Measurement DBK48 User Manual

DBK48 Multipurpose Isolated Signal-Conditioning Module

Supports up to Sixteen 8B Modules

Description …… 1

Safety Concerns …… 2
Hardware Setup …… 2

Installing 8B Modules …… 4
Installing Plug-in Resistors to Create 4 to 20 mA Loops …… 5
Making Terminal Block Connections …… 6
Setting DBK48 Module Addresses …… 7
Configuring the Primary Data Acquisition Device …… 8
CE Compliance …… 9
Connecting the DBK48 to the Primary Data Acquisition Device …… 9
Using the DB25 Signal Output Connector …… 10
Powering the System …… 13

Software Setup …… 13
Specifications …… 16

Description

The DBK48 module can accommodate up to sixteen 8B isolated-input signal-conditioning modules for use
with Daq systems. A single cable connects the DBK48 output to the P1 analog input connector on the
primary device. One Daq system can support up to 16 DBK48 modules, providing a total of 256 isolated
analog input channels. The A/D converter scans the DBK48 channels at the same 5 µs/channel rate that it
scans all other channels from DBK series analog expansion and signal conditioning cards.

Other features of DBK48 include:

• Built-in power supply that operates from 10 to 30 VDC and can power a full complement of

8B modules (even with bridge excitation).

• Removable, plug-in screw-terminal blocks for convenient connection of 8B modules.

• On-board cold-junction sensing for thermocouple 8B modules.

• For each 8B module, 250 V isolation from the system and from other channels.

Note 1: Only channels 0, 2, 4, 6, 8, 10, 12, and 14 can be connected

to excitation. For example, in the above block diagram
Channel 0 could be connected to Excitation; Channel 1
could not.

Note 2: Each channel can accept a plug-in resistor to serve as a

8B Isolated Signal Conditioning Module 967792 DKB48, pg. 1

current shunt. In the above diagram, Channel 0 has a
current shunt installed, Channel 1 does not. Only current­input type modules require the plug-in resistors. The plug-in
resistors must be removed for all other module types.

Safety Concerns

DBK48 has a 250 VDC isolation specification. This is in a normal environment free of conductive
pollutants and condensation. The 250 VDC rating requires a proper earth ground connection to the chassis
and treatment of adjacent inputs as potentially hazardous.

Input cables must be rated for the isolation potential in use. Line voltage ratings are much lower than the
DC isolation values specified due to transients that occur on power lines. Never remove the cover unless all
inputs with potentially hazardous voltages are removed. The cover must be securely screwed on during
use.

Some things to remember:

WARNING

Shock Hazard! Voltages above 50 Vrms AC and voltages above 100 VDC are
considered hazardous. Safety precautions are required when 8B modules are used in
situations that require high-voltage isolation from the rest of the system. Failure to
practice electrical safety precautions could lead to injury or death.

• Properly tighten all chassis screws before system use.

• Never plug in or unplug potentially hazardous connections with power applied to any

connected equipment.

• Never attempt to change 8B modules or remove the cover plate while power is applied to

the DBK48. You could short out internally exposed circuits and cause personal injury or
equipment damage.

• Disconnect power, all equipment, and signal lines from the DBK48 prior to installing

8B modules.

Reference Note:

Refer to user manual that is associated with your primary Daq device.

DBK48, pg. 2 967792 8B Isolated Signal Conditioning Module

Hardware Setup

DBK48 Circuit Board Layout

8B Isolated Signal Conditioning Module 967792 DKB48, pg. 3

Installing 8B Modules

Electric shock hazard! Turn off power to the DBK48 and all connected modules and
devices before inserting or removing modules. Failure to do so could lead to injury or
death due to electric shock.

CAUTION

WARNING

Handle the 8B module carefully while inserting pins into the circuit board.
Do not over-tighten the mounting screw.

CAUTION

The discharge of static electricity can damage some electronic components.
Semiconductor devices are especially susceptible to ESD damage. You should always
handle components carefully, and you should never touch connector pins or circuit
components unless you are following ESD guidelines in an appropriate ESD
controlled area. Such guidelines include the use of properly grounded mats and wrist
straps, ESD bags and cartons, and related procedures.

If the DBK48 is not connected to a Daq device via the P1 connector, then remove the
Rnets from S01 and S02. These resistor networks connect each 8B module’s output to
the multiplexer for P1.

Up to sixteen 8B modules can be installed onto the DBK48 circuit board. The preceding figure indicates
module locations.

To install 8B modules:

1. Turn off power to the DBK48 and all

connected modules and devices.

2. Disconnect power, all equipment, and signal

lines from the DBK48 prior to installing 8B
modules. Be aware that isolated
measurements can present lethal voltages!

3. Remove the DBK48 top cover plate and set aside.

4. Align the 8B module’s retaining screw and pins

with the holes in the circuit board (see figure).

5. Gently press the module into place.

6. Tighten the retaining screw snug, but DO NOT OVERTIGHTEN.

7. Repeat steps 3, 4, and 5 for each additional module.

8. Return and secure the cover plate to the unit.

DBK48, pg. 4 967792 8B Isolated Signal Conditioning Module

Installing Plug-in Resistors to Create 4 to 20 mA Loops with 8B Voltage-Input Modules

Electric shock hazard! Turn off power to the DBK48 and all connected modules and
devices before inserting or removing resistors. Failure to do so could lead to injury or
death due to electric shock.

CAUTION

The discharge of static electricity can damage some electronic components.
Semiconductor devices are especially susceptible to ESD damage. You should always
handle components carefully, and you should never touch connector pins or circuit
components unless you are following ESD guidelines in an appropriate ESD
controlled area. Such guidelines include the use of properly grounded mats and wrist
straps, ESD bags and cartons, and related procedures.

Current Shunt
Resistors

WARNING

Shown with shunt resistors plugged-in for Channel 0 (at R0) and Channel 2 (at R2)

Location of Shunt Resistor Plug-In

Only voltage-input type modules require the plug-in shunt resistors. The plug-in resistors
must be removed for all other module types, including current-input type.

Inputs to monitor the commonly used 4 to 20mA current loops most often employ a 250Ω precision
resistor to develop a 1 to 5 VDC voltage drop.

Ideally, a resistor for such purpose should have a 0.1% tolerance (or better) with a minimum power rating
of 0.25W and a temperature coefficient of at least 25ppm/°C.

Lower values of resistance, for example, 62.5Ω [for a lower voltage drop within the loop of 0.25 to 1.25
VDC] will require that the host data acquisition device use a gain of x4 to maximize the signal resolution.

To create a 4 to 20mA current loop:

1. Turn off power to the DBK48 and all connected modules and devices.

2. Disconnect power, all equipment, and signal lines from the DBK48 prior to installing the

resistors. Be aware that isolated measurements can present lethal voltages!

3. Remove the DBK48 top cover plate and set aside.

4. Carefully plug the shunt resistor into the applicable plug-in location for the designated channel;

for example, R0 for Channel 0, R1 for Channel 1, R2 for Channel 2, etc. Repeat for each channel
as applicable.

DO NOT

Only voltage-input type modules require these resistors. The plug-in resistors
must be removed for all other module types, including current-input type.

solder the shunt resistors in place.

5. Reinstall the DBK48 top cover plate and secure in place.

8B Isolated Signal Conditioning Module 967792 DKB48, pg. 5

Making Terminal Block Connections

Input signals (and excitation when applicable) are wired to removable terminal blocks. Eight such blocks
can accept 2 channel inputs each. However, only channels 0, 2, 4, 6, 8, 10, 12, and 14 can be connected to
excitation. Thus the DBK48 is limited to 8 strain gages or 8 RTDs as only the even numbered channels
can be connected to excitation.

Each terminal block connects to a signal conditioning module within the DBK48. The blocks accept up to
14-gage wire into quick-connect screw terminals. Wiring schematics are provided below for RTDs,
thermocouples, 20 mA circuits, voltage (mV and V), and for full-bridge and half-bridge strain gages.

WARNING

Shock Hazard! The DBK48 is designed to sense signals that may carry dangerous
voltages. De-energize circuits connected to the DBK48 before changing the wiring or
configuration.

CH 0 is connected to a Full-Bridge Strain Gage.
CH 1 is shown not connected.

CH 0 is connected to a Half-Bridge Strain Gage.
CH 1 is connected for voltage input (mV or V).

CH 0 has a 3-wire connection to a potentiometer.
CH 1 is shown not connected.

CH 0 has a 3-wire connection to an RTD.
CH 1 is connected to a Thermocouple.

Only current-input type modules require the
plug-in resistors. The plug-in resistors must
be removed for all other module types.

CH 0 has a 2-wire connection to an RTD.
CH 1 is shown not connected.

CH 0 is shown not connected.
CH 1 is connected to a current shunt resistor
resulting in a 4 to 20 mA current loop.

DBK48, pg. 6 967792 8B Isolated Signal Conditioning Module