This document serves as an application guide for Voltage-to-Frequency (V/F) converters. It addresses the problem of sending analog signals over long distances by converting them to frequency, which is less susceptible to interference during transmission via optical isolators or twisted-pair lines.
The text details two primary VFC architectures: the multivibrator type and the charge-balance type. It compares their advantages and disadvantages regarding accuracy, power requirements, and input impedance. Additionally, it covers error sources such as offset, gain, and linearity errors, providing specific procedures for trimming these parameters.
VFCs should use Teflon or polypropylene, or zero-temperature-coefficient (NPO, COG) ceramic capacitors to avoid dielectric absorption and ensure stability.
VFCs and sample-hold amplifiers should use Teflon, polypropylene, or zero-temperature-coefficient ceramic capacitors with low dielectric absorption.
Opto couplers require a high current drive of 10 to 30 mA to prevent linearity problems.