Casella-cel CEL-281 Manual de usuario

CEL-281COMPUTING NOISEDOSIMETEROperator's HandbookDocument 060112Issue: 4BMarch 1996archive DocumentforDiscontinued Instrument

920066920067If the display blinks,remains blank, or LOWBAT is indicated: eitherthere is insufficientpower or the batteriesare inserted incorrectly(see

Provided the CEL-281 is not in calibration delay mode or calibrationmode, and the display is switched ON, it can be used as follows to ob-tain and dis

4. Change the time weighting in use as detailed inSection 4.7.1.5. Provided the instrument is not logging data, press the keyto change the frequency w

criterion levels can be accepted for use, i.e. criterion levels≥threshold level as described in Section 2.2.2 and shown inTable 1.9. Press the key aga

enter the fully operational state with the display switched ON,(with or without data logging) as described in Chapter 4.If the instrument has just bee

If overloading has occurred, the display will indicate the per-centage of the elapsed time spent overloaded.6. Press the key to obtain underrange info

9. Press the key to see the earliest time or date at which the200 Pa level was exceeded.10. Press the key to display the time.11. Press the key to dis

2. Press the key to enter the distribution operational area.If data is being logged, logging will continue uninterrupted, butthe display will change t

4. Press the key to display the relevant cumulative percentvalues.5. Press the key to display the relevant probability percentvalues.6. Then press eit

1. Load and/or check batteries, perform a field accuracy check(acoustic calibration), select time and frequency weightings, andenter the fully operati

1 min. slow max Maximum SPL taken over a 1 minutesampling period with slow response,1 min. imp. max Maximum SPL taken over a 1 minutesampling period w

4. Load four AAA orLR03 batteriesinto the holdersupplied, accord-ing to polaritiesshown on thebottom of theholder, then in-sert it into thebattery com

5. Press the key to display the relevant dB level.6. Press the or keys to select respectively, the next lateror earlier cell in the currently displaye

The dosimeter is now operating as a sound level meter, indi-cating the instantaneous A-weighted Fast SPL on the main dis-play, with the current time c

The main display is now indicating A-weighted Slow SPL.13. Press the key a sixth time.The main display is now indicating A-weighted Fast Max, and ifth

5.6.3 Measuring %Dose and P%Dose1. Switch the CEL-281 ON.2. Slide the CEL-6012 Keypad on to the dosimeter.3. Wait about 30 seconds until TC= , , or is

(Q=3 is normally used in ISO measurements of noise dose,while Q=5 is specified for USA OSHA estimates of the risk ofhearing loss.)8. Inspect the curre

13. Press the key again to see the result of dose calculationusing the new threshold level.5.6.4 Finding Amount of Time Spent Above aSpecified Level1.

6. Press the or keys to step forwards or backwardsthrough the series of cells to reach the cell corresponding to thespecified level.7. Press the key t

6. Hold down the key and press the key once.Depending on whether time or date was inspected last, themain display indicates the first time or date at

6 PRINTING HARD COPY REPORTSIt is possible to download a "subset" of the contents of the CEL-281Dosimeter store to a dot matrix printer via

3. Carefully remove the front cover. All circuitry is retained in therear cover.4. Set the two DIP switches to produce the required report format,refe

4. If an incorrect time weighting for the required measurements isindicated at "TC=?", go to Section 1.3.3: Set Time Weighting.5. If an inco

Paper end: Valid,Auto linefeed: Off (The dosimeter sends a linefeed),Skip overperforation: Invalid,SLCT IN Internally fixed,Printer mode Centronics.6.

4. Either: If the dosimeter is switched ON and logging data, pressthe + key combination to stop logging, then go tostep 5.Or: If the dosimeter is curr

CEL 281 ISO ReportInstrument I.D. Number : 000000Subject : MachinistLocation : Machine Shop 2dd/mm/yyhh:mmLogging Calibration:01/01/9100:31Logging Sta

1401351301251201151101051009590858075708.45time------>1 min Leq920069dB Level -- -- -- >Figure 22: Portion of graphical plot from ISO hard copyP

7 TECHNICAL INFORMATION7.1 Schedule of PartsA complete "CEL-281 Computing Noise Dosimeter" consists only of:CEL-281 Noise Dosimeter, include

7.2 Replacing The MicrophoneCautionThis procedure should be performed only bysuitably qualified personnel.If the microphone or connecting cable become

The connector is keyed so that the plug can be inserted only thecorrect way.7. Carefully replace the upper circuit board.Locate the three 3-pin connec

10. Press the ON/OFF switch in to latch the instrument ON (seeSection 4.1).The instrument will go through its self checking program.11. Push the micro

pressure, the CEL calibrators generates a nominal 1 kHz signalwith a level of 114.0 dB at the microphone. The dosimeter dis-play should indicate 114.0

18. Using a slim screwdriver, reach through the hole in the uppercircuit board and adjust the trim potentiometer on the lowerboard (shown in Figure 23

5. Install the keypad.If the 20 s delay has elapsed before the cover and keypad havebeen installed, CAL stops blinking and the instrument becomesfully

7.3 SpecificationType:Noise Dosimeter according to ANSI S1.25-1978 Class 2A & 2C*,Personal Sound Exposure Meter according to IEC 1252:1993 and BS

Reference frequency:1kHz.Reference direction:Perpendicular to microphone diaphragm.Reference SPL & calibration integration time forsound exposure:

CEL-6225 Dust Cover has no measurable effect on acousticperformance of microphone.Electrical substitution of microphone input forcalibration:Not recom

Stored & displayed parameters:Level information:Sound pressure level (dB) with Fast time weighting,Sound pressure level (dB) with Slow time weight

6 different criterion levels, and 5 different threshold levels.Memory capacity: 14 hours*.Time information:Date and time,Elapsed time,Proportion of ov

Digital output:CEL low-power Interface, 4800 baud.Dimensions:Overall dosimeter plus keypad:150 x 83 x 41 mm, 310 g complete with batteries and battery

8 MANUFACTURERS SERVICING &WARRANTY ARRANGEMENTSIn order to ensure its rigid conformity with the requirements of the speci-fication, this instrume

In addition, CEL Instruments has a NAMAS accredited laboratory No.0237 which is able to perform certain acoustic calibrations with traceabil-ity to U.

C-RETINFReason for Return/Nature of Fault DateCustomer ReferenceCustomer NameAddressPhone No.Contact NameInstrument TypeSerial NumberInstrument TypeSe

Service & Warranty_

WarningTo prevent damage, DO NOT EXERT FORCE onthe flexible crosspiece when removing themicrophone from the calibrator coupler.PULL ONLY on the rigid

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1. Press the key to start data logging.The instrument starts to store data samples at the beginning ofthe next whole clock minute.2. Press the key to

4. Press the key once.5. If some other value than 3 is shown at "Q=?", press thekey enough times to obtain "Q=3".The main display

The main display now indicates sound exposure level in Pa h,and if the instrument contains stored data or is logging data, alevel will be given.1.7 Re

6. If necessary, view the current threshold level (at "Thr") by press-ing the key once.7. If necessary, press the key slowly sufficient time

6. Press the key once.The main display indicates the last time or date when the200 Pa level was exceeded.7. If time is indicated, press the key once t

Supplementary Information - July 1996Revised Microphone ArrangementsSince this handbook was prepared, a redesigned microphone arrange-ment has come in

Getting Started_

2 INTRODUCTION TO THE CEL-2812.1 IntroductionThe CEL-281 Computing Noise Dosimeter stores all of its parameters si-multaneously, so the operator may n

MealTime (hours)LevelLevelTime (hours)LevelTime (hours)LevelMachine noise atSLM like CEL-231 orvariations in level is bestMachine noise with largemeas

Health Authority regulations OSHA 1910.95 "Occupational Noise Expo-sure".The CEL-281 is intended to be worn by an individual so that its mic

The keypad can be removed to eliminate the danger of accidentally re-setting the instrument or losing measurements. This will also preventunauthorised

Both terms are in common use, but the most recent international stand-ards specify sound exposure.The value of sound exposure measured (E) is normally

At levels below the First Action Level (1.0 Pa h - equivalent to 85 dB(A)for 8 hours) "reasonably practicable" noise reductions should be ma

Table 1: Valid pairs of criterion and threshold levelsℵℵℵℵℵℵℵℵℵℵℵℵℵℵℵℵℵℵ2.2.3 ThresholdMost sound exposure legislation requires that all noise measure

Results obtained by various researchers indicate that when the risk ofhearing damage is being considered, less emphasis need be placed onthe energy co

2.2.5 Noise DoseNoise dose is not an absolute measurement but a percentage of the rec-ommended maximum daily personal noise exposure.In this way, 100%

Contents OverviewGetting Started ...Chapter 1Introduction to The CEL-281 ...Chapter 2How it Works ...Chapter 3Preparation for Use ...

A Projected Sound Exposure can be calculated when a sample ex-posure has been obtained over a period that is different from the stand-ard eight hour w

In the field of noise measurement, it is important to know the amount oftime spent at a given noise level (known as "on time"), or the amoun

10%20%30%40%50%60%70%80%90%100%10%5%Probability%Cumulative%L90L50L10dBLLMAXMINdB91000610065%70 80 90 110 120 130 140Figure 3 Comparison of probability

1 min. L :Lwith Q = 3 taken over a 1 minutesampling period,10 s L:Lwith Q = 3 taken over a 10 secondsampling period,1sL:Lwith Q = 3 taken over a 1 sec

1 min. slow max: Maximum SPL taken over a 1 minutesampling period with slow response,10 s fast max: Maximum SPL taken over a 10 secondsampling period

3 HOW IT WORKS3.1 Principle of OperationThe CEL-281 consists of a Type 2 sound level meter (IEC 651 and ANSIS1.4 1983) with very fast time weighting,

TimerCALDelayCalibrationFully OperationalCheckBatterySetTime WtgSetFreq Wtg20 secondLevel DoseDistributionProfileTime Info.Press RundBPa h%DoseP%DoseS

calibration delay period, during which the operator can elect to perform acalibration. If no calibration is initiated within this period, the instrume

able. Equivalent noise levels (L ) are also available, calculated with sev-eral different averaging periods.3.1.5 ProfileThis area calculates and stor

Signals from the microphone are amplified and passed through an A- orC-weighting circuit, as selected by the operator. Both weightings complywith the

Contents ... Page

it into logarithmic form and transmits it into the digital section of the in-strument where all subsequent manipulations are performed.3.2.2 Digital S

a store identity number between 1 and 20,odd numbers show start times, and evennumbers show stop times (Section 3.3.9).All times use the twenty-four h

RUN Either: the instrument is waiting to pass thenext full minute of time before starting to logdata, as described in Section 3.3.4.Or: the instrument

This line may also include an additionalidentifying message: for example or.% Display is showing proportion of elapsed timein under or over range cond

The microprocessor also controls the storage and transmission of calcu-lated and measured data. The 32 kbyte EPROM contains computing andcontrol progr

All two-function keys in the keypad have a toggle operation, i.e. press forone of the functions indicated then press again for the other function,whil

In some operational areas, white keys alsohave an automatic repeat function when helddown.When pairs of keys have to be pressed to implement a command

Number of hourswith display OFFwhile not logging________________6+Number ofhours loggingdata or withdisplay ON≤ 163.3.2 Dose K

Similarly, pressing the key displays the current thresholdlevel, while pressing the key again selects the next from a se-ries of up to five threshold

CautionWhen the instrument is restarted with thekey after data logging has been stopped bypressing the + keys simultaneously,the memory contents are c

Contents (continued) ... Page

against a known acoustic level applied by an external calibratorsuch as the CEL-282. The actual adjustment is in increments of0.05 dB, but the display

When the instrument is stopped, (i.e. the + com-bination has been pressed so that no logging is taking place),and in consequence is still fully operat

While average noise levels are being displayed, pressing thekey allows the results to be obtained from four differentexchange rate values (Q). The val

3.3.6 Frequency Weighting Key(grey two function-key: changes frequency weighting used)While in calibration-delay or calibration modes, when theinstrum

When the instrument is fully operational and the instrumenthas been switched off since the distribution area was last in-spected, pressed alone, this

mulative percent, while a second press selects dB. Similarly,pressing once selects the lower (PROB%) command anddisplays probability percent, while a

grams showing cumulative percent and probability percent areillustrated in Figure 9.3.3.8 Profile Key(beige three-function key: yields profile informa

10 s slow max: Maximum SPL taken over a 10 secondsampling period with slow response,10 s imp. max: Maximum SPL taken over a 10 secondsampling period w

1 s slow max: Maximum SPL taken over a 1 secondsampling period with slow response, withresults stored for only the most recent hour,1 s imp. max: Maxi

CautionWhen delayed start and stop times and dateshave been set, ANY changes to the real timeclock disable their operation, and will requirethat all d

Contents (continued) ... Page

In any other display mode, this key combination selects theupper (SET) command on the key, cancels the other mode sothat the time and date can be set.

Start times are identified by an odd numbered store location,while stop times have an even number.Start and stop times are displayed in nn:hh:mm forma

Then moving the cursor off the display (either to left or right)selects the start or stop date which can also be edited. Tomove from one store locatio

+ (both keys pressed simultaneously)While in calibration delay or calibration modes or when thedisplay has been switched off, this key combination wil

Q = 3, 4, 5, and 6. The key may also be used when bothand keys have been used to change criterion or thresholdlevels in the current calculations.Howev

(yellow key: enables results to be calculated with differentthreshold levels)This key is active only while %Dose, Projected %Dose or Lvalues are being

Under range count,Elapsed time in seconds.Similarly, the following noise information is stored while the instrumentis switched OFF.Histograms (based o

Connection with the CEL-6012 Keypad (or with a PC) is accomplished viathe 15-line connector of the built-in CEL low-power interface bus.1 Keypad2 Seri

All communication is at CMOS logic levels, nominally 0 V and 5.0 V.The connector is located behind a sliding panel in the bottom of the in-strument. F

When the battery voltage falls to 4.2 V, the LOW BAT message ap-pears on the display, and the batteries should be replaced (see Sec-tion 4.3).How It W

4 PREPARATION FOR USEAs the CEL-281 Dosimeter measures and stores all parameters simulta-neously, it can be operated using stored or default settings

+ means while holding down, also press to obtainthe required command. The first key pressed in any combination will bethe first read and acted upon by

Indication of calibration delay mode, displayblinks for 20 seconds.Instrument now operational, shows currenttime weighting and frequency weighting.5.

6. When necessary, carefully remove the keypad from the CEL-281by sliding it downwards, until it is clear of the grooves in thesides of the dosimeter

Correct connection and polarity of the batteries is achievedONLY when the holder is inserted with this orientation.6. Replace the battery compartment

6. If the instrument is fully operational but the display has beenswitched OFF, press the key to switch the display ON,then go to step 8.7. When the i

Normally, calibration will be undertaken using either a CEL-282 AcousticCalibrator (IEC 942 Class 2L) or a CEL-284/2 Acoustic Calibrator (Class1L), bo

Again, make sure that microphone is correctly seated againstthe shoulder in the base of the cavity, noting that to aid re-moval, the coupler is design

8. When the instrument is logging data (with RUN legend dis-played continuously), press the + keys simultane-ously to stop logging.The instrument reve

However, the calibration of the instrument may have changedsince it was last checked due to variations in the ambient condi-tions. For altitude and en

NOYESAreCurrent Time & DateSetSet Time WeightingAre ThereBatteries In TheCEL-281Load BatteriesIsBattery VoltageOK(Section 6.3)Replace Batteries(Se

14. If it is required to change the time weighting in use, follow theinstructions in Section 4.7.1.15. If it is not to be used immediately, switch the

2. If the instrument is switched OFF, switch the power ON asdescribed in Section 4.1.The ON legend will appear on the display.3. If the CEL-6012 Keypa

8. When the instrument is logging data (with RUN legend dis-played continuously), press the + keys simultane-ously to stop logging.The instrument reve

14. Press the and keys to move the blinking cursor alongthe line of characters to the left or right to select another digitfor editing.Moving beyond t

All entries must be made in order: i.e. entries in higher numbered storelocations must be for later times and dates. Once the entry in the laststore l

6. Press the and keys to change the indicated digit oneunit at a time.7. Press the and keys to move the blinking cursor alongthe line of characters to

With the following formula, an estimate can be made whetherthere will be sufficient battery life at room temperature to per-form any particular loggin

4.7 Making Preliminary SettingsWhen the dosimeter is switched ON and operated, it will use either thedefault settings set at the factory or settings r

4. If the instrument is already fully operational but the display hasbeen switched OFF, press the key to switch the displayON, then go to step 8.5. If

(Impulse) symbols (see Section 3.2.2), depending on whichtime weighting is currently set.9. Press the or keys to change the time weighting to therequi

1 GETTING STARTEDIt is not necessary to re-program theCEL-281 each time it is used !In fact, if the settings for frequency weighting and time weightin

5. If the instrument is fully operational while the RUN legend isdisplayed continuously to indicate that data is being logged, goto step 6, but note t

4.8 Starting And Stopping Data LoggingIn order to generate noise distribution histograms, calculate noise dosevalues, and produce noise profile time h

4. If the instrument is in calibration delay mode or calibrationmode, if necessary perform a field accuracy check (acoustic cali-bration) according to

The RUN legend is displayed, and the instrument will start tostore samples of data at the beginning of the next whole m-inute. The instrument continue

The RUN legend is extinguished and the instrument reverts tofully operational mode with no data being logged.All preliminary set up operations and com

Preparation_

5 OBTAINING REQUIRED RESULTSProvided the CEL-281 Computing Noise Dosimeter has been preparedfor use as detailed in Chapter 4, it will store ALL parame

If the instrument has just been calibrated or the 20 secondcalibration delay period has elapsed, it will enter the soundlevel meter measurement area a

5. Provided the instrument is not logging data, if necessary, pressthe key to change the frequency weighting in use (see Sec-tion 4.7.2).6. While soun

8. While average noise levels are being displayed, press thekey to show the currently used threshold level on the main dis-play.9. If necessary, press