DB Measurements in AC Volts Functions, DBm Display | Fluke 187

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

Contents

Model 187 Lifetime Limited Warranty Table of Contents Model 187 Making Measurements Iii Maintenance Specifications List of Tables List of Figures Viii Contacting Fluke Safety InformationBefore You Start Safety Information WWarning Before You Start Symbols International Electrical Symbols Turning the Meter On Getting AcquaintedIntroduction Battery Considerations Automatic Power Off Low Battery Indication Automatic Backlight Off Rotary Switch Rotary Switch Pushbuttons Pushbuttons Rotary Switch Selections Position Rotary Switch Function Blue Key Function Rotary Switch Positions View MEM Button Pushbuttons Yellow Button Description Function Pushbuttons Button Description Yellow Button Function Primary Display Selecting the RangeUnderstanding the Display Bar Graph Secondary Display Display Features Number Feature Display Features Description Display Features Number 8.8.8 Number Feature Display Features Description Display Features Number 51000 FMS8888 HM8888 8.8 Using the Input Terminals Input Terminals Using Display Hold Display Hold and AutoHOLD Using AutoHOLD Using MIN MAX Model 187 Using Fast MN MX Min Max Avg Using Relative Mode REL Using Hold with MIN MAX or Fast MN MX Making Measurements Measuring Voltage Measuring AC Voltage AC Voltage Measurement DB Measurements in AC Volts Functions DBm Display Measuring DC Voltage Both AC and DC Voltage Measurements AC over DC DC over AC AC and DC Display Measuring Resistance Capacitors before measuring resistance OFF Testing for Continuity Automatically subtract this value Using Conductance for High Resistance Tests For in-circuit tests, turn circuit power off Conductance Measurement Measuring Capacitance Testing Diodes Capacitance Measurement Diode Test Electrically live circuits Measuring TemperatureShock, do not connect the thermocouples to Measuring Current Input Ranges Input Alert Feature Measuring Current Measuring AC Current Following are some tips for measuring current 11. AC Current Measurement Measuring DC Current Total current to circuit Current through one component Measuring Frequency 13. Functions Allowing Frequency Measurement Measuring Duty Cycle 14. Hz Display Measures Positive Pulse Measures Negative Pulse Measuring Pulse Width 16. Duty Cycle Display Start and Stop on Positive Slope Start and Stop on Negative Slope 18. Pulse Width Display Saved Readings Memory Using Memory & Communications FeaturesTypes of Memory Logged Readings Memory Stopping Logging Storing Saved ReadingsStarting Logging Viewing Memory Data To avoid electric shock, disconnect the test View Display MEM Using Communications 187 Clearing Memory Changing the Default Settings Selecting Setup Options Precondition Function Specific Setup SelectionsFactory Default Option Common Setup Selections Choices Adjusting the Temperature Offset Changing the Default Settings Selecting Display Resolution 3 1/2 or 4 1/2 Digits Setting the Power Off Timeout Setting the 24-Hour Clock Setting the Line Main Frequency Returning to Factory Defaults Saving Setup Options Testing 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 Compliances Physical Specifications Feature Summary Basic Specifications Detailed Accuracy Specifications 20 kHz Accuracy Function45-1 kHz KHz-100 kHz DC a 500.00 Ω Capacitance Diode Test MIN MAX AVG Frequency Counter Sensitivity Burden Voltage A, mA, µA Input Characteristics