DB Measurements in AC Volts Functions, DBm Display | Fluke 189

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 189 user manual DB Measurements in AC Volts Functions, DBm Display

Contents

Model 187 Lifetime Limited Warranty Table of Contents Making Measurements Model 187 Iii Specifications Maintenance List of Tables Model 187 List of Figures Viii Safety Information Before You StartContacting Fluke WWarning Safety Information Before You Start International Electrical Symbols Symbols Getting Acquainted IntroductionTurning the Meter On Automatic Power Off Battery Considerations Automatic Backlight Off Low Battery Indication Rotary Switch Rotary Switch Pushbuttons Pushbuttons Blue Key Function Rotary Switch Selections Position Rotary Switch Function View MEM Rotary Switch Positions Button Pushbuttons Yellow Button Description Function Yellow Button Function Pushbuttons Button Description Selecting the Range Understanding the DisplayPrimary Display Secondary Display Bar Graph Display Features Number Feature Display Features Description 8.8.8 Display Features Number Display Features Description Number Feature FMS8888 HM8888 8.8 Display Features Number 51000 Input Terminals Using the Input Terminals Display Hold and AutoHOLD Using Display Hold Using MIN MAX Using AutoHOLD Model 187 Min Max Avg Using Fast MN MX Using Hold with MIN MAX or Fast MN MX Using Relative Mode REL Measuring Voltage Making Measurements AC Voltage Measurement Measuring AC Voltage DBm Display DB Measurements in AC Volts Functions Both AC and DC Voltage Measurements Measuring DC Voltage AC and DC Display AC over DC DC over AC Capacitors before measuring resistance Measuring Resistance OFF Automatically subtract this value Testing for Continuity Using Conductance for High Resistance Tests For in-circuit tests, turn circuit power off Conductance Measurement Measuring Capacitance Capacitance Measurement Testing Diodes Diode Test Measuring Temperature Shock, do not connect the thermocouples toElectrically live circuits Input Ranges Measuring Current Measuring Current Input Alert Feature Following are some tips for measuring current Measuring AC Current 11. AC Current Measurement Measuring DC Current Current through one component Total current to circuit 13. Functions Allowing Frequency Measurement Measuring Frequency 14. Hz Display Measuring Duty Cycle Measures Negative Pulse Measures Positive Pulse 16. Duty Cycle Display Measuring Pulse Width Start and Stop on Negative Slope Start and Stop on Positive Slope 18. Pulse Width Display Model 187 Logged Readings Memory Using Memory & Communications FeaturesTypes of Memory Saved Readings Memory Storing Saved Readings Starting LoggingStopping Logging To avoid electric shock, disconnect the test Viewing Memory Data MEM View Display Clearing Memory Using Communications 187 Model 187 Selecting Setup Options Changing the Default Settings Option Function Specific Setup SelectionsFactory Default Precondition Choices Common Setup Selections Adjusting the Temperature Offset Changing the Default Settings Setting the Power Off Timeout Selecting Display Resolution 3 1/2 or 4 1/2 Digits Setting the Line Main Frequency Setting the 24-Hour Clock Saving Setup Options Returning to Factory Defaults Maintenance Introduction General MaintenanceTesting the Fuses Replace F2 if Replace F1 if Displayed Replacing the Batteries Battery and Fuse Replacement Replacing the Fuses User-Replaceable PartsCase of Difficulty MP8 MP9 Safety and Compliances Specifications Physical Specifications Feature Summary Basic Specifications Detailed Accuracy Specifications KHz-100 kHz Accuracy Function45-1 kHz 20 kHz DC a 500.00 Ω Capacitance Diode Test MIN MAX AVG Burden Voltage A, mA, µA Frequency Counter Sensitivity Input Characteristics