Measurement Computing WaveBook rev.3.0 - Manual (Page 40)

3-8 WBK14, WBK Expansion Options WaveBook User’s Manual
WBK12/13 - Programmable Low-Pass Filter Cards
Description
The WBK12 and WBK13 are 8-channel programmable low-pass filter cards for use with 1-MHz
WaveBook data acquisition system. These cards install directly into the WaveBook or WBK10/10H
expansion module and provide programmable low-pass filtering over all channels. Multiple WBK12 and
WBK13 cards can be installed in one system for up to 72 channels. All of the cards’ low-pass filters and
cutoff frequencies are configured via software. The WBK13 has the additional capability of simultaneous
sampling all channels. If multiple WBK13 cards are installed within one system, all channels are sampled
within 100 ns of each other.
Features of the WBK12 and WBK13 include:
• Low-Pass Filters. Each card provides 8 input channels, arranged in two 4-channel banks; the filter and
cutoff frequency configurations are applied per bank. The cards’ filters can be configured as either an
8-pole elliptic filter with cutoff frequencies of 400 Hz to 100 kHz, or an 8-pole linear-phase filter with
400 Hz to 50 kHz cutoff frequencies.
• Cutoff Frequencies. The WBK12 and WBK13 provide 747 discrete cutoff frequencies that can be
determined exactly by the formula Fc = 300 kHz/N; where the integer N = 3 to 750. Alternatively, you
can configure any channel to bypass the programmable filter entirely, resulting in a 1-pole low-pass
filter at about 500 kHz.
• Programmable-Gain Amplifiers. The cards’ programmable-gain instrumentation amplifiers can be
software selected to various gains on a per channel basis. The gains are set prior to the beginning of an
acquisition sequence and cannot be changed during an acquisition. Note that WBK12/13 gain
specifications are provided in Appendix A.
• Simultaneous Sample-and-Hold (SSH) (WBK13 only). In addition to the filtering capability of the
WBK12, the WBK13 also provides per channel SSH. Simultaneous sampling of all channels occurs at
the start of a scan sequence.
When using WaveBook with an SSH channel enabled, the per-channel sample rates are
reduced. The rate reduction is the same as that which would occur if another channel
were added. The per-channel rate (with SSH enabled) is:
1 MHz / (n+1), where n is the number of active channels.
Offset Adjust
Diff. Amp.
Sample/
Hold
(WBK13)
+
PGA
- S/H
Anti-Alias
LP Filter
Switched
Cap Filter
One of 8 Channels (Typical)
MUX
Buffer
Amplifier
SCI - Serial
Configuration
Interface
Dual
Divide-by-N
20 MHz
Clock
Octal
DAC
WBK12 & WBK13 Block Diagram
P10
mates
with
WaveBook
J10
P11
mates
with
WaveBook
J11
Hardware Setup
Configuration
The WBK12 and WBK13 configurations are controlled by software. No hardware settings are required.
Installation
WBK12 and WBK13 connect to WaveBook, or WBK10/10H the same way as the WBK11.
To install, use the same steps provided for the WBK11, on page 3-6.