Formula Sound SENTRY MK2 User manual

Sentry MK 2
ENVIRONMENTAL NOISE CONTROL SYSTEM
INSTALLATION INFORMATION
MK2
TheSentryMK2basicallyperformsthesamefunctionsastheoriginalFormulaSoundSentrybut
withaddedfeaturesandoptions.
•Newcasedesignprovides easier connections via cableentryknock-outsand screw terminals
•Achoiceofinternalmicrophone(suppliedfactoryfittedasstandard) or external microphone
maybe selected
•Removablecoverprovides access to all connectorsand settings.Anti-tampersealsare
provided.
•Anti-tampermicrophonecircuitryisincorporatedwithafrontpanelindicator.
•Dualmainsvoltageoperationisstandard(internallyswitchable)
General Detail
TheSentrywasdesignedtohelpsolvesomeoftheenvironmentalnoiseproblemsencounteredat
entertainmentvenuesandinworkingareas.
The unit was designed to be as versatile in use as possible and features a large bar graph
display.Althoughitsmainapplicationistocontrolmainspoweroutletsinentertainmentvenuesit
isnotrestrictedtothis application. Basically any function that can be controlledbyarelayor
switchcanbecontrolledbytheSentry. Thesemayincludedisconnectingloudspeakers,switching
passiveattenuatorstoreducesystemvolumeoractingasthetriggerintoanactiveattenuator
system.
TheSentrymayalso be used as astandalonedisplay unit indicating sound pressurelevelsorin
industrialapplicationstoswitch on warning lamps orilluminatedsignsadvising the use of ear
defenderswhenthesafenoise level is exceeded.
Itismicrophonedrivenandhasitsownbuiltin microphone.
TheSentryincorporatesthefacilitytooperateattwodifferentsoundlevelthresholdswhichmay
beselectedmanuallybya remote key switch or similar,orautomaticallybya time switch.
(Switchesnotsupplied)
TheSentryisprovidedwithconnectorstointerfacewitharangeofequipment,plusinternally
selectableoptions to make thesystem as versatileas possible.
Ourtechnicaldepartmentisalwaysonhandtoadvisewhenunusualapplicationsare
encountered.
Page 1

Operation
TheSentryfeatures a large bar-graph VUmeter with 23dB range togive a visual indication ofthe
noiselevelinavenue. Thishastheadvantageoverotherunitsinthatanyonecanseethevolume
levelandcansee how their actions arecontributingtothis level. While the meter isoperatingin
thegreensection,with even an occasional peakintothered, there is no causeforconcern.
TheSentrywilloperate within the range 80dB-120dBand may be pre-set toanywhereinthis
range. Provisionis included to operate at2 differentlevels,for instanceatdifferenttimesofday.
Thisselectioncanbeperformedmanuallyorautomaticallybya time switch. Afrontpanel
indicatorshowswhenlevel2 is selected.
Ifa mains warning lamp isconnected it will operateat the same pointas the two redsections of
themeter. Thesearelabelled“WARNING”.
Ifthenoiselevelishighenoughtolightthe“OVERLIMIT”sectionofthemeter(threeredsections)
thenoisehas exceeded the allowable limit. Ifthis is allowed to continuefor more than the settime
periodthe unit will tripand remove thepower to the contactororrelay. Visualindication of this is
providedabovetheresetbutton.
Whenthe unit is firstpowered up theRESET indicator will belit - waitfor a few secondsand
pressthere-setbutton. TheSentrywillnowbere-setand ready for normal operation.
Theactionofthetimingcircuitmeansthatcontinuallyexceeding the limit even for short periods
mayeventuallytriptheunit.
Theunithasto be manually reset torestorepowerand this will only bepossibleaftera short time.
Theresettimeis determined by the amountbywhichthe unit is driven overlimit.e.g.tripping the
unitby just exceeding thelimit will resultin a short periodof a fewseconds before reset is
possible. Tripping the unitby grossly exceedingthe limit will requirea longer periodbefore reset
is possible.
NOTE. It is important that a check is made before the unit is re-set.
Check that it is safe to do so.
Audiosystems generally need tobe powered upin a specific order. In an audio system
comprisingofdifferent components amplifiers, mixers, etc.a general rule is toswitch power
amplifiers off first and on last to avoid possible loudspeaker damage. Therefore a band or D.J.
mayneedto turn off amplification equipmentto protect loudspeakers before thepower is
restored.
Mic Tamper
Ananti-tamper circuit is incorporated whichif enabled will detectthe presence of tapeetc. placed
onthecaseabovetheinternalmicrophoneinanattempt to artificially raise the internally set
threshold.Toenablethisfunctionadjust theT.S. preset (X) on Drg 879. (turn the pre-set to
approx the 11 o’clock position. External microphones being disconnected will also be detected
bya seperate circuit. Afront panelindicatorwillshow MICTAMPER.
TheSentrywillswitch off if the MictamperorSecurity loop indicators are illuminated.
Allconnectionsandadjustmentsarelocatedbeneaththeremovablecover plate. None reusable
securitylabelsaresuppliedwitheachunittohelpensure that unauthorised tampering is detected.
Timer
Theperiod of time thatnoise “over limit”is tolerated before theunit trips outis variable over the
rangeof 10 - 70 seconds. Apre-setis provided to adjust thisshould it be necessary - the factory
settingis approx. 20seconds.
Page 2

Mounting Position
TheSentryshouldbemountedonaflatsolid surfacepreferablywhereitcan be seen by the
personsaffectedby its use (D.J., band,etc.). It should be located ina position where it cannotbe
tamperedwith,e.g. aminimumof8feet (2.5 meters) fromthefloor,ideally on a wall facingthe
noisesource. Itis not necessary to havea microphone suspended above theband or dance
floor. IftheSentry can hear the noise source above the background noise the unit canbe
calibratedaccordingly.
Avoidpositions that aretoo close tothe noise sourcee.g. in atypical concert roomwith the stage
areaatoneend theSentryshouldbepositionedcentrallyawayfromthestage ata minimum
distanceequalto the stage width. If thereis more than one sourceof noise, e.g. several
instrumentsinaband the Sentry should ideallybeata position equal distance fromeach
instrument.(seeFig1)
IdealPosition
w
“A” x “W”
Sentry Stage
At least 2.5m y
FromFloorlevel z
Fig 1
Distance“A”shouldneverbe less than distance “W”.
Poor Positioning
w
x
Stage
Position (B) y
Sentry Sentry z
Better position Poor position
Fig 2
InFig2theinstrumentsy&zwillappearloudertotheSentry than instruments w&x. Movingthe
Sentrybackaway from the stage toposition (B) will minimise theproblem
Inordertohelpsolve difficult location problems provision is now includedtoconnectaremote
microphone to the Sentry MK2. See Drg No 879 for more details.
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Cable Entry And Fixing
Read this section fully before proceeding
Customising the box. Cable entry knock outs are provided on the rear and bottom faces of the
unit,usingtherearcableentryscanresultinaveryneatinstallation. Selectthecableentry
positionstobe used and remove theappropriate knock outs. (A small flatblade screwdriver on
theperimeteroftheholewillassistprizingoutthe blanking plugs.) Remove any sharp edges that
maydamagecables or use protective grommets(not supplied)
NOTE:- Use a separate cable entry for mains connections. Always keep low voltage cables
away from mains cables and connections
Fastening the unit. The unit issecured to awall by 3 screws(not supplied). The topcentre
screwlocatesin a key hole sloton the back of theunit.
UseNo.10 or 12 screws withround heads 1.5" (38mm) minimumlength. Brick or masonry walls
willrequiredrillingandpluggingintheusualmanner.
Firstremovethecover to expose the bottommountingscrewholes, these are located inthe
bottomcorners of the case.Fit the topcentre screw 30 mmdown from therequired top case
position,leavethisscrewapprox. 1.5mm proud of the mounting face.
Theunitmaynowbe suspended on this screw while the twobottommountingscrewpositions are
markedout(ensurethat the unit is captiveonthescrew head so it cannotfall). Fitthebottom two
mountingscrews.
Checkthattheunitis secure,cannotfall,andisnot loose on the screws.
Inhighriskareassecurity screws should be utilised to prevent theunitfrombeingremoved.
Wiring For Applications Controlling The Mains Power.
All mains wiring must be installed in accordance with IEE Regulations. If after reading
these instructions you are not sure how to proceed you should seek help from a
qualified electrician.
Overview
TheSentryprovidesoutputstocontrolacontactororrelaywhichin turn will control the mains
supply. This strategy allows the Sentrytobemountedin the most suitable position for noise
measuringwhilstthemainsswitchingequipment(therelayorcontactor)canbemountedinthe
mostconvenient positionforswitchingthemainspower(fusecupboard,etc.)
(A32ampfullyfusedboxedcontactorwithlowvoltageinterface has been designed for use with
theSentryandisavailablefromFormulaSoundLtd)
Theextrasafetyandpossiblelowerinstallationcostsstemmingfromthefactthatonlylowvoltage
cableisrequiredbetween the Sentry and contactoratminimalcurrent are added benefits.
TheSentryalsoprovidesconnections to use a mains coil contactor withamaximumcoil
consumptionof60VA.
Page 4

Installation
Selectandinstallasuitablecontactor,arrangingtheinstallationtocontrolallthepoweroutletsin
thevicinity. (Ifanyare leftuncontrolleditwillnottakeverylongfortheenterprisingbandorD.J.to
findandusethem. Itisinadvisabletoarrangecontrolofonlyhalftheoutletsinavenue).
Inverylargeinstallations,itisasimplematterto make 1 contactor control many others
ofwhatevercurrentratingisrequired.
ConnectthecontactorcontrolbacktotheSentryusingappropriate cable and connections
dependingonthetypeofcontactorused.
Connections
AllconnectionstotheSentryarelocatedbeneaththelowerremovablefrontcover.Onthiscoveris
alsomountedtheresetbutton which connects to the printed circuit boardviaa2pin plug and may
be easily disconnected. See Drg No 879.for more details.
ConnecttheSentrytoasuitablemainsoutletusingtheterminalslabelled“MainsIn”andensure
thattheearth is also connected. The mainsconsumption is approximately 1amp at240V - a
5amplightingfeed could be utilised. Connect viaan isolating switch or removableplug socket
arrangementsothattheunitcanbeisolatedwhennecessary.
Foruseon120V the consumption will beapproximately2amps
ENSURETHATTHE MAINS SUPPLYISNOTTHE SAMEASTHATCONTROLLEDBYTHE
CONTACTOR. REMEMBERTHIS SUPPLYCONTROLSALLTHEPOWEROUTLETS
CONTROLLEDBYTHE CONTACTOR.
Warning Lamp
Provision to switch a mains warning lamp to a maximum of 60VAis provided. The lamp can be of
anystyleconsideredsuitablebutmusthavea maximum consumption of 60VA(60watts). Itis
connectedtothemainsoutletterminalslabelled“warninglamp”. Alternativelyarelayorcontactor
maybe used to switchother lamps asrequired. Good wiring practice shouldbe observed.
Remote Reset
Provisionfor a remote reset buttonis provided and ifthis facility is requireda momentary action
pushbutton or key switch shouldbe fitted. Site this ina Manager’sofficeor suitablelocation.
(Seeseparatedrawing (Drg No 879) givingfull connection details).
Setting The Permissible Volume Level
Adjustmentof allowable noise levelis made byadjusting the pre-setsADJ1andADJ 2. These
arelocatedbeneaththeremovablecoveratthelefthand end of the unit. They are 10-turn pre-
setstoprovidefine adjustment. ADJ1 setsthenormaloperatinglevel,ADJ2setsthelevel for a
secondthresholdwhichcanbeinitiatedremotely. An indicator on the front panel will show when
level2is selected. Take carewhenmaking adjustmentsand use a smallscrewdriver . Tryto
makeadjustmentswhen the noise level isdisplayed on the bar graphmeter as you will beableto
seethechangesdisplayed on the meter.
Theadjustmentpre-setshaveaslippingclutchattheend of travel to prevent damage. But this
cancause confusion if thepre-set is atthe end of travelas it thenappears to do nothing(this is
notusuallyaproblemonceyouknowaboutit).
Page 5

Setting The Permissible Volume Level continued
Theactualsoundpressurelevel(SPL)atwhichtheunitoperatescanonlybedeterminedby
measuringthenoiselevelusingacalibratedsoundpressurelevelmeterandadjustingtheunit
accordingly.
Alternativelytheunitmaybeadjustedusingtrialanderrorbutthisshouldbeusedonlyasa
temporarymeasureorlastresort. Measuring the sound level and setting to alimitagreedwiththe
localareaofficialisthe only recommended method.
Aninternalmeasuringmicrophoneis fitted which will be suitable for mostapplicationsbutshould
theneedariseanexternalmicrophonecanbeconnected. Theexternal microphone may be a
movingcoil type, capacitor or electret. Microphonephantom power is providedand may be
selectedasrequired. Selecta microphone with the requiredfrequencyresponseand polar
response. (Pleasetelephoneourtechnicaldepartment if help is required).
NOTES:- Iftheunitis to be used inanentertainmentvenue to control a bandordiscouse a meter
witheitheralinear scale or ‘C’ weightingresponse.
Thefrequencyresponseofthe measuring circuit of the Sentry may beselectedtobe,Linear (Flat
response),‘C’ (Conventional “C” scale) orBass (LP filter @300Hz12dB per octave slope.)
See Drg No 879
‘A’weightingisafrequencyresponsecurvethat resemblesthehumanearresponse. It is much
moresensitiveinthemid 500Hz - 5kHz region. It is not recommendedforentertainmentvenues
as it is less sensitive to the bass regions where most problems lie. An “A” weighting filter may be
fittedas a factory optionif required.
SECURITY LABELS ARE PROVIDED. THESE SHOULD BE FITTED TO
COVER THE SCREW HEADS HOLDING THE REMOVABLE COVER IN
PLACE AND WILL REVEAL ANY UNAUTHORISED ATTEMPT TO CHANGE
THE THRESHOLDS
ALWAYSFITSECURITYLABELSAFTERADJUSTMENTS HAVEBEEN MADE.
EXTRALABELSAREAVAILABLE FROM FORMULASOUND IF REQUIRED.
Rememberthattheacousticcharacteristics of a venue will change depending onthenumberof
peoplein it. Our experience has shownthat it is alwaysadvisable to take readingswhen the
venueis in use. It would bea wise precaution toallow in your costingsfor a site visitduring
openinghourstotakemeasurementsandmakefinaladjustments.
Security Loop
Provision to connect a security loop is provided. This may be required to detect open doors or
windowsthatwouldimpair the sound proofing ofabuilding,etc. Magnetically operated reed
switchesofthetypeusedinintruderalarmsaremost convenient for this application. If this facility
isnotrequireda wire link must beconnectedtoallow the Sentry to worknormally.(see Drg No
879)
Afrontpanelindicator shows if the securityloopisopened.
Tampering
Correctlylocatingtheunitoutofreachisthebest form of security.
Ifyoufindthatyouhaveproblemswithunauthorised persons tamperingwiththesettings,
security
screws are available
to replace the cover screws, a special key is also supplied for the fitting
andremovalof these screws. Contact FORMULA SOUNDsales office for more details
Page 6

Internal Settings
Severaloptionalsettingsare available internally. These areallshown on a separatedrawing
Drg No 879
Internal External Microphone Selection
Thisis accomplished by the positionof two jumper plugson pin headers. Takecare to moveboth
jumpersand ensure that they connect correctly. Thepositions are shown on theP.C.B.
External Microphone Phantom power
Phantompoweris available for capacitor andelectret microphones, two jumper plugsselect in a
similarmannertomicrophoneselection. Ensure both jumpers are moved and connected
correctly.
Weighting Selection
Thepositionofonejumperplugselectstheresponseon the measuring microphone. The
positionsareshownonthe P.C.B. Ensurethatthe jumper is seated correctly.
Special weighting options are possible -contactFormulaSound for further details.
External Microphone connection
A3way terminal strip is providedfor the connection of aremote microphone. The microphone
shouldbelow impedance and balanced andgood quality twin screened cableshould be used for
theconnections. Selectamicrophone with the desired frequencyresponseanddirectional
characteristics.
Led Indicators
Outputsare providedforremote led indicators:- MICTAMPER, LEVEL2, WARNING, RESET
REQUIRED. Ifmorethantwo leds are to beconnectedtheyshare a common terminal. Led
currentlimitingresistorsare not required. Leds may beconnecteddirectly.Theseoutputsare
alsosufficienttodrive a contactor with lowvoltageinterfaceif required.
TimerAdjustment
Theperiod of time thatnoise “over limit”is tolerated before theunit trips outis variable over the
rangeof 10 - 70 seconds. If adjustment isrequired locate the timer pre-set from DrgNo 879 and
adjustwithasmallterminal screwdriver as required. Due to the action ofthecircuityoumay have
to wait up to 70 seconds for the timing capacitor to discharge before new timer settings will take
place.
LimeTechnologies
UK
Web: noiselimiters.co.uk
Email: [email protected]
Page 7



SENTRY MK2 ADDENDUM
Sentry“A”weighting Option
An“A”weighting option is available forapplications that require it i.e.Industrial noise
applications.‘A’weighting is a frequency response curvethat resemblesthehumanear
response. It ismuchmore sensitive in the mid500Hz - 5kHz region. It isselected by placing the
weightingresponseselector in the top position.
Wherethisoption is fitted the “Bass”weighting filter is replaced bythe “A” weighting filter. Sentry
unitssupplied with this option willhave been re-labelled as“A” instead of Basson the PCB.
‘C’ weighting and Linear response are still available by using the weighting response selector.
(See Drg. 879 Section D).
REMOTE RESET SWITCHES
2 types of remote reset switch are available a push button version and a key switch version for
extra security. Both types feature a surface mount box 65mm X 65mm X 45mm depth. They
are fitted with led’s to indicate Warning and Reset. Connections are the same for both types.
Other manuals for SENTRY MK2
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