Table of Contents
Advertisement
DAC
The DAC or D-to-A converter converts a 16-bit number to an analog voltage. The input range of
the numbers is 65536 and the output voltage range is +/-10V or 20V. Therefore, the effective gain
of the DAC is
Digital Filter
The digital filter has three element in series: PID, low-pass and a notch filter. The transfer
function of the filter. The transfer function of the filter elements are:
The filter parameters, K, A, C and B are selected by the instructions KP, KD, KI and PL,
respectively. The relationship between the filter coefficients and the instructions are:
The PID and low-pass elements are equivalent to the continuous transfer function G(s).
where T is the sampling period.
For example, if the filter parameters of the DMC-1600 are
the digital filter coefficients are
DMC-1600
K= 20/65536 = 0.0003
PID
D(z) =
1 −
Low-pass
L(z) =
Z
Notch
N(z) =
(
⋅
K = (KP + KD)
4
A = KD/(KP + KD)
C = KI/2
B = PL
G(s) = (P + sD + I/s) ∗ a/(S+a)
P = 4KP
⋅
D = 4T
KD
I = KI/2T
a = 1/T ln (1/B)
KP = 4
KD = 36
KI = 2
PL = 0.75
T = 0.001 s
K = 160
A = 0.9
[V/count]
−
(
)
K Z
A
CZ
+
− 1
Z
Z
B
−
B
−
−
(
)(
)
Z
z Z
z
−
−
)(
)
Z
p Z
p
Chapter 10 Theory of Operation • 171
Advertisement
Table of Contents
