GW Instek GFG-3015 - Manual (Page 9)

GFG-3015 p.5
2. Product Introduction
The frequency feedback method applied by GFG-3015 is a new technique that
generates stable output frequency with extraordinary accuracy for Function
Generator.
The traditional function generators typically use integrating circuit and constant
current circuit techniques that are easily affected by operation temperature or the
quality of resistor or capacitor and other key components to occur poor frequency
accuracy. The innovative design for GFG-3015 is to get rid of these problems.
The frequency feedback system needs a compatible, powerful frequency counter.
GW has designed his own full-function counter chip, GFC-9701, for this system with
high frequency test range and full functions, including Period test, Duty test, Ratio
test, Time interval, Pulse wide, direct display and direct connect with CPU system.
GFG-3015 uses this Chip to read output frequency value at any time. Then CPU
will modify the correct value of D/A converter immediately according to this value, so
that the user can get a high accuracy frequency from GFG-3015 Function Generator.
Besides, the GFG-3015 can also generate a high accuracy frequency to provide
high frequency resolution.
Graph1 indicates the fundamental construction of a frequency feedback system.
Except the different design from the typical circuit, GFG-3015 system also has
micro controller (CPU unit) equipping an additional RS-232 interface functions which
will be used on any test system with other instrument or to be controlled by computer.
VCO
D/A
Convertor
CPU
Count er
(GFC-9701)
User
Interface
AMP O/P