1–2 Getting Started
1.1 General
The SIM960 is designed to maintain stability in systems requiring
low noise and wide bandwidth. The controller design consists of
a front end differential input amplifier, followed by an integrator
and a differentiator, arranged in what is known as the “ideal” PID
topology. The input amplifier (the “error amplifier”) differences the
the two single ended inputs, Setpoint and Measure, and multiplies
the resulting error signal (ε) by the proportional gain. The amplified
error is then passed to three parallel control paths:
1. The proportional path, no change is made to the signal.
2. The integral path with gain I.
3. The derivative path gain D.
These three signals can be independently selected to combine at a
summing amplifier, which is then buffered to the output. A constant
offset can also be added, which can be useful in applications that do
not use the Iterm. Mathematically, the behavior is
ε≡Setpoint −Measure (1.1)
Output =P×ε+Iεdt+Ddε
dt+Offset (1.2)
where the three terms within the braces, and Offset, can be indepen-
dently enabled or zeroed.
For internal stability, the actual differentiator is “rolled off” to limit
the derivative gain to +40 dB.
The output circuitry includes a soft limiter that turns on when the
output exceeds user specified upper and lower limits and clamps the
output to the limit level. The output bar display on the right side of
the front panel has red LEDs at each end to indicate when the output
is being limited.
1.2 Front Panel Operation
This section discusses the essentials of operating the SIM960 locally,
from the front panel. See Chapter 3 for remote operation.
•Press [Select] to choose which configuration parameter to view
in the numerical display. The indicator to the left of each
descriptor shows which parameter is displayed. When Shift
is highlighted, pressing [Select] steps the parameter selection
backwards.
SIM960 Analog PID Controller
