Fluke 189 user manual Measuring DC Voltage, Both AC and DC Voltage Measurements

Model 187 & 189

Users Manual

dB is calculated with the following formula:

dB =		Vx 
	20 * log10 		
		Vr 

•For dBm, Vr is the voltage across the reference

resistance at 1 mW. For example, Vr would be 0.7746 V with a 600 Ω reference resistance.

•For dBV, the reference voltage (Vr) is 1 V.

Measuring DC Voltage

Set up the meter for dc voltage measurement as shown in Figure 3-4. All pushbutton features are available for a standard dc volts reading.

Both AC and DC Voltage Measurements

When a dc volts function is selected, the meter can display ac and dc components of a signal separately or the combined ac + dc (rms) value.

To select separate ac and dc signal components:

•Press % once to display ac voltage in the primary display and dc voltage in the secondary display (ac over dc).

•Press % a second time to reverse the displays (dc over ac).

•Press % a third time to display the ac + dc rms value in the primary display. (FAST MN MX is unavailable in this state.)

•Press % a fourth time to return to the normal dc volts display.

Figure 3-3 shows some typical displays.

3-4