Calculating Output Amplitude Accuracy using dB

Some specifications, like the SDG800 and 1000 series, describe the vertical accuracy using dB

The SDG1000, for example, states:

Vertical Accuracy = ± (0.3 dB + 1 mV)

First, let’s convert the dB part…

Vertical Accuracy(dB) = 20 log (1 + (Error(%)/100))

±0.3 dB = 20 log (1 + (Error(%)/100))

Error (%) = 3.5%

So, if we set the voltage output to 1 V:

Vertical Accuracy = + (0.3 dB + 1 mV) = + ((1 V) * 3.5% + 1 mV) = + 0.036

So, for a 1 V set point, an in-tolerance sourced value would lie in the span of 1 +/- 0.036 V