Hello,

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');
```