Fluke CombiScope PM3370B User Manual page 71

3 - 52
dBm - 50Ω offset calculation:
From the Vrms offset value the dBm-50Ω offset value is calculated as follows:
dBm 50Ω offset
(
Note:
Example for attenuator setting 0.5 V/div.:
dBm 50Ω offset
dBm - 600Ω offset calculation:
From the Vrms offset value the dBm-600Ω offset value is calculated as follows:
dBm 600Ω offset
(
Note:
Example for attenuator setting 0.5 V/div.:
dBm 600Ω offset
dBµV offset calculation:
From the Vrms offset value the dBµV offset value is calculated as follows:
dBµV offset
0 dBµV = 1 µV (1.0E-6 V) at 50Ω impedance.
Note:
Example for attenuator setting 0.5 V/div.:
dBµV offset
– = 20 *
) (
P *R = 1E-3 *50
– = 20 *
– =
) (
P *R = 1E-3 *600
– = 20 *
10
= 20 * log
10
= 20 *
USING THE COMBISCOPE INSTRUMENTS
10
(
log Vrms offset 0,2236068
)
= 0,2236068
10
(
log 1,118034 0,2236068
10
(
20 * log Vrms offset 0,7745967
)
= 0,7745967
10
(
log 1,118034 0,7745967
( ⁄
Vrms offset 1.0E-6
( ⁄
log 1,118034 1E-6
⁄ )
⁄ )
= 13,9794
⁄ )
⁄ )
= 3,1875874
)
)
= 120,9691