Test and Measurement Forum

by **MarcWhitney** » Thu Jun 12, 2003 5:51 pm

What is the lower limit of THD (or THD+N) that can be measures with the 12 and with the 16 bit 'scope units?

What is the minium THD resloution that can be measured with the 12 and 16 bit units?

by **markspencer** » Fri Jun 13, 2003 8:48 am

Hi,

To caculate the values that you want you will need to use these equations:

[b]Total Harmonic Distortion ( THD)[\b]
Total Harmonic Distortion (THD) - the ratio of the harmonic power to the power at the datum. In the following equation, v1 is the RMS value at the datum frequency and v2..v5 are RMS values at the harmonics

THD = sqrt (v2^2 + v3^2 + v4^2 +v5^2....) / v1

[b]Total Harmonic Distortion + Noise ( THD+N)[\b]
Total Harmonic Distortion + Noise (THD+N) - the ratio of the harmonic power plus noise to the fundamental power. THD+N values will almost always be greater than the THD values for the same signal.

THD+N = sqrt (sum of squares of RMS values excluding datum)
/ (RMS value of datum)

Best regards,

Pico Technology

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