User manual

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AppendixA:
Calibrationmode:
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Warning: Only trained qualified personnel may open covers and performs this
procedure.
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To calibrate the U70F a precision, balanced output, amplitude jitter‐free sine‐wave
enerator,asmallPhilipsscrewdriver,andaverysmallflat‐head screwdriver areg
necessary.
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Step1:Turn‐offthepowerswitchlocatedontheback‐panel.Disconnectthemainscord.
smallPhilipsdriver.
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Step2:Openthetop‐coverafterremovingallscrewswitha
Step3:Engageallfourswitchesonthefront‐panel(labeledPEAK,HOLD,RANGE,andBAR)
Step4:Re‐connectthemainscableandturnpowerbackon
Step5:Disengagethetwoswitchesinthemiddle(labeledHOLDandRANGE)duringthe
self‐test and calibration cycle. The U70F will enter calibrationmodeafterthe
completionoftheself‐test.
Step6:Applythedesiredbalancedinputsignal(1kHzsine‐wave),1.23Vfor+4dBuorany
other level between+2dBu and +20dBu. The display will either show all yellow
LEDs(‐39dBto+20dB]illuminatedifthelevelistoolow,allgreenLEDs[‐9dBto
0dB]iftheleveliscorrect,orallredLEDs[+1dBto+10dB]ifthelevelistoohigh.
Step7:AdjusttheLevelcontrolslocatedonthemeterPCBscounter‐clockwiseifthelevel
istooloworclockwiseifthelevelistoohigh.Theleveladjustmentcontroltakes
10turnfrommaximumtominimum,sopleasebepatientandkeepturning.The
.1%(+‐1dBisabout+‐procedureallowsacalibrationaccuracyoflessthana+‐0
10%).
tep8:Pressanybuttontoreturntothenormaloperatingmode.
tep9:Turntheinstrumentoff,disconnectpowerandputthetop‐coverbackon.
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