Hi team,
I'm trying to measure the frequency in the range from 100 Hz to 11 KHz. But I need high accuracy in the range from 100 Hz to 200 Hz (± 4 Hz).
I made "Figure 2" circuit from the application note SNOA734B from TI, which adds a PNP transistor to acts as a cascade in order to improve nonlinearity. It works very well but in low frequencies I get an error of 10Hz and I need more accuracy.
Any idea of how to get less error without adding an active filter?
PS: the output range goes from 0 V to 5 V so when I introduce a 100 Hz signal instead of getting 50 mV I get 55 mV. The voltimeter has an accuracy of 5 uV with 6 1/2 digits so thats not the problem.
I'm trying to measure the frequency in the range from 100 Hz to 11 KHz. But I need high accuracy in the range from 100 Hz to 200 Hz (± 4 Hz).
I made "Figure 2" circuit from the application note SNOA734B from TI, which adds a PNP transistor to acts as a cascade in order to improve nonlinearity. It works very well but in low frequencies I get an error of 10Hz and I need more accuracy.
Any idea of how to get less error without adding an active filter?
PS: the output range goes from 0 V to 5 V so when I introduce a 100 Hz signal instead of getting 50 mV I get 55 mV. The voltimeter has an accuracy of 5 uV with 6 1/2 digits so thats not the problem.