Rockwell-automation 1746-NI16V SLC 500 Analog Input Modules User Manua User Manual download pdf (Page 44)

Publication 1746-UM001A-US-P

4-8 Preliminary Operating Considerations

The hardware architecture has some bearing on how the module

firmware works and thus how a user can optimize performance when

fewer than all 16 channels are required. You can enable any number

of channels you want, but certain channel selections make data

available to your ladder program more quickly than others.

The module uses four A/D converters, each multiplexing four input

channels. The first A/D is for channels 0 through 3, the second for 4

through 7, and so forth. Although there is room in the configuration

data table to select a different filter for each channel, the filter value

programmed for the first channel of each A/D is used for all four

channels of that A/D. In other words, the filter selection made for

channel 0 is used for channels 0 through 3. The selection programmed

for channel 4 is applied to channels 4 through 7, and so forth.

If your application requires 12 or fewer of the 16 analog inputs, you

can achieve a module update time of about 3/4 of the time listed in

the table above for 16 channels if you enable channels in a certain

way. Use the first three channels on each A/D, leaving the fourth

channel disabled. For example, if you enable channels 0, 1, 2, 4, 5, 6,

8, 9, 10, 12, 13, and 14, your module update time is about 75 ms with

the 40 Hz filter instead of 100 ms listed in the table if all 16 inputs are

enabled.

Similarly, if you need 8 or fewer channels, you can achieve a module

update time of about one-half the 16-channel table values. For

example, if you enable only channels 0, 1, 4, 5, 8, 9, 12, 13, the

module update time is about 50 ms with a 40 Hz filter.

Finally, for very fast response you may use four or fewer channels.

This mode exploits the power of dedicating one A/D converter per

channel. The A/Ds are considerably faster when they do not have to

multiplex inputs.

NOTE

In this mode, the module provides four channels of

data every 4 ms, regardless of filter setting.

NOTE

The same channels are used on each of the four

A/D converters. In the 12-or-fewer-channels

example above, note that you are using channels 0,

1, and 2 on each of the four A/D converters, but

channel 3 on each remains disabled. If you just

enable the first 12 channels (0 to 11) on the module, and

leave channels 12 to 15 disabled, your update time is the

same as if you had enabled all 16 channels.

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 119 120

Comments to this Manuals

No comments

Rockwell-automation 1746-NI16V SLC 500 Analog Input Modules User Manua User Manual Page 44

Comments to this Manuals

Related products and manuals for Equipment Rockwell-automation 1746-NI16V SLC 500 Analog Input Modules User Manua