Hi All Probably a very basic question. What are the units of the constants in transfer functions? It we take a look at the transfer function of a second order system we then have: H(s) = ω02/(s2+2ζω0s+ω02) ω0 is the natural resonance frequency and has a unit of rad/sec. ζ is the damping and has no unit. Hence everything ends up being without an unit if s also has the unit rad/sec. So for so good. If we now look at the transfer function for a first order response: H(s) = a/(s+a) where a = 1/τ, where τ is the time constant. The unit of τ is sec. Assuming again that the unit of s is rad/sec, a/(s+a) is not without a unit. When looking at more complex transfer functions the units become more confusion to me. I am most likely missing a small detail. However, I will be very grateful if someone can tell me what I am missing. Thanks.