MOGlabs FSW4, Manual, Page: 29 / 72

5.2 PID parameters
23
Figure 5.2:
Interactive window for adjusting the PID constants, including
display of the instantaneous PID error value (in MHz) and the output value
(in Volts) for diagnostic purposes.
proximately the inverse of the frequeny response of the laser and
controller. For example, for a MOGL abs laser and DLC controller,
the laser frequency response is about 10 GHz per volt swing on
the
SWEEP
input, corresponding to a gain of 0
.
1 V
/
GHz. A neg-
ative gain can be used to invert the sign of the output voltage.
kp, ki, kd
Proportional, integral and differential coefficients, each limited to
a range of 0 to 1. Set
k
i
=
k
d
= 0 to use the analogue output as
a measure of laser wavelength, where
k
p
and the gain
G
define
the relationship between the output voltage and the measured
wavelength relative to the setpoint wavelength
λ
0
.
V
max
,
V
min
These set the upper and lower output voltage limits, and also the
integrator windup limits. See section below regarding windup.
V
offset
The offset voltage; that is, the output when the laser is at the
correct wavelength,
λ
=
λ
0
. For MOGL abs DLC controllers, set
v
offset
= 1
.
25.