30
To set the reference impedance, perform the following steps:
1. Press
Shift
→
for dBm math operation and the present reference value is displayed:
REF
：
0000
2. Use
and
keys to choose a numerical place and use
and
keys to
increment or decrement the digits. Enter a value from 1Ω
to 9999Ω.
3. Press
(ENTER) to confirm the reference impedance, the message
―
SAVED
‖
will be displayed
for a moment. TH1942 returns back to the measurement status.
4. TH1942 will display the result of the dBm calculation.
If you want to change the impedance reference value after the dBm function is enabled, you can take
actions as below:
1. Press
Shift
→
to enter the menu on the menu level,
―
A: MATH MEU
‖
will be displayed.
2. Press
to move down to the command level within the MATH MEU,
―
5: dBm REF
―will
be
displayed.
3. Press
to enter the parameter level and the present impedance reference value will be
displayed: REF: 0000.
4. Use
and
keys to choose a numerical place and use
and
keys to
increment or decrement the digits. Enter a value from
1Ω
to 9999Ω.
5. Press
(ENTER) to confirm the reference value, the message
―
SAVED
‖
will be displayed for a
moment, and TH1942 will return to the command level. Press
to cancel the reference value
input, TH1942 returns back to the command level without changing the reference value.
6. Press
Shift
→
key to exit the menu and return to the dB math operation status.
NOTES: The reference impedance and input impedance mentioned in this chapter are totally
different. Input impedance is inherent in the instrument and could not be changed via
foregoing methods.
dBm is valid for both positive and negative DC voltage.
The percent math operations are applied after the dBm or dB math.
