Fluke 187 user manual DB Measurements in AC Volts Functions, DBm Display

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Making Measurements

Measuring Voltage 3

dB Measurements in AC Volts Functions

The two ac volts functions allow you to display readings as deviations in dB (decibels) above or below an established level.

Set up dB measurements with the following procedure:

1.Make an ac volts measurement to be used as a reference point.

2.Press % to select dB. The dBm (or dBV) value appears in the primary display and the ac volts reading appears in the secondary display. A typical dB display appears in Figure 3-2.

3.Press % again to switch the ac volts and dB readings. Press % a third time to turn dB off.

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Figure 3-2. dBm Display

Normally, dB is measured as dBm, which is a measure of decibels relative to 1 milliwatt. The meter assumes a resistance of 600 Ω in making this calculation. This resistance can be set for any value from 1 to 1999 Ω , using the meter’s setup capabilities (see Chapter 5.) When set to other than 600 Ω the dBm reference resistance appears in the Index Display. (See Figure 2-4, item 17.)

Note

If dBm is displayed, check that the reference resistance value closely matches the impedance of the system being measured.

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Contents Model 187 Lifetime Limited Warranty Table of Contents Model 187 Making MeasurementsIii Maintenance SpecificationsList of Tables List of Figures Viii Contacting Fluke Safety InformationBefore You Start Safety Information WWarningBefore You Start Symbols International Electrical SymbolsTurning the Meter On Getting AcquaintedIntroduction Battery Considerations Automatic Power OffLow Battery Indication Automatic Backlight OffRotary Switch Rotary SwitchPushbuttons PushbuttonsRotary Switch Selections Position Rotary Switch Function Blue Key FunctionRotary Switch Positions View MEMButton Pushbuttons Yellow Button Description Function Pushbuttons Button Description Yellow Button FunctionPrimary Display Selecting the RangeUnderstanding the Display Bar Graph Secondary DisplayDisplay Features Number Feature Display Features Description Display Features Number 8.8.8Number Feature Display Features DescriptionDisplay Features Number 51000 FMS8888 HM8888 8.8Using the Input Terminals Input TerminalsUsing Display Hold Display Hold and AutoHOLDUsing AutoHOLD Using MIN MAXModel 187 Using Fast MN MX Min Max AvgUsing Relative Mode REL Using Hold with MIN MAX or Fast MN MXMaking Measurements Measuring VoltageMeasuring AC Voltage AC Voltage MeasurementDB Measurements in AC Volts Functions DBm DisplayMeasuring DC Voltage Both AC and DC Voltage MeasurementsAC over DC DC over AC AC and DC DisplayMeasuring Resistance Capacitors before measuring resistanceOFF Testing for Continuity Automatically subtract this valueUsing Conductance for High Resistance Tests For in-circuit tests, turn circuit power off Conductance Measurement Measuring Capacitance Testing Diodes Capacitance MeasurementDiode Test Electrically live circuits Measuring TemperatureShock, do not connect the thermocouples to Measuring Current Input RangesInput Alert Feature Measuring CurrentMeasuring AC Current Following are some tips for measuring current11. AC Current Measurement Measuring DC Current Total current to circuit Current through one componentMeasuring Frequency 13. Functions Allowing Frequency MeasurementMeasuring Duty Cycle 14. Hz DisplayMeasures Positive Pulse Measures Negative PulseMeasuring Pulse Width 16. Duty Cycle DisplayStart and Stop on Positive Slope Start and Stop on Negative Slope18. Pulse Width Display Saved Readings Memory Using Memory & Communications FeaturesTypes of Memory Logged Readings MemoryStopping Logging Storing Saved ReadingsStarting Logging Viewing Memory Data To avoid electric shock, disconnect the testView Display MEMUsing Communications 187 Clearing MemoryChanging the Default Settings Selecting Setup OptionsPrecondition Function Specific Setup SelectionsFactory Default OptionCommon Setup Selections ChoicesAdjusting the Temperature Offset Changing the Default Settings Selecting Display Resolution 3 1/2 or 4 1/2 Digits Setting the Power Off TimeoutSetting the 24-Hour Clock Setting the Line Main FrequencyReturning to Factory Defaults Saving Setup OptionsTesting the Fuses MaintenanceIntroduction General Maintenance Replace F2 if Replace F1 if Displayed Replacing the Batteries Battery and Fuse Replacement Case of Difficulty Replacing the FusesUser-Replaceable Parts MP8 MP9 Specifications Safety and CompliancesPhysical Specifications Feature Summary Basic Specifications Detailed Accuracy Specifications 20 kHz Accuracy Function45-1 kHz KHz-100 kHzDC a 500.00 Ω Capacitance Diode Test MIN MAX AVG Frequency Counter Sensitivity Burden Voltage A, mA, µAInput Characteristics