Measurement Computing DBK Part 2 - Manual (Page 31)

DBK Option Cards and Module 899892 DBK43A & DBK43B, pg. 11
AC Coupling and Low-Pass Filter Options
Per channel, the strain gage modules each accommodate coupling and low-pass filter options including:
• AC-coupling or DC-coupling
• Using or bypassing the filter
• Choice of the filter’s corner frequency via a SIP resistor network
• Filter gain (default of ×2 can be changed to ×1).
Channel Header
0 JP103
1 JP203
2 JP303
3 JP403
4 JP503
5 JP603
6 JP703
The AC-coupling or DC-coupling choice on each channel is set by the presence or
absence of shunt jumpers on 2-pin headers. If the shunt jumper is in place, the
coupling is DC. If the shunt jumper is absent, the coupling is AC. See table for
channels and corresponding headers.
7 JP803
Channel Header
0 JP104
1 JP204
2 JP304
3 JP404
4 JP504
5 JP604
6 JP704
The choice of using or bypassing the low-pass filter for each channel is made by the
orientation of two shunt jumpers on a 2×2 pin header. When the shunt jumpers are
oriented horizontally (like the “bypass” symbol on the circuit board) the filter is
bypassed. When the shunt jumpers are oriented vertically (like the “filter” symbol),
the filter is in the signal path.
7 JP804
Channel Resistors
0 R105-R106-R107
1 R205-R206-R207
2 R305-R306-R307
3 R405-R406-R407
4 R505-R506-R507
5 R605-R606-R607
6 R705-R706-R707
The corner frequency of a low-pass filter is determined by three resistor
values in each filter circuit. The resistors are listed in the following table.
These resistor locations have been physically arranged to allow the use of a
6-pin SIP network as a convenient means of changing all 3 resistors. The
machined-pin socket will also allow you to insert individual resistors.
7 R805-R806-R807
Frequency Resistance ( Ω) Bourns P/N
133kHz 10 4606X-102-100
66.7kHz 20 4606X-102-200
26.6kHz 50 4606X-102-500
13.3kHz 100 4606X-102-101
6.67kHz 200 4606X-102-201
2.66kHz 500 4606X-102-501
1.33kHz 1K 4606X-102-102
667Hz 2K 4606X-102-202
266Hz 5K 4606X-102-502
133Hz 10K 4606X-102-103
66.7Hz 20K 4606X-102-203
26.6Hz 50K 4606X-102-503
The next table is a list of some common frequencies, the
nominal resistance value, and a Bourns part number for a
suitable network.
13.3Hz 100K 4606X-102-104
Channel R (10K)
0 R144
1 R244
2 R344
3 R444
4 R544
5 R644
6 R744
The active low-pass filters have a gain of ×2. This gain can be factored into the setup
calculations, or the filter gain can be changed to ×1. To change the gain to ×1 (unity)
for the corresponding channels, de-solder (or snip leads) and remove the resistors
shown in the table.
Note: The default ×2 gain option meets the needs of most applications.
7 R844