I have an RS4D and I am trying to get the transfer function of the geophone (v6) using the document here
I am using the zeros and poles with a Matlab/Octave script to construct a transfer function. The gain is not specified so I tuned it to obtain the -3db @0.7 Hz as stated in the document. But when I plot the Bode diagram of the system I see that the amplitude at 44 Hz is -0.37 db instead of the -3db stated in the technical specification document.
What is the cause for this discrepancy? Am I missing something ?
Here is the code that I am using, you can run it on https://octave-online.net/ if you don’t have Matlab
zeros = [0 0 0]; poles = [-1 -3.03 -3.03 -666.67]; gain = 693; sys = zpk(zeros,poles,gain); [mag,phase,wout] = bode(sys); mag = mag(:); phase = phase(:); wout = wout(:); hzOut = wout/(2*pi); %rad/s => hz figure; plot(hzOut,20*log10(mag)); xlim([0 100]); ylim([-10 1]) grid on; xlabel('Hz'); ylabel('dB');