Measurement DBK45 User Manual

DBK45 4-Channel SSH and Low-Pass Filter Card

Overview …… 1
Hardware Setup …… 2

Card Connection …… 2
Card Configuration …… 2
Configuring DBK45 Filter Sections …… 3
DaqBook/100 Series & /200 Series and DaqBoard [ISA type] Configuration …… 5
DaqBook/2000 Series and DaqBoard/2000 Series Configuration …… 5

Software Setup …… 5
DBK45 – Specifications …… 6

Reference Notes:

o Chapter 2 includes pinouts for P1, P2, P3, and P4. Refer to pinouts applicable to your

Overview

The DBK45 combines the features of the DBK17 (SSH) and the DBK18 (low-pass filter) cards. Each
DBK45 provides 4 input channels to a LogBook or Daq device system. Each of the main 16 analog input
channels can accept four DBK45s, for a maximum of 64 DBK45s and 256 analog input channels. The
simultaneous sample-hold function is activated at the beginning of each channel scan and freezes all
signals present on DBK45 inputs for the duration of the scan, allowing for non-skewed readings of all
channels.

system, as needed.

o In regard to calculating system power requirements, refer to DBK Basics located near

the front of this manual.

You should never set a DBK45 channel as the 1st channel in a scan due to timing of
the SSH line.

For each of the four channels, a separate filter and a sample-hold stage follow the input stage. The outputs
are connected to a 4-channel multiplexer stage. The enabled-output MUX allows four DBK45s to share a
common analog input channel.

The DBK45 has an instrumentation amplifier for each channel, with switch-selected gains of ×1, ×10,
×100, ×200 and ×500. A socket is provided for a gain resistor for custom gain-selection instead of the 5
factory-default gains. Gain for any channel can be set to any value between unity and ×500 by installing
an appropriate resistor. Four separate filter stages follow the 4 input stages. The outputs are connected to
a
4-channel multiplexer stage. The enabled output MUX allows four DBK45s to share a common analog
base channel.

Input can be connected to a channel’s BNC or terminal block connector. The differential inputs are
provided with switchable 100 kΩ bias resistors to analog common.

DBK Option Cards and Modules 987696 DBK45, pg. 1

Hardware Setup

Card Connection

DBK45 Block Diagram

DBK45 is equipped with a BNC connector for each of the four differential analog inputs. The card
includes terminal block connections, which can be used instead of the BNC connectors if desired.

Card Configuration

Factory Defaults:

Input Termination

DBK45 provides two 100 KΩ bias resistors for each analog input. For balanced 200 KΩ input
impedance, both resistors should be switched in. An 8-position DIP switch (SW5) can selectively engage
the bias resistors. The switches must be in the closed position to engage the termination resistors. For
unbalanced high input, only the (-) resistor should be used. If neither resistor is used, some external bias
current path is required. Examples of SW5 switch positions and the resulting impedance selection
follows.

CAUTION

Input voltage levels must not exceed ±5 V bipolar or 10 V unipolar.

• 100K bias resistors – Enabled

• Low pass filter – Disabled (bypassed)

• Gain – x1

• SSH - Enabled

Examples of Bias Resistor Selection Options

Gain Settings

On the printed circuit board, each channel has one gain-set switch. The switches are labeled GAIN 1,
GAIN 2, GAIN3, and GAIN 4. Each channel also has holes in the board for gain resistors labeled RG1 to
RG4. The 5 gain values for switch settings 0 to 4 are provided in the following figure. If a custom gain is
desired, the switch is set to position 0; and a gain resistor must be mounted and soldered onto the board.
The gain resistor’s value is determined by the formula: R

DBK45, pg. 2 987696 DBK Option Cards and Modules

= [40,000 / (Gain -1)] - 50 Ω

GAIN