Driving apparatus for cross-coil type analog indicating instrument having reduced ripple

A driving apparatus for an analog instrument having a pointer that indicates a process quantity by deflecting through an angle in response to driven cross coils, said driving apparatus comprising:

• pulse signal generating means for generating a pulse signal at a frequency proportional to said process quantity;
• frequency-voltage conversion means connected tot he pulse signal generating means for generating an analog voltage proportional to the frequency of said pulse signal;
• and
• driving means connected to the frequency-voltage conversion means for driving said cross coils in accordance with said analog voltage;
• wherein said frequency-voltage conversion means comprises:
• voltage generating means connected to said pulse signal generating means for generating a ripple voltage proportional to the frequency of said pulse signal, said ripple voltage having ripple-voltage ripple;
• a hold means for generating the analog voltage;
• and
• voltage control means connected to said voltage generating means and to said hold circuit for controlling said controllable circuit so that the analog voltage tracks said ripple voltage with an amount of analog-voltage ripple less than said ripple-voltage ripple.