Keithley 2100 User Manual page 76

Section 4: Front Panel Operations
The dB feature takes a DC or AC voltage measurement and displays it in decibel units that
correspond with a relative reference value. The calculation of dB is listed below:
NOTE
The dB measurement is applied to DC and AC voltage only. The relative value is adjustable (from
0dBm to 200dBm) and is stored in volatile memory.
Setting the relative reference value
You can either manually select a number for the relative reference, or let the multimeter take the
first reading (0dB):
To set the relative reference value from the front panel:
1. Press the CONFIG + SHIFT + NULL keys.
2. Use the PREV and NEXT keys to move through the digits and the up and down arrow keys
to increase or decrease the numbers to the desired value.
3. Press ENTER to set the value (refer to
Figure 4-23
Setting the relative reference value
DCI ACI
PREV
AC V AC V
DCV
DISPLAY
FILTER DIGITS
NEXT
EXTRIG HOLD
AUTO
OFF SINGL E
TRIGGER
ON
POWER
TRIGGER
To make a dB measurement from the front panel:
1. Select the measurement function by pressing one of the DCV or ACV keys.
2. Enable the dB operation by pressing SHIFT + NULL keys.
3. After enabling the dB operation, you can set or alter the dB relative value as mentioned
above.
4. Observe the displayed reading (refer to
NOTE
4-28
dB = (Input signal in dBm) - (relative value in dBm)
The Vin is the input signal and the Vref is the relative reference.
FUNCTION SETUP
4 PERIOD
2 2 2 2
PREV
FREQ CONT TEMP
LOCK
LIMIT S MX+B dBm dB
%
RATIO NULL ESC
MIN/MA X
MATH
STORE SHIFT
RECA L L L OCA L CONFIG
MEMORY
Press SHIFT + NULL again to disable this feature. The "MATH" annunciator on the
display indicates the state of a mathematical feature.
Return to
Model 2100 6 1/2-Digit Resolution Digital Multimeter User's Manual
dB = 20 x log(Vin / Vref)
or
Figure 4-23).
CAT 1000V
CAT 600V
INPUT
SENSE
V
4 WIRE
HI
RATIO
200V
REF
PEA K
LO
RANGE
3A
NEXT
INPUTS
RMS
F R
ENTER
A UTO
FRONT/REAR
3A 250V
AMP S
MENU
Figure 4-24
Section Topics
SHIFT
CONFIG
1000V
PREV NEXT
PEA K
500V
PEA K
ENTER
for the location of the keys used).
2100-900-01 Rev. D / September 2011
NULL