HP TM 11-6625-2779-14&P manual Level Measurement Noise Metallic Measurements, Step Procedure

Page 25

Model 3555B

Section III

Table 3-3. Level Measurement

Table 3-4. Noise Metallic Measurements

STEP

PROCEDURE

1.Turn the 3555B/ON and depress the DIAL/BAT pushbutton. The meter should indicate in the green BAT GOOD area. If it does not, replace the battery or check the power source before attempting to make any measurements. The battery test operates for internal battery, office battery or ac power source.

2.Select either TMS BRDG or TMS TERM, depending on the measurement being made. The weighting filters are not in the circuit at this time.

3.Select the impedance (FUNCTION pushbutton) to match the circuit to be tested. Select either 900 BAL or 600 BAL (VF/Nm) for frequencies between 20Hz and 20kHz. Select 600 BAL or 135 BAL (CARRIER) for balanced measurements between 1 kHz and 600kHz. Select 75 UNBAL for 75 ohm unbalanced measurements between 30Hz and 3MHz.

4.Set the RANGE switch to +30dBm. Set the RESPONSE switch to DAMP.

5.Connect the set to the line using a suitable patch cord. For balanced measurements use a cord having a 309 or 310 single plug, a 241 dual plug or banana plugs, bare wires or clip leads. For unbalanced carrier measurements (75 ohm only) use a cord having a 358 plug.

NOTE

Carrier measurements are limited to the -50dBm RANGE thru the +10dBm RANGE.

6.Down range the RANGE switch for an on-

scale indication. Level is equal to the algebraic sum of the black RANGE setting plus the black meter scale indication.

EXAMPLES:

RANGE =

-50dBm

METER =

+1dBm

LEVEL =

-49dBm

RANGE =

+20dBm

METER =

-4dBm

LEVEL =

+16dBm

3-13

STEP

PROCEDURE

1.Turn the POWER switch to ON and depress the DIAL/BAT pushbutton. The meter should indicate in the green BAT GOOD area. If it does not replace the battery or check the power source. The battery test operates on internal battery, office battery or ac power source.

2.Select either NOISE TERM or NOISE BRDG, depending on the measurement being made.

3.Select the impedance to match the circuit to be tested using the FUNCTION pushbuttons. The 900 BAL VF/Nm pushbuttons only should be used for noise metallic measurements in the frequency range of 20Hz to 20kHz. The HOLD function can be used in NOISE TERM if desired.

4.Select the appropriate weighting filters using the NOISE WTG switch.

5.Set the RANGE switch to 110dBrn.

6.Connect the set to the circuit to be tested using a suitable patch cord and down range for an on-scale indication.

7.Observe the meter fluctuations for two or three minutes and take a reading where the meter pointer appears to be most of the time, disregarding any occasional peaks.

NOTE

For rapidly fluctuating noises such as atmospheric noise or switching noise, operate the RESPONSE switch to DAMP and read the level of the most frequently occurring peaks.

8.Noise level is equal to the sum of the blue RANGE switch setting in dBrn and the indication on the blue meter scale in dBrn.

EXAMPLE:

 

 

RANGE

=

40dBrn

METER

=

+5dBrn

NOISE LEVEL

=

+45dBrn

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Contents HEADQUARTERS, Department of the Army TM 11-6625-2779-14&P Reporting Errors and Recommending ImprovementsTechnical Manual Headquarters Department of the Army NSNReplaceable Parts List of Tables List of IllustrationsIii Section Introduction Maintenance Forms, Records, and ReportsScope Destruction of Army Electronics Materiel Administrative StorageReporting Equipment Improvement Recommendations EIR Items Comprising an Operable Equipment Voice Frequency Level Measurements 20Hz to 20kHz SpecificationsSection General Information Introduction SectionAccessory Equipment Supplied Accessory Equipment SuppliedInstrument Identification BAL ModificationWarranty Exception Section Installation InspectionPower Requirements BatteryCover Removal Installation and Removal of BatteryBattery Controls Connectors IndicatorsSection Operating InstructionsFront Panel Controls, Indicators, and Connectors Front, Side and Rear Pane Side Panel Controls and Connectors Level Measurements Level and Noise MeasurementsPage Noise Measurement Applications Recorder CompatibilityRecorder Compatibility Chart Transmission Loss Measurements Identifying Noise CharacteristicsCrosstalk Measurements Crosstalk Correction FactorMeasurements in DBC 0dBm Reinstall the set in its caseInput jacks are connected in parallel. If a 600 ohm 135 BALLevel Measurement Noise Metallic Measurements Step ProcedureRecorder Calibration Noise-to-Ground Measurements Balance MeasurementExample Transmission Loss MeasurementSection Theory of Operation Introduction Block Diagram DescriptionSimplified Dial BAT Function Detailed Circuit DescriptionRange Attenuator A2 Input Amplifier A3. Schematic NoFILTERS. Schematic No Setting AttenuationRange Attenuator Pads UsedKHz Flat and Program Weighting Curves C-MSG and 1SkHz Flat Weighting Curves DETECTOR. Schematic No Meter AMPLIFIER. Schematic NoPower Supply and Series Regulator Schematic No Instrument Recommended Type Required Characteristics Model Section Maintenance IntroouctionFactory Selected Values BAL ConversionLevel Accuracy Checks Performance ChecksFunction CARRIER, 75 Unbal TMS, TermRange Unbal Carrier Accuracy CheckFrequency 30Hz to 1MHz 100Hz to 600kHz 1MHz to 3MHz20Hz to 20kHz 40Hz to 15kHz 100Hz to 20kHz 100Hz to 15kHz Return Loss CheckReturn Loss Test Set-Up Filter Response Checks Filter Response ChecksMSG dBm 3kHz Flat dBm 15kHz Flat dBm Program dBm Bridging Loss Input BalanceTMS Brdg Input TMS BrdgPower Supply Check Adjustment and Calibration ProcedureUnbal Calibration Attenuator CalibrationCommon Mode Adjustment Frequency Response AdjustmentBalance Check Troubleshooting Procedures Assembly RemovalFilter Calibration Troubleshooting Tree Dial BAT Front Panel Trouble AnalysisFunction Troubleshooting Front Panel TroubleshootingRange Troubleshooting Front Panel Trouble Analysis ContdFilter Troubleshooting Troubleshooting Input AmplifierTroubleshooting the Meter Amplifier and Detector Defective FunctionFunction Input Jacks DIAL/AC MON Jacks Function Switch Resistance ValuesTip to Ring Tip to Ground Ring to Ground Brdg Term10. Resistance Checks 11. Factory Selected ValuesRange dBm Pin 1 to Pin 2 to Description Check Performance Check Test CardCarrier 75 Unbal Level Accuracy Check Carrier 135 BAL Level Accuracy CheckCarrier 600 BAL Level Accuracy Check Performance Check Test Card ContdFilter Response Checks MSG Return Loss CheckProgram Bridging Loss CheckOrdering Information Section Replaceable Parts Introduction03555-66507 PC Board Assy function Replaceable Parts03555-66508 Board Assy amplifier Replaceable Parts ContdA3 Contd 03555-66506 PC Board Assy filter A4 Contd Chassis Mounted Components Miscellaneous Chassis Mounted Components ContdMiscellaneous Contd Part Number National Stock Number Cross Reference Index Replacement National Part Stock Number FscmFscm National Stock NumberPage Model 3555B Appendix a Code List of Manufacturers Functional Block Diagram Circuit DiagramsSchematic Diagrams Reference DesignationsSection Model 3555B 7-4 Functional Block Diagram7-6 A1 Function Assembly Schematic and Component Location7-8 7-10 A4 Filter Schematic and Component Location11/7-12 References Appendix aMaintenance Function Maintenance Allocation Section I. Introduction GeneralAppendix B Column EntriesRemarks Sec Tool and Test Equipment Requiremen ts SecAudio Level Meter TA-885/U REF Code Number TM 11-7725-2779-14&PManual Backdating Changes Appendix CTransmission and Noise Measuring SET Government Printing Office 1980-603-128/66 Delete CR6 across M1Chief of Staff General, United States ArmyMajor General, United States Army Adjutant General Active ArmyPage PIN
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