Keithley 2010 User Manual

Calculating dB characteristics accuracy
The relationship between voltage and dB is as follows:
As an example of how to calculate the actual readings limits for dB with a user-defined V
REF
of 10V, you must calculate the voltage accuracy and apply it to above equation.
To calculate a -60dB measurement, assume 10mVRMS for a V
REF
of 10V. Using the 100mV
range, one-year, 10Hz - 20kHz frequency band, and SLOW rate, the voltage limits are:
Accuracy = ±[(0.06% of reading) + (0.03% of range)]
±[(0.006 × 10mV) + (0.0003 × 100mV)]
±[6µV + 30µV]
±36µV
Thus, the actual reading accuracy is 10mV
±
36µV or 10.036mV to 9.964mV. Applying the
voltage reading accuracy into the dB equation yields:
Thus, the actual reading accuracy is -60dB + 0.031213dB to -60dB - 0.031326dB.
dBm and dB for other voltage inputs can be calculated in exactly the same manner using
pertinent specifications, ranges, and other reference voltages.
Additional derating factors
In some cases, additional derating factors must be applied to calculate certain accuracy
values. For example, an additional derating factor must be added for DC voltages over 500V.
Before calculating accuracy, study the associated specification notes carefully to see if any
derating factors apply.
dB = 20 log
V
IN
V
REF
---------------
dBm = 20 log
10.036mV
10V
------------------------- -59.96879dB=
dBm = 20 log
9.964mV
10V
---------------------- -60.03133dB=
A-10 Specifications

Keithley 2010 Specifications

General

Brand	Keithley
Model	2010
Category	Multimeter
Language	English