES OR DAMAGES FOR ANY LOST PROFITS OR LOST DATA) AS THE
RESULT OF ANY BREACH OR DEFAULT BY SELLER WITH RESPECT TO THE HARDWARE
OR SOFTWARE, EVEN IF SELLER HAS BEEN ADVISED OR MADE AWARE OF THE
POSSIBILITY OF ANY SUCH LOSSES OR DAMAGES AND REGARDLESS OF WHETHER
THE CLAIM IS BASED ON CONTRACT, TORT, STRICT LIABILITY, OR OTHER THEORY OF
LIABILITY.

This limited warranty does not extend or apply to consumables (including, but not limited
to, lamps and batteries, if applicable) or equipment, instruments or accessories which are
warranted separately by the original manufacturer of these items.

DECLARATION OF CONFORMITY

Monarch Instrument

Division of Monarch International Inc.

15 Columbia Drive, Amherst NH 03031 USA

declares that the product:

Name: Sound Level Meter
Model: Monarch 321

to which this declaration relates is in conformity with the following standards:

EMC: EN55011/1991 Class B

EN50082-1/1997 / EN61000-4

and therefore conforms in accordance with 89/336/EEC-EMC Directive. The
testing of this product was performed by GesTek EMC Lab. in March of

2001. (Ref. No. 0102072E).

MODEL 321 SOUND LEVEL METER

Table of Contents

Section Page

1.0 Introduction

.................................................................................................................

2.0 Specifications

............................................................................................................

3.0 Symbol Definitions and Feature Locations

4.0 Control Functions

4.1 Power and Backlight....................................................................................................3

4.2 Frequency Weighting Selection .................................................................................

4.3 Time Weighting Selection ...........................................................................................

4.4 Level Selection.............................................................................................................

4.5 MAX / MIN Function .....................................................................................................

4.6 Auto Power Off.............................................................................................................

4.7 Low Battery Condition.................................................................................................

4.8 Digital Output ...............................................................................................................

4.9 AC and DC Output Signals..........................................................................................

...................................................................................................

5.0 Calibration Procedure

5.1 Calibration Requirements ...........................................................................................4

5.2 Calibration Settings .....................................................................................................

5.3 Installing Acoustic Calibrator .....................................................................................

5.4 Adjusting Calibration...................................................................................................

5.5 Re-calibration ...............................................................................................................

.........................................................................................

6.0 Operating Instructions

6.1 Preparation for Measurement .....................................................................................5

6.2 Instrument Placement .................................................................................................

6.3 Taking Readings ..........................................................................................................

6.4 Preparation for Storage...............................................................................................

........................................................................................

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14th March 2000

Importer (Amherst, NH) Alan Woolfson, VP Engineering (Authorized Signature)

MODEL 321 SOUND LEVEL METER

1.0 Introduction:

This instrument is a Type 2 Sound Level Meter intended for general-purpose measurements
of sound pressure levels in industrial and environmental applications. It is equipped with A
and C frequency weighting and Fast and Slow time weighting. It complies with IEC651 Type
2 and ANSI S1.4 Type 2 standards. It is provided with both an ac output of 0-1 Vrms over the
full scale of the range selected and a dc output of 10 mV/dB, plus a RS232 interface for bi­directional communication with a PC.

2.0 Specifications:

Standard Compliance: IEC651 Type 2, ANSI S1.4 Type 2
Measurement range: 30 - 130dB
Dynamic range: 50 dB
Scale Ranges: Low: 30 - 80dB

Medium: 50 - 100 dB
High: 80 - 130 dB
Auto: 30 - 130 dB

Frequency range: 31.5Hz - 8KHz
Frequency weighting: A, C
Time weighting: Fast (125 mS), Slow (1 sec.)
Microphone: 1/2 inch electret condenser microphone
Digital display: 4 digits
Resolution: 0.1dB
Update Rate: 0.5 sec.
Analog display: 50 segment bargraph
Resolution: 1dB
Update Rate: 50mS
Accuracy: ±1.5dB (under reference conditions, 94dB @ 1KHz)
Out of Range Indication: Displays ‘OVER’ when overrange for bargraph scale selected

Displays ‘UNDER’ when underrange for bargraph scale selected
Displays ‘-LO.-‘ when underrange is by least 20 dB

MAX/MIN hold: Maximum and Minimum RMS value hold
Digital output: Bi-directional RS232
AC output: 0 – 1 Vrms over scale range selected

Approx.100ȍ output impedance
DC output: 10 mV/dB

Approx.1Kȍ output impedance

Power requirement: 9 Volt battery, NEDA 1604 or JIS 006P or IEC 6F22
Battery life: Approx. 50 hours with alkaline battery. Low battery indication.

Operating Conditions:

x Operating Temperature and Humidity: 0°C - 40°C (32°F - 104°F); 10 - 90% RH

x Storage Temperature and Humidity: -10°C - 60°C (14°F - 140°F); 10 - 75% RH

x Altitude up to 2000 meters (6500 feet)

Dimensions: 275×64×30mm (10.8×2.5×1.2 in)
Weight: Approx.285g (10.0 oz)

Accessories: Windscreen, Battery, Carrying Case, 3.5 mm Plug, Screwdriver, Instruction

Manual

Options: AC Adaptor: 9VDC (8-15VDC Max.) @ 30mA, 3.5mm (+), 1.35mm (-)
Software and RS232 cable

Non-condensing

Non-condensing

Notes

1

A

MODEL 321 SOUND LEVEL METER

6.0 Operating Instructions:

6.1 Preparation for Measurements

Determine if the instrument is properly calibrated or requires calibration in accordance
with Section 5.0.
When being operated in an environment with a wind or airflow in excess of 10 m/sec.,
install a windscreen over the microphone to minimize wind interference. It is actually
good operating practice to leave the windscreen on the instrument at all times of
measurement to avoid extraneous interference from unknown air motion.
Note: The windscreen will not protect the microphone from moisture or contamination.
Take appropriate precautions to avoid prolonged use in dirty environments, wetness or
severe vibration.
Turn the instrument on and adjust the frequency weighting, time weighting and scale
level in accordance with the provisions of Sections 4.2, 4.3 and 4.4 respectively. Disable
MAX / MIN (Section 4.5) until proper operating conditions have been established.

6.2 Instrument Placement

Proper placement of the instrument is critical to accurate measurements.
Worker exposure: Applicable standards require that the sound level meter be located
within two feet (if achievable) of the ear of a worker being tested for noise exposure and
aimed in the general direction of the noise source. In the event of differing noise level
exposure at each ear, measurements should be taken for the ear experiencing the
highest incident noise.
Area Surveys: Locating the sound level meter will be governed by the purpose of an
area survey. If the purpose is determining noise nuisance at an adjacent boundary, the
instrument should be mounted on a tripod at the boundary and facing the noise source.
Other situations may determine other placement criteria to accomplish the desired
measurement objective.

6.3 Taking Readings

Both the digital display and the analog bargraph will display current sound level readings
in the normal operating mode.
When the sound level drops from an interim high, the bargraph will maintain a bar at the
highest level reached for a brief moment after the level drops.
When in the MAX /MIN mode, the digital display will indicate the MAX or MIN as
selected, but the analog bargraph will still respond to actual changing noise conditions.

6.4 Preparation for Storage

When measurements are completed and the instrument is to be stored, turn it off and
remove the battery when not in use. Always store the instrument in a cool and dry
environment.

MODEL 321 SOUND LEVEL METER

3.0 Symbol Definitions and Feature Locations:

UNDER : Value is underrange for bargraph scale selected

MAX

MIN

FAST

SLOW

: The Maximum value is now being displayed

: The Minimum value is now being displayed

: Fast time weighting mode (125mS)

: Slow time weighting mode (1 Sec.)

OVER : Value is overrange for bargraph scale selected

: Analog (bargraph) scale range

AUTO : Indicates ‘Auto Level Range’ selected

: Indicates ‘Auto Power Off’ is enabled

dBA : A frequency weighting mode

: Low battery indication. Battery voltage is not sufficient for proper operation.

-LO.-

dBC

: Indicates value is underrange by at least 20 dB

: C frequency weighting mode

1

8

Feature Locations:

1) Windscreen 8) ½ inch electret microphone

2) LCD display 9) Offset calibration screw

3) ON/OFF button 10) Digital output connector (RS232)

4) MAX MIN button 11) AC and DC output signals connector

5) Scale Range Up and Down 12) AC Power Adaptor connector

6) Frequency weighting button 13) Tripod connector

7) Time weighting button 14) Battery compartment cover

2

3
4
5

C

MA

FAS
SLO

MI

LEVEL

3

80

Lo

5

100

Med
Hi

130 38

Aut

130

IEC 651 TY PE

POWER-UP

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7

C

R
S-

O
UT

P
D
C

13

9

10

11

12

14

9V

NEDA 1604

PLEASE

MANUAL FOR

OPEN

5

2

MODEL 321 SOUND LEVEL METER

A

4.0 Control Functions:

4.1 Power and Backlight

The button turns both the instrument power and the display backlight ON or OFF.
Press it once to turn the power ON. Every subsequent momentary press toggles the
backlight ON or OFF. Press and hold this button for 3 seconds to turn the power OFF.

4.2 Frequency Weighting Selection

The frequency weighting selected is determined by the measurement application.
A Weighting: Used for safety compliance and worker exposure applications, as the A
weighting most accurately emulates the frequency response of the human ear.
C Weighting: Used for environments containing a significant low frequency noise
content, as the C weighting represents a more uniform response over a wider frequency
range including low frequencies.
A significant difference between A weighted and C weighted results in the same
environment is indicative of a substantial low frequency noise content.

4.3 Time Weighting Selection

The time weighting selected is determined by the noise content and how rapidly it varies.
Fast: 125 mS averaging time. The Fast time averaging mode is most commonly used to
observe the range of sound level variation in the measured environment. Because of the
relatively short averaging time, Fast response mode more accurately displays maximum
and minimum sound levels experienced. When there is less than 6 dB difference
between the maximum and minimum levels, the average sound level may generally be
considered to be half way between the two. When there is a greater than 6 dB variation
in levels, the average is considered to be 3 dB below the maximum.
Slow: 1 Second averaging time. The Slow time averaging mode is commonly used for
observing the average level over a long term. The slow response mode is required in the
IEC and ANSI standards for long-term worker exposure determinations.

4.4 Level Selection

The sound level range to be displayed is determined by the average sound level
experienced and the extremes of level variation about that average. Selection of Low
(30 – 80 dB), Medium (50 – 100 dB), High (80 – 130 dB) or Auto (30 – 130 dB) is
determined by the Up and Down arrow buttons, which sequentially move through the
range selections in either direction. Note that if the average sound level is outside the
range selected in either direction, this will be indicated by the appearance of UNDER or

OVER on the display. In the event that the level is more than 20 dB below the lower end

of the range selected, the display will indicate

4.5 MAX / MIN Function

Once the appropriate weighting and level selections have been made, both the
Maximum and Minimum levels may be captured and sequentially displayed. Pressing the
MAX MIN button will first display the MAX symbol and value for the current
measurement series. Pressing the MAX MIN button again moves the display to the MIN
symbol and value. The next press of this button causes both the MAX and MIN symbols
to flash and the displayed value returns to the current reading. Each successive press of
the MAX MIN button circulates the display mode among these options.
To exit the MAX / MIN mode, press and hold the MAX MIN button for two seconds.

4.6 Auto Power Off

By default, the instrument powers on in the ‘Auto Power Off’ mode and will automatically
shut off 30 minutes after the last key operation or RS232 communication.
To disable this feature, press and hold the FAST SLOW button and then power on the
meter. The will not be displayed, indicating that ‘Auto Power Off’ is disabled.

4.7 Low Battery Condition

When the battery voltage is at or below the minimum for proper operation, the
symbol will show on the display indicating that the battery must be replaced.

4.8 Digital Output

The RS232 Digital Output is a 9600 bps N 81 serial interface.
RX is a 5V normally high input port.
TX is a 5V normally high output port.

-LO.-

.

MODEL 321 SOUND LEVEL METER

4.9 AC and DC Output Signals

The AC and DC output signals are combined on individual rings of the output connector
as shown below.
AC: The AC output is 0 – 1 Vrms over the full scale of the

AC Signal

DC Signal

Ground

range selected. The output impedance of this signal is
approximately 100ȍ. It is supplied to the tip of the 3.5mm
coaxial connector.
Note: In the AUTO level range, the AC signal will default to the appropriate LOW,
MEDIUM or HIGH scale limits.
DC: The DC output is 10mV/db with an output impedance of 1K ȍ. It is supplied to the
middle ring of the 3.5mm coaxial connector.

5.0 Calibration Procedure:

5.1 Calibration requirements

Calibration of the sound level meter should be conducted prior to and immediately after
any critical measurements or following any prolonged storage of the instrument.
Calibration requires the use of an optional Acoustic Calibrator providing a 94 dB, 1 KHz
sine wave signal.

5.2 Calibration Settings

Turn the instrument on and select the following settings:

Frequency weighting: A
Time weighting: Fast
Level range: 50 – 100 dB
MAX / MIN Mode: Disabled

5.3 Installing Acoustic Calibrator

Insert the microphone housing carefully into the
opening of the acoustic calibrator. Be sure the
calibrator is seated firmly against the top of the
microphone, but do not apply excessive force which
could damage the microphone.

5.4 Adjusting Calibration

Turn the acoustic calibrator on and observe the
displayed reading. If necessary, adjust the CAL
potentiometer on the side of the sound level meter to

94.0 dB ± 0.2 dB with the small screwdriver provided.
When re-checking calibration immediately following a
measurement, the instrument should repeat the
calibration setting without further adjustment.

5.5 Re-calibration

The sound level meter is supplied factory calibrated.
As noted above, the calibration should be checked prior to and immediately after any
critical measurements, or following any prolonged storage of the instrument. In any
event, the calibration of the instrument should be verified no less than once per year.

MAX

MIN

LEVEL

Lo =

30

Med=

50

Hi =

80

Auto=

30

IEC 651 TYPE II

POWER-UP OPTIONS

AC

FAST
SLOW

80 dB
100 dB
130 dB
130 dB

coustic

Calibrator

Screwdriver

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C

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