Horner APG SmartStix HE559MIX977 - Manual (Page 5)

MAN0561-02 27 FEB 2007 Page 5
All information subject to change without notice.
5
Channel Mode, Programmable Filter, and Output Default Configuration
The network supplies configuration information to the HE550MIX977 in the Consumed Directed Digital
Data Words sent to the HE550MIX977. In the first word, the low 12 bits, 1 through 12, are channel mode
bits. A low mode bit selects ±10V and a high mode bit selects ±20mA. The next three bits, 13 through
15, are input digital filter time constant codes and the high bit, 16, is an adaptive filter enable bit. In the
second word, the low 12 bits are channel scale bits. A low scale bit selects ±10V or ±20mA for the
corresponding channel. A high scale bit selects ±5V or 4-20mA. The upper four bits are unused.
Bit Channel
1 AI1
2 AI2
3 AI3
4 AI4
5 AI5
6 AI6
7 AI7
8 AI8
9 AQ1
10 AQ2
11 AQ3
12 AQ4
Each analog input on the HE550MIX977 has a single pole 345Hz (461uS) cutoff high frequency noise
filter. In addition a second digital filter may be specified in the first configuration word with the following
time constants.
Bit Time Constant
15 14 13
0 0 0 10 milliseconds (Nominal hardware scan rate)
0 0 1 15 milliseconds
0 1 0 35 milliseconds
0 1 1 75 milliseconds
1 0 0 155 milliseconds
1 0 1 315 milliseconds
1 1 0 635 milliseconds
1 1 1 1.275 seconds
This digital filter is useful for applications with significant amounts of random noise. The slower time
constants, while yielding better noise suppression, take a longer time to settle after step changes and are
also sensitive to impulse noise which is treated like Gaussian noise and averaged.
Bit 16 of the first configuration word may be set to specify an adaptive filter algorithm that:
1. Responds much more quickly to large step changes at slower time constants with full filtering of low
level noise.
2. Suppresses impulse noise at the expense of slightly slower response at the shortest time constant
settings. (Approximately 10 additional milliseconds)
Note that actual system response time is network dependent.