Is there any way to make this equation work on the HP 50g?
04-15-2018, 09:11 PM
Post: #1
 nathanpc Junior Member Posts: 2 Joined: Dec 2016
Is there any way to make this equation work on the HP 50g?
I'm writing a simple program in my 50g to be able to get the frequency response of a electronic low-pass filter. The equations are pretty simple to understand, so I decided to try and write a simple program and this is what I have come up with:

Code:
%%HP: T(0)A(D)F(.); \<<   100       @ Resistor value.   0.000001  @ Capacitor value.   -3        @ Cutoff point (dB).   0         @ Temporary value for "fn".   \-> r c fs fn   \<<     '-(1/(2*‡*f*c))*i' EVAL 'c' STO             @ Get capacitor complex impedance.     'fs=20*LOG(ABS(c)/ABS(r+c))' EVAL 'fn' STO  @ Frequency response function.     fn 'f' ISOL  @ Isolate f.     DUP          @ Create a backup.     EVAL         @ Should return the value of "f".   \>> \>>

The problem is that when I run it I get the following message "ISOL Error: Not reducible to a rational expression". I know this is because of the limitations of the solver in the HP 50g, but is there any way to make this work?
04-15-2018, 10:00 PM
Post: #2
 nathanpc Junior Member Posts: 2 Joined: Dec 2016
RE: Is there any way to make this equation work on the HP 50g?
I just tried something similar in my HP Prime and I was successful by running the same equation through the fsolve function like this:

Code:
fsolve(fs,f,0..30000)

And I was able to get the answer, 1587.77482493 in this case. Is there a equivalent solver function in the HP 50g where I can put a range of guesses?
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