WBK16

Strain-Gage Module

Description ..................................................................................................... 1
Excitation Connection................................................................................... 6
Low-Pass Filter Customization .................................................................... 7
Configuration Diagrams................................................................................ 8Connecting to the DB9 Channel Input Connector ................................... 12
CA-177 Strain-Gage Cable ................................................................................. 12
CN-189, DB9 Adapter Option ............................................................................. 13

Using the WBK16/LC Load Cell Shunt Cal Option................................... 15
Using the CN-115-1 User-Configurable Plug-In Card Option.................. 19
Software Setup ............................................................................................ 22
Sensor Calibration....................................................................................... 22
The Five Methods of Sensor Calibration............................................................. 29
2 Point Manual Calibration .................................................................................. 30
2 Point Auto Calibration ...................................................................................... 30
Shunt (Internal Shunt) Calibration....................................................................... 31
External Shunt Calibration (2 Pt Shunt) .............................................................. 32
Name Plate Calibration ....................................................................................... 33

Changing Low-Pass Filter Displays .......................................................... 35
WBK16 – User Tips...................................................................................... 36
WBK16 – Specifications.............................................................................. 38

Description
The WBK16 is an 8-channel strain-gage signal-conditioning module for the WaveBook system. Up toeight of these modules (64 channels) can be accommodated by a WaveBook and scanned at 1 µs/channel.
Almost all bridge configurations are supported via a bridge-completion network and software. High-gain
differential-amplifier applications are also supported. Software controls bridge configuration, gain, offset,
excitation voltage, polarity, filtering, and the calibration process.
Refer to the following block diagram as needed while reading this section.

WBK16 Block Diagram
WBK16, Strain-Gage Module

949794

WBK16, pg. 1

Channel Selection
The eight independent channels are routed to the Channel Selection MUX (multiplexer) for output to the
WaveBook through the Analog Interface. The Digital Interface controls the channel-scanning process andallows digital configuration of all channels through the WaveBook's Serial Control Bus.

Excitation Source
Excitation power is programmable from a dual source—channels 1 to 4 from one source and channels 5 to
8 from another source. Each channel has a separate regulator with a fold-back current limiter. Up to 85 mA
is provided at 10 V out, decreasing to 30 mA when shorted. This is sufficient current to operate 120 Ω
gages at any voltage. Programmable output voltages of 0, 0.5, 1, 2, 5, and 10 volts are available. Remotesense inputs are provided and should be connected at the strain gage for best accuracy. If they are not used,
they need to be jumpered to the excitation output at the connector. The remote-sense inputs are fully
differential, and may even be connected across the completion resistor to form a constant-current linearized
quarter-bridge configuration.

Bridge Configuration
The strain gage is connected to the amplifiers through the Bridge Completion and Shunt Cal Network. This
network consists of user installed resistors for bridge completion. Several combinations of resistors andthree different shunt values may be installed simultaneously. External connector tie points and theprogrammable Input Configuration & Cal MUX determine the actual configuration in use. Once the
network is fully configured, most bridge configurations and resistances can be accommodated without reopening the box. The shunt resistors allow each bridge to be put into a known imbalance condition for
setting or verifying channel calibration. Shunt calibration allows a full-scale gain to be set without
physically loading the bridge.

Amplifiers
Each channel has an amplifier consisting of two series-connected stages. The instrumentation amplifier(PGIA) has programmable gains of x1, x10, x100, and x1000. A programmable gain amplifier (PGA)
follows, with a gain range of 1 to 20 in 28% steps. This results in a combined programmable gain rangeof 1 to 20,000 in 28% steps. The optimal gain is automatically determined during the gage calibration
process.

Offset Source
A low-drift, programmable offset voltage source with a range of ±3.0 V is used to balance the bridge
during the gage calibration process. This offset source will correct for mismatched bridge resistors andquiescent loads of the strain gage and still retain the full dynamic range.
Auto-zero removes the static portion of the strain load and zeros the input to compensate for any input
drift. Because this is done electronically, zeroing is independent of the user. Simply select the channels
that are to be auto-zeroed and the WBK16 will complete the task automatically.

Filters
Two different 4-pole Butterworth low-pass noise rejection filters are selectable through software by the
Output Selection MUX. The filters have a nominal cutoff frequency of 10 Hz and 1 kHz. Four SIP resistor
networks allow you to determine two cutoff frequencies. See the Hardware Configuration section for
details. If full bandwidth is required, a filter bypass mode is software selectable.

Output Selection
An AC coupling circuit with a 1-Hz cutoff frequency can be software selected by the MUX. This MUX
can also select an Inverting Amplifier for proper output signal polarity. The Inverter avoids having to
rewire the gage if the polarity is reversed. Note that the Inverter option is not available for AC-coupling
modes.

WBK16, pg. 2949794

WBK16, Strain-Gage Module

Front & Rear Panels
WBK16’s front panel has the following connectors and indicators as shown:
ACTIVE
READY
POWER

•
•

8 DB-9 connectors for bridge input
3 LEDs to indicate system status (Active, Ready, Power)

The rear panel has the power switch and the following connectors as shown:

•
•
•
•

Power

2 5-pin DIN5 connectors for power input and power pass-through1 DB-15M expansion control input connector
1 DB-15F expansion control output connector
2 BNC connectors for analog expansion in and out
ACPower
SourceAC
Power
Adapter+ 10 to 30 VDC
GND

WBK16 requires an input voltage between+V+10 and +30 VDC. The DC source should
be filtered but not necessarily regulated.
Power Input
The TR-40U AC power adapter isConnectors
recommended for AC line applications.
WBK16 Rear Panel
WBK16 may be powered with the suppliedPower
AC adapter that plugs into any standard AC
Switchwall outlet or from any isolated 10-30 VDC
source of at least 25 W (see figure). Before
WBK16 Power Connections
plugging unit in, make sure the powerswitch is in the “0” (OFF) position.
If you are using an AC power adapter, plug it into an AC outlet and attach the low voltage end to WBK16’s
DIN5 jack. If you are using another source of power, make sure leads are connected to the proper DIN5
terminals as shown in the figure.

CAUTION
Do not exceed the 5 amp maximum DC current limit of the POWER IN and POWER OUT
DIN connectors.
Internal DC to DC converters provide properly isolated and regulated +15V, +12V, and +5V from the single 10
to 30 VDC external source. Excitation power is derived from these internal converters. An internal replaceablefuse rated at 4 A provides overload protection. For replacement, use a
Littelfuse #251004. Reversed input polarity is the usual cause of a blown fuse.
Reference Note:
The WBK16 fuse (Littelfuse #251004, rated at 4A) is located on the board, between thePower Switch and the Power In connector.

Reference Note:
For details on powering WaveBook systems, refer to the WaveBook manual chapter entitled
System Setup and Power Options.

WBK16, Strain-Gage Module

949794

WBK16, pg. 3

Stacking Modules
For convenient mounting, the WBK16 has the same footprint as other WBK modules and WaveBooks.
Corner brackets (protective ears) provide a means for stacking WaveBooks and modules. Screw-on
handles are available for portable applications.
When using WBK17 modules in conjunction with other WBK modules, the WBK17
modules must be located closest to the WaveBook/516 (or /516A), due to the CA-217
cable length. The order of the other WBK modules does not matter.

Board Layout
The following figure shows the WBK16 board layout for locating user-accessible components. You may
need to refer to this figure to locate components referenced in the text. The jumper positions are not userfunctions, and are only shown for reference in case they are dislodged.

WBK16 Board Layout
Configuration options on WBK16 include:• Customization of low-pass filter frequencies using resistor networks• Bridge completion resistor installation• Shunt calibration resistor installation

CAUTIONBe careful to avoid component damage while WBK16 enclosure is open. Always
remove bridge completion headers (CN-115) from the unit before soldering resistors
in the headers.

WBK16, pg. 4949794

WBK16, Strain-Gage Module

A fan draws and exhausts air through vents in the WBK16 enclosure. To maintainsufficient cooling it is important to keep the fan and vents free of obstruction.

Bridge Applications
WBK16 can accommodate many different strain-gage configurations. All strain-gage bridge configurations
consist of a 4-element network of resistors. The quarter, half or full designation of a strain gage refers to
how many elements in the bridge are strain-variable. A quarter-bridge has 1 strain-variable element; a halfbridge has 2 strain-variable elements; and a full-bridge has 4 strain-variable elements.
Full-bridges generally have the highest output and best performance. Output signal polarity is determinedby whether the strain-variable resistance increases or decreases with load, where it is located in the bridge,
and how the amplifier inputs connect to it. Configuration polarity is not important in WBK16, due to aninternal software-selected inversion stage. This simplifies bridge configuration.
Each WBK16 channel has locations for five bridge-completion resistors. These BCR’s are for use withquarter and half-bridge strain gages. The resistors make up the fixed values necessary to complete the4-element bridge design.
A full-bridge gage requires no internal completion resistors, but they may still be installed for otherconfigurations in use. The additional resistors will be ignored when the software has selected full-bridge
mode. Both quarter- and half-bridge gages require an internal half-bridge consisting of header positions Rg
and Rh. The recommended minimum values are 0.1%, <5 PPM/°C drift, 1 KΩ, and 0.25-watt resistors.
Lower values will dissipate more power and add heat. Values >1KΩ will increase the amount of drift andnoise. The same value half-bridge resistors can be used for any resistance strain gage. This internal halfbridge will be automatically selected by the software when needed.
Internal 1 MΩ shunt resistors are used to avoid open circuits.
These resistors are not suitable for high-accuracy/low-noise applications.

A quarter-bridge gage additionally requires a resistor of equalvalue to itself. Up to 3 different values may be installed
simultaneously in header positions Ra, Rc, Re. All of these
resistors are connected to the (-) excitation terminal. An external
jumper at the input connector determines which resistor isutilized. Therefore, 3 different quarter-bridge values can besupported without opening the enclosure. Each different value
bridge would simply have the jumper in a different location;
when the gage is plugged in, the proper resistor is then alreadyselected. Configurations with the completion resistor on the (+)
excitation are redundant, due to the internal inversion stage, andnot used.

The bridge-configuration figures in the following text show various strain-gage configurations divided into
4 groups: Full-bridge, half-bridge, quarter-bridge, and high-gain voltmeter. Many of these configurations
can coexist but are shown individually for clarity.

WBK16, Strain-Gage Module

949794

WBK16, pg. 5

Excitation Connection
Remote sense inputs are provided for the excitation regulators. The excitation voltage will be most accurate
at points where remote sense lines are connected, preferably at the bridge (this is often referred to as a
6-wire connection). Long cables will reduce the voltage at the bridge, due to current flow and wire
resistance, if remote sense is not used.
If the 6-wire approach is not used, the remote sense inputs must be jumpered to the excitation
outputs at the input connector. Internal 1 MΩ resistors are also connected where the jumpers would belocated to prevent circuit discontinuities. These 1 MΩ resistors are not suitable for high-accuracy
excitation-voltage regulation.
3-wire quarter-bridge configurations do not benefit from external remote sense connections. The leadresistance is actually a balanced part of the bridge. If the + remote sense input is connected to the + input
on a quarter-bridge, the voltage is regulated across the bridge completion resistor. This results in aconstant-current linearized quarter-bridge; otherwise quarter-bridges are not perfectly linear.
Shunt-Calibration Resistors. StrainBooks and WBK16s each provide three physical locations for internal
shunt-calibration resistors for each channel. Each shunt resistor is switched in from the EXCITATION (-)
to the IN (+) of the Instrumentation Amp by a FET switch to create a repeatable bridge imbalance. Internal
resistance of the circuit is about 1 kΩ; the exact amount is automatically accounted for in the software. The
software also allows selection of the three shunt resistors ( B, D, F ). An internal inversion stage insurescorrect polarity during the shunt calibration process; which arm is shunted is therefore irrelevant. Header
positions Rb, Rd, Rf correspond to the software shunt resistor selections of B, D, F.
For any balanced bridge, a resistance value can be placed in parallel with one element to create apredictable imbalance and output voltage. This shunt-resistance value can be calculated by the following
equation, where Vout is the differential output voltage of the gage.
Example:RShunt = RBridge Arm [ ( VExcitation / 4 (Vout)) - 0.5 ]RShunt = 350 [ ( 10 / 4(0.020)) - 0.5 ] = 43,575Ω

CAUTIONBe careful to avoid component damage while the WBK16 enclosure is open. Always
remove bridge completion headers (adapter plugs) from the unit before soldering
resistors in the headers.

Configuring the Bridge Completion Resistor Modules. For each channel, theboard has a 2×8 resistor socket with rows designated A through H. The removable
adapter plugs are included for soldering in the resistors. Additional adapter plugs
are available for convenient changeover of alternate configurations. Resistor Ra is
located nearest the front panel.
oooHalf-bridge completion resistors consist of Rg and Rh.
Quarter-bridge completion resistors consist of Ra, Rc, and Re.
Shunt resistors consist of Rb, Rd, and Rf.

Inserting resistors directly into the socket makes an unreliable connection andis not recommended. Remove the plug from the main board; then solder
resistors to the adapter plug as indicated. To avoid damaging the pinalignment on the plug, solder with minimal heat. After soldering, the resistor
leads should be snipped off close to the support.

WBK16, pg. 6

Solder resistor lead
into support fork.

949794

Soldering Resistors to
Adapter PlugWBK16, Strain-Gage ModuleReference Notes:
Schematics of various bridge configurations begin on page 8.
DB9 connector information, including use of the optional CN-189 adapter, is locatedon page 12.
The WBK16/LC Load Cell Shunt Cal Internal Option is discussed on page 15.
The CN-115-1 User-Configurable Plug-In Card performs the same function as theCN-115 Header Plug-in Option. CN-115-1 is discussed on page 19.

Low-Pass Filter Customization
Each StrainBook and WBK16 module has 68 kΩ 4-resistor SIP networks installed at the factory. These
networks result in a 10.9 Hz cutoff for filter A and a 1092 Hz cutoff for filter B. The 4-resistor SIP
networks are socketed and can be altered to the range of values in the table below. Individual resistors may
also be used but should be matched within 2%. Cutoff frequency accuracy is about ±5%.
If you change the filter nominal values, be sure to update the filter cutoff frequencies in
the WaveView software. This is discussed in the Chapter 4 section entitled Changing
Low-Pass Filter Displays.

Filter A

Filter B

Resistancein kΩFrequency
in Hz

Resistancein kΩFrequency
in Hz

Resistancein kΩFrequency
in Hz

Resistancein kΩFrequency
in Hz

470
330
220
150
100
82
68
47

1.58
2.25
3.38
4.95
7.43
9.05
10.9
15.8

33
22
15
10
8.2
6.8
4.7
3.3

22.5
33.8
49.5
74.3
90.5
109
158
225

470
330
220
150
100
82
68
47

158
225
338
495
743
905
1092
1580

33
22
15
10
8.2
6.8
4.7
3.3

2250
3375
4950
7425
9055
10919
15798
22500

Lower frequency filters, such as the 10-Hz filter provided, are generally used to reduce higher frequency
noise. Some common sources of noise are: 50/60 Hz power line pickup on long cables, electromagnetic
interference (EMI) from nearby equipment, unwanted vibrations in the strain gage system itself, or at
higher gains the intrinsic thermal noise of the amplifiers. All information above the cutoff will also be lost
due to the filter’s function.
The 1-kHz filter provided is typically used as an anti-aliasing filter, or for slight noise reduction while still
maintaining moderate bandwidth.

WBK16, Strain-Gage Module

949794

WBK16, pg. 7

Configuration Diagrams
Full-Bridge Configurations
The full-bridge has four strain-variable elements and requires no bridge completion components. Quarter andhalf-bridge resistors may be left installed. Any bridge resistance from 60 to 1000 ohms can be accommodated.

RH+Sense+Excitation

3

5

JN01 2

4

1

9
8

3

IA

7

2
6

RG

RF

RE

RD

RC

DB-9
Input

RA

External
BridgeRB

1
Switches
accessedthroughsoftware-Excitation-SenseInternal Bridge Completion

Full-Bridge (+), Any Resistance from 60 to 1000 Ohms

In this connection, excitation voltage isregulated at the connector. Thisconfiguration should only be used forshort cable lengths. Output polarity may
be altered by interchanging the (+) and (-)
input or by selecting the software invert
function.

RH+Sense+Excitation

3

5

JN01 2

4

1

9
8

3

IA

7

2

In this connection, excitation voltage isregulated at the strain gage.

6

RG

RF

RE

RD

RB

DB-9
Input

RA

External
BridgeRC

1
Switches
accessedthroughsoftware-Excitation-SenseInternal Bridge Completion

This eliminates errors due to cable
losses and is the preferred connection
for longer cables.

Full-Bridge (+), with Remote Sense

RH+Sense+Excitation

3

5

JN01 2

4

1

9

8
3

IA

7
2

6

RG

RF

RE

RD

RB

DB-9
Input
RA

External
BridgeRC

1
Switches
accessedthroughsoftware

Internal Bridge Completion

Full-Bridge (+), with B, D, or F Shunt

WBK16, pg. 8949794-Excitation-SenseThe B, D, or F shunt resistor may be
software selected when installed asshown. Output polarity during shuntcalibration will be automaticallycorrected by software. The shunt resistor
value will typically be different for eachvalue of bridge resistance.

WBK16, Strain-Gage Module

Half-Bridge Configurations
The half-bridge has two strain-variable elements and requires two internal bridge completion resistors (BCRs).
Any bridge resistance from 60 to 1000 ohms can be accommodated for either the internal or external bridge.

RH+Sense+Excitation

3

5

JN01 2

4

1

9

8
3

IA

H BCR
G BCR
F Shunt
E
D Shunt
C
B Shunt
A

7
2

In this connection, excitation voltage isregulated at the connector.

6

RG

RF

RE

RD

RB

DB-9
Input
RA

External
BridgeRC

1
Switches
accessedthroughsoftwareThis configuration should only be used
for short cable lengths.

-Excitation-SenseInternal Bridge Completion

Half-Bridge (+), Any Resistance from 60 to 1000 Ohms,
B,D, or F Shunt

Output polarity can be altered by
selecting the software invert function.
The B, D, or F shunt resistor may be
software selected. Output polarity during
shunt calibration will be automaticallycorrected by software.

RH+Sense+Excitation

3

5

JN01 2

4

1

9
8

3

IA

7

2

In this connection, excitation voltage isregulated at the strain gage.

6

RG

RF

RE

RD

RC

DB-9
Input

RA

External
BridgeRB

1
Switches
accessedthroughsoftwareThis is the preferred connection for
longer cables.

-Excitation-SenseInternal Bridge Completion

Half-Bridge (+), with Remote Sense

RH+Sense+Excitation

3

5

JN01 2

4

1

9

8
3

IA

7
2

6

RG

RF

RE

RD

RB

DB-9
Input
RA

External
BridgeRC

1Internal Bridge Completion

Switches
accessedthroughsoftware-Excitation-Sense3-Wire TC Half-Bridge, Software Invert & B, D, F Shunt Available

WBK16, Strain-Gage Module

949794This occasionally utilized connection canbe made as shown. Two resistors
normally reserved for quarter-bridge
completion must be used.
For compatibility with otherconfigurations, use of one of the above
two configurations is preferred overthis one.

WBK16, pg. 9

Three-Wire Quarter-Bridge Configurations
The three-wire quarter-bridge has only one strain-variable element and requires three bridge completion resistors(BCRs). The internal half-bridge may be any two matched values, but the remaining resistor must match theexternal quarter-bridge value precisely. Three of these values may be installed simultaneously when connected
as shown below; the connector pins determine which resistor is used. With all three values installed, WBK16
can accommodate all three quarter-bridge values without changing the internal resistors.

RH+Sense+Excitation

3

5

JN01 2

4

1

9

8
3

IA

7
2

A 120-ohm resistor and its corresponding
shunt value may be installed as shown.

6

RG

RF

RE

RD

RC

DB-9
Input

RA

External
BridgeRB

1Internal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseThree-Wire Quarter-Bridge (+),
Using RA (120-Ohm nominal), B Shunt Resistor

RH+Sense+Excitation

3

5

JN01 2

4

1

9
8

3

IA

7

2

A 350-ohm resistor and its corresponding
shunt value may be installed as shown.

6

RG

RF

RE

RD

RC

DB-9
Input

RA

External
BridgeRB

1Internal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseThree-Wire Quarter-Bridge (+),
Using RC (350-Ohm nominal), D Shunt Resistor

RH+Sense+Excitation

3

5

JN01 2

4

1

9

8
3

IA

7
2

6

RF

RE

RD

RC

RB

DB-9
Input

RA

External
BridgeRG

1Internal Bridge Completion

Switches
accessedthroughsoftware

A 1000-ohm (or other value) resistor andits corresponding shunt value may beinstalled as shown.

-Excitation-SenseThree-Wire Quarter-Bridge (+),
Using RE (1-KOhm nominal), F Shunt Resistor

WBK16, pg. 10949794

WBK16, Strain-Gage Module

High-Gain Amplifier Configurations
WBK16s are useful as a programmable high-gain amplifier. No external bridge is used in these cases.
The inputs are fully differential.
Note: The differential inputs are not isolated inputs. Common mode voltage should not exceed ±10 V.

RH+Sense+Excitation

3

5

JN01 2

4

1

9
+

8

3

-

IA

7

2

No pull-down resistors are required if the
input signal ground is connected to Pin 1
as shown.

6

RG

RF

RE

RD

RB

DB-9
Input
RA

External
BridgeRC

1Internal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseUniversal High-Gain Amplifier Input, Differential

RH+Sense+Excitation

3

5

JN01 2

4

1

9
+

8

3

-

IA

7

2
6

RG

RF

RE

RD

RB

RA

DB-9
Input

RC

1
External
BridgeInternal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseUniversal High-Gain Amplifier Input, Differential with Pull Downs

A floating input without a groundreference, such as a battery, requires apath for input bias currents. Pull-downresistors of 1k to 10MΩ may be installed
as shown to provide this function.
A 10MΩ resistor would be suitable inmost cases.
These resistors are not compatible withother bridge configurations.

RH+Sense+Excitation

3

5

JN01 2

4

1

9

+

8
3

IA

7
2

6

RG

RF

RE

RD

RB

DB-9
Input

RA

External
BridgeRC

1Internal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseIf the (-) input is ground referenced, theinput is non-differential and pull-downresistors are not required. A floating
source would still result in a truly
differential input.

Universal High-Gain Amplifier Input, Single-Ended

WBK16, Strain-Gage Module

949794

WBK16, pg. 11

Connecting to the DB9 Channel Input Connector
CAUTION
Remove the module from power and disconnect the unit from all externallyconnected equipment prior to connecting cables, signal lines, and/or removing thecover to install or remove components. Electric shock or damage to equipment can
result even under low-voltage conditions.
Take ESD precautions (packaging, proper handling, grounded wrist strap, etc.)
Use care to avoid touching board surfaces and onboard components. Only handle
boards by their edges (or ORBs, if applicable). Ensure boards do not come into
contact with foreign elements such as oils, water, and industrial particulate.
The figure shows the pinout of the DB-9 connector used for channels 1
through 8 located on the front panel. The strain gage will connect
directly to these pin sockets, unless the CN-189, DB9 Adapter option isused. The CN-189 option is discussed in the following sub-section.
WBK16’s DB9 Pinout
A quality cable (such as the CA-177 strain-gage cable) can improve performance of the system, especiallywith long cable runs. Use cable with an overall shield connected to the DB9 metal shell. Twisted pair cablewith paired leads for signal input, excitation output, and remote sense input is also beneficial.
The wires should be soldered to the DB9 to eliminate noise created by contact resistance variations. The
protective hoods should be installed over the 9-pin connectors during use to avoid draft-induced thermalelectric noise in the connector solder joints. Molded cables wider than 1.23 inches will not fit WBK16's
connector spacing.

CA-177 Strain-Gage Cable
Use cable with an overall shield connected to the DB9 metal shell. Twisted pair cable with paired leads for
signal input, excitation output, and remote sense input are also beneficial.
The wires should be soldered to the cable’s DB9 connector to eliminate noise created by contact resistancevariations. The protective hoods should be installed over the 9-pin connectors
during use to avoid draft-induced thermal-electric noise in the connector solder
joints.
Molded cables wider than 1.23 inches will not fit the DB9 connectors due toavailable space between the unit’s connectors.
CA-177 Strain-Gage Cable Pinout*
DB9 Male End (P1)
Pin 1
Pin 2
Pin 3
Pin 4
Pin 5
Pin 6
Pin 7
Pin 8
Pin 9
Shell

Cable Pinout*

Cable CA-177 Specifications

Unterminated End (P2)
Brown wire
Red wire
Orange wire
Yellow wire
Green wireBlue wire
Purple wire
Black wire
White wire
Drain wire---

P1 Cable End: DB9 male, assembled metal
hood with thumbscrews(solder cup DB9).
P2 Cable End: Unterminated, blunt cut.
Cable Type: Belden 9614 or equivalent.
Wire Gauge: 24 AWG.
Outer Shield: Foil and 65% braid.
Number of Conductors: Nine (9) plus drain.
Dimensions: Length: 72" ± 4",
Connector width: 1.220" maximum
P1-to-P2 Pinout Specifications:
As indicated at left.

*Cable DB9 numbering is opposite of that found on the WBK16 to allow for correct pin mating.

WBK16, pg. 12

949794

WBK16, Strain-Gage ModuleCN-189, DB9 Adapter Option
CAUTION
Remove the WBK16 from power and disconnect the unit from all externallyconnected equipment prior to connecting cables, signal lines, and/or removing thecover to install or remove components. Electric shock or damage to equipment can
result even under low-voltage conditions.
Take ESD precautions (packaging, proper handling, grounded wrist strap, etc.)
Use care to avoid touching board surfaces and onboard components. Only handle
boards by their edges (or ORBs, if applicable). Ensure boards do not come into
contact with foreign elements such as oils, water, and industrial particulate.
Be careful to avoid component damage while the WBK16 module is open. Always
remove bridge completion headers (CN-115) from the unit before soldering resistors
in the headers.
The CN-189 option consists of two 7-pad jumpers (P3 and P4), a DB9 connector, and a 9-slot screwterminal block. The adapter plugs into channel input DB9 connectors on StrainBooks and WBK16
expansion modules.
With use of the terminal block and appropriate shorting of jumper pads, the user can easily set up thedesired bridge configuration. A table indicating bridge types and the respective CN-189 jumper pad shorts
follows shortly. In some cases, the user may want to install a resistor at location R1. The electrical
relation of CN-189 components is shown in the following schematic.

CN-189 DB-9 Adapter Option
The CN-189 is intended for convenience and is not shielded. Higher signal quality will
be obtained with the use of shielded cables, such as the CA-177 strain gage cable.

WBK16, Strain-Gage Module

949794

WBK16, pg. 13

CN-189 Schematic

CN-189 DB9 Adapter for WBK16, Configuration Table

1
2
3
4
5
6
7
8
9
10
11

Function

P3

P4Internal Excitation Sense¼ Bridge Using (RA) 2-Wire¼ Bridge Using (RC) 2-Wire¼ Bridge Using (RE) 2-WireHigh Gain Amp Ground Path (Short)High Gain Amp (Resistive) Ground Path
(EXT)High Gain Amp (RE) Ground Path (INT)High Gain Amp (RC) Ground Path (INT)High Gain Amp (RA) Ground Path (INT)
Current Measurement (Differential)
Differential Load Resistor

Short 1 and 2
Short 3 and 4
Short 5 and 6
Short 6 and 7

Short 6 and 7

Resistor Used in R1

Short 5 and 6
Resistor between
5 and 6
Short 1 and 2
Short 2 and 3
Short 4 and 5
Shunt resistor in R1
Load resistor in R1

For the functions listed in the preceding table, internal WBK16 configurations
still apply as indicated on pages 8 through 12 .

WBK16, pg. 14

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WBK16, Strain-Gage Module

Using the WBK16/LC Load Cell Shunt Cal Option
Purpose of the WBK16/LC
The WBK16/LC provides a non-committed dry contact on two pins of a single StrainBook or WBK16
channel connector. The WBK16/LC can be used for virtually all single value shunt calibration
requirements, some of which are not possible with the internal FET/analog switch provisions in thestandard channel configurations.

WBK16/LC
Shunt calibrations of load cells and pressure transducers, while conceptually equivalent to shunt calibrationof strain gages, do exhibit a few differences.
oooVarying physical locations of the shunt cal resistor
The shunt resistors are often expressed in engineering
units instead of ohms
A shunt switch contact with nominallyzero-ohms is required

Any of the following situations can be accommodated by the uncommitted shunt contact of the
WBK16/LC:•A shunt calibration resistor may be provided internal to a load cell or transducer, with an extra
connector pin or additional wire in the cable with the requirement that the line be connected to oneof the excitation lines to produce a signal equivalent to a specific physical stimulus applied to thetransducer.

•

A shunt calibration resistor with a defined physical equivalence may be supplied with a transducer
giving specific instructions for connections to provide a signal output from the device.

•

A user may, empirically, or by electrical calculation, determine the physical equivalence of anavailable resistance connected to accessible transducer lines to produce an output signal.

The shunt calibration resistor can be located internal (soldered onto the WBK16/LC in the provided “R1”location) or external to the host StrainBook or WBK16 at a wiring transition location. Four schematics
which include an External Full Bridge follow.

WBK16, Strain-Gage Module

949794

WBK16, pg. 15

CAUTION
Make the DB9 pin # 2 connection to the “low-side” or the “high-side” of thecircuit. BUT NEVER TO BOTH! Doing so will create a short circuit that could
damage equipment.
Internal Shunt Resistor, Low-Side Connection

Full Bridge (+) with Internal Shunt Resistor Installed at R1 on the WBK16/LC
DB9 Pin 2 Connected to the Low-SideInternal Shunt Resistor, High-Side Connection

Full Bridge (+) with Internal Shunt Resistor Installed at R1 on the WBK16/LC
DB9 Pin 2 Connected to the High-Side

CAUTION
Make the DB9 pin # 2 connection to the “low-side” or the “high-side” of thecircuit. BUT NEVER TO BOTH! Doing so will create a short circuit that could
damage equipment.
Note 1: The switches represented in the schematics are controlled by software.

WBK16, pg. 16

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WBK16, Strain-Gage Module

CAUTION
Make the DB9 pin # 2 connection to the “low-side” or the “high-side” of thecircuit. BUT NEVER TO BOTH! Doing so will create a short circuit that could
damage equipment.
External Shunt Resistor, Low-Side Connection

Full Bridge (+) with External Shunt Resistor
DB9 Pin 2 Connected to the Low-SideExternal Shunt Resistor, High-Side Connection

Full Bridge (+) with External Shunt Resistor
DB9 Pin 2 Connected to the High-Side

CAUTION
Make the DB9 pin # 2 connection to the “low-side” or the “high-side” of thecircuit. BUT NEVER TO BOTH! Doing so will create a short circuit that could
damage equipment.
Note 1: The switches represented in the schematics are controlled by software.
WBK16, Strain-Gage Module

949794

WBK16, pg. 17

Caveats
Transducers and load cells, most often employ full bridges with four active strain gages to benefit frominherent temperature compensation and maximum output signal levels.
The mV/V sensitivities vary from unit to unit, but series resistors may be placed in the excitation lines toadjust them into a particular range window. This technique makes externally connected shunt calibration alittle less exacting if the shunt resistor is not connected directly across the desired bridge arm. A shuntcalibration resistor provided internally by the transducer manufacturer will usually require connection to an
externally accessible node to activate the shunt. The variations in connection requirements require theflexibility of a non-committed dry contact as provided by the WBK16/LC module.
Shunt calibration generally is done by shunting one arm of a bridge with four active arms. For this reason,
it is recommended that simulated signal levels be limited to about 20% of the full-scale output of thetransducer. Attempting to achieve a high level output with a single resistor will introduce non-linearity
errors into the picture. For example, a 5000 pound load cell should be shunt calibrated with a resistancethat will introduce about a 1000 pound output signal. Attempting to produce a 4000 pound signal byshunting one of the bridge legs will generally not produce the same quality result.

Installation
CAUTION
Remove the WBK16 module from power and disconnect the unit from all externallyconnected equipment prior to connecting cables, signal lines, and/or removing thecover to install or remove components. Electric shock or damage to equipment can
result even under low-voltage conditions.
Take ESD precautions (packaging, proper handling, grounded wrist strap, etc.)
Use care to avoid touching board surfaces and onboard components. Only handle
boards by their edges (or ORBs, if applicable). Ensure boards do not come into
contact with foreign elements such as oils, water, and industrial particulate.
Be careful to avoid component damage while the WBK16 is open. Always remove the
WBK16/LC from the unit before soldering resistors.

You can easily install a WBK16/LC as follows:
Note:

If a shunt calibration resistor is to be mounted on the WBK16/LC it should be done prior to theinstalling the WBK16/LC. Shunt calibration resistors should be soldered in location R1 on the
WBK16/LC.
1.
2.
3.
4.
5.
6.

7.
8.
9.
WBK16, pg. 18

Review the preceding CAUTIONS.
Remove the StrainBook [or WBK16] from power and disconnect the unit from all external
devices and signals.
Observe proper ESD precautions.
Remove the cover from the StrainBook [or WBK16].
Locate the CN-115 channel header(s) in which the
WBK16/LC modules are to be installed.
Remove one shunt jumper from each of the two
3-pin headers. The 3-pin headers are located beside
the CN-115 16-pin header sockets (see figure).
Remove the CN-115-1 (or CN-115) to expose theheader socket.
Carefully plug the module into the header socket.
CN-115 Headers for CH1 and CH2
Re-install the cover to the StrainBook [or WBK16].

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WBK16, Strain-Gage Module

Calibration Using WaveView
Reference Note:
The Calibration Parameters Tab Selected section of Chapter 4 includes screen shots
and text related to the following steps.
1.
2.
3.
4.

5.
6.

7.

Select ‘load cell’ or ‘transducer’ from the pull-down ‘Sensor Type’ menu.
Select ‘shunt’ from the pull-down ‘Calibration Method’ menu.
Enter a maximum intended value in the ‘Maximum Applied Load’ cell in engineering units.
Enter a value slightly below zero engineering units in the Quiescent/Tare cell in engineering
units. [Note: if the transducer must measure bi-directionally, for example, pressure andvacuum, enter the maximum anticipated negative engineering units.]
Enter the physical equivalence in engineering units in the ‘Point 2’ cell of the shunt calibration
resistance.
This method assumes the 0.00 engineering units already in the ‘Point 1’ cell is the intended
physical equivalence of the non-shunted transducer or load cell. [Possible exceptions areatmospheric pressure transducers and load cells installed under load in which the relativechange is not the measurement of interest.]
Push the channel calibrate button and wait for the window verifying successful calibration.

Using the CN-115-1 User-Configurable Plug-In Card Option
CAUTION
Remove the WBK16 module from power and disconnect the unit from all externallyconnected equipment prior to connecting cables, signal lines, and/or removing thecover to install or remove components. Electric shock or damage to equipment can
result even under low-voltage conditions.
Take ESD precautions (packaging, proper handling, grounded wrist strap, etc.)
Use care to avoid touching board surfaces and onboard components. Only handle
boards by their edges (or ORBs, if applicable). Ensure boards do not come into
contact with foreign elements such as oils, water, and industrial particulate.
Be careful to avoid component damage while the WBK16 module is open. Always
remove bridge completion headers (CN-115) from the unit before soldering resistors
in the headers.

The CN-115-1 serves the same function as the CN-115 adapter plug and can be used for all of the same bridge
configurations detailed in the Configuration Diagrams section of this chapter. The CN-115-1 can be populatedwith either standard axial lead resistors or square precision resistors.
Each StrainBook (and WBK16) channel has a on-board 2×8 resistor socket with rows designated A through H.
CN-115-1 is a removable plug-in board that can be pre-configured for various bridge options.
It will often be the case that both the top and bottom (plug-in) sides of the CN-115-1 card will need to haveresistors installed to create the desired bridge configuration. The configurations are illustrated earlier in thechapter. In general, note that:ooo

WBK16, Strain-Gage Module

Half-bridge completion resistors consist of RG and RH (or RG1 and RH1).
Quarter-bridge completion resistors consist of RA, RC, and RE (or RA1, RC1, and RE1).
Shunt resistors consist of RB, RD, and RF (or RB1, RD1, and RF1).

949794

WBK16, pg. 19

In the example below CN-115-1 is being used to create a half-bridge configuration with two Bridge Completion
Resistors (BCRs) and three Shunt resistors. The half-bridge to the left (using standard resistors) is functionally thesame as the half-bridge on the right (using “precision” resistors). The center illustration represents an unpopulated
card to permit reading of the silk-screen.

Shown Unpopulated

Using Standard Resistors
BCR at “RG1”[Top Side of Card]

Using Standard Resistors

Using Precision Type Resistor[Top Side of Card]

BCR at “RG”

Shown Unpopulated

Using Precision Type Resistors[Plug-In Side of Card]

BCR at “RH1”
Shunts at “RB1” “RD1” “RF1”[Plug-In Side of Card][Top Side of Card]

BCR at “RH”
Shunts at “RB” “RD” “RF”
[Plug-In Side of Card]

For the functions listed in the preceding table, internal WBK16 configurations
still apply as indicated on pages 8 through 12 .

How to Interpret Resistor Connection Points
The CN-115-1 plug-in card’s silk-screen makes use of dual templates. For example, if we look at the RG / RG1
section [on the top side of the card] we will see a small resistor image “RG1” with lines connecting to two solder
points. Thus we know the connection points for standard resistors. If we are using a flat, relatively squareprecision-type resistor we would look at the square “RG” portion of the template (right image in the following
figure) and ignore the RG1 image. We can see that the lower left solder point remains, however, the second point
has changed.

Determining Solder Points for Resistor Leads

WBK16, pg. 20

949794

WBK16, Strain-Gage ModuleNote that the two half-bridges previously described are identical [circuit wise] to the one illustrated below,
which is being repeated from page 6.
The A thru H bridge-completion relations are the same, regardless of whether or not you choose to use a
CN-115-1 plug-in option. Refer to the configuration diagrams to set up your desired circuit(s).
+Sense+Excitation
RH

H BCR
G BCR
F Shunt
E
D Shunt
C
B Shunt
A

3

5

JN01 2

9

4

1

8

3

IA

7

2
6

RG

RF

RE

RD

RC

RB

DB-9
Input

RA

1
External
BridgeInternal Bridge Completion

Switches
accessedthroughsoftware-Excitation-SenseHalf-Bridge (+), Any Resistance from 60 to 1000 Ohms,
B,D, or F Shunt

Half-Bridge Circuit Created by using the CN-115 Header Only, i.e., no plug-in card
If present, read the manufacturer’s data that applies to your resistors. Important soldering andlead-bending information may be present.

CN-115-1 Mounting Orientation
When installing a CN-115-1 be careful to avoid bending the pins and ensure that the card is oriented in relation to
the DB9 connector as indicated below.

Jumper Pin Sections Must be Aligned

No Card Installed

Card Installed

The main Pins Must be Aligned with Corresponding Sockets

CN-115-1 Orientation, Shown for Channel 1

WBK16, Strain-Gage Module

949794

WBK16, pg. 21

Software Setup
WaveView contains special software features for WBK16. The WBK Sensor Configuration aspect of
WaveView is discussed in the following pages.
WBK16 support is only available with the 32-bit driver and 32-bit version of WaveView.

Reference Note:
For detailed information regarding non-WBK16 specific aspects of WaveView, refer to the
WaveView document. A PDF version of the document can be accessed from the dataacquisition CD via the <View PDFs> button on the CD’s opening screen.

Sensor Calibration
To use the Sensor Calibration Program you must first launch WaveView. This can be done from a shortcut
on the desktop, or by selecting WaveView from the Programs group, accessed from the desktop Start
menu.
WaveView holds user-configured parameters that can be saved to disk. The default configuration filename
is WAVEVIEW.CFG. When WaveView starts up, it proceeds to search the working directory for this file.
WaveView also holds a default sensor calibration file. The WAVEVIEW.CFG file holds the name of thiscalibration file so that all sensor calibration information from the last WaveView session is also loaded into
WaveView during initial boot-up. If the default configuration file is found, all the required setup
information will be extracted from it, and the application’s main window will open. When connection isestablished, the application’s main window will open with the default setting. If these options fail, a dialog
box will ask if you want to open a different setup file.
Reference Notes:
o For detailed WaveView startup information, refer to the WaveView PDF. The document
can be accessed from the data acquisition CD via the <View PDFs> button on the CD’s
opening screen.
o

WBK16, pg. 22

The WBK16/LC Load Cell Shunt Cal internal option board may be required to calibrateload cells and transducers that have internal shunt cal resistors. See the WBK16/LC
section of chapter 6 for details.

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WBK16, Strain-Gage Module

WaveView Configuration Main Window(Top) andSensor Configuration [Calibration] Window (Bottom)

To open the Sensor Configuration [Calibration] window, click on WaveView’s Sensor
Calibration button. The button is depicted at the left and pointed out in the upper portion of theprevious figure. You can also open the window from WaveView’s System pull-down menu.
You can use the Sensor Configuration window’s File pull-down menu to Load an Existing
Configuration. This option opens a standard dialog box that allows you to select and open thedesired file.

WBK16, Strain-Gage Module

949794

WBK16, pg. 23

Sensor Configuration Main Components

Sensor Configuration [Calibration] Window
Sensor Configuration Toolbar and Pull-Down Menus
Control functions in the sensor configuration window are available through the pull-down menus or the
toolbar. For descriptions of button functions, see the related menu selections. Note that some menu
selections have no corresponding button.

Sensor Configuration Window Toolbar
1 – New Configuration; 2 – Load an Existing Configuration; 3 – Save Current Configuration
4 – Take a Single Reading; 5 – Calibrate Enabled Channels; 6 – Return to WaveView

File
The File menu provides four functions:

New Configuration
Load an Existing Configuration
Save Current Configuration
Return to WaveView

WBK16, pg. 24

Set all parameters to their default startup setting.
Load a saved sensor calibration configuration.
Save the current sensor calibration configuration for later recall.
Exit the Sensor Configuration window and return to WaveView.

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WBK16, Strain-Gage Module

Calibration
The Calibration menu provides two functions:

Take a Single Reading
Calibrate Enabled Channels

This command allows the user to take a single reading and display the values in
the Sensor Configuration window.
This command will calibrate all enabled channels.

Password
The sensor calibration application provides password protection. If you calibrate any StrainBook channels[or WBK16 expansion channels] and then choose the password protection option WaveView will prevent
other users from making changes to your calibration file. The Password menu provides three functions:Enter Password
Set a New Password

Clear Password

WBK16, Strain-Gage Module

Use this command to enter a previously selected password, enabling you tochange parameters.
This command allows the user to select a 4-7 character password. A message
box will prompt you to enter a new password. Type a password and press“enter”, or click on the “OK” button.
This command clears the password protection. A message box will prompt you
to enter the current password. Type the current password and press “enter”, orclick on the “OK button.

949794

WBK16, pg. 25

Calibration Parameters Tab Selected

Sensor Configuration Window
ColumnDescription

Calibrate?

“Yes” enables the selected channel to be calibrated with the “calibrate enabled channels”
option. “No” prevents the channel from being calibrated. All other columns for that channel
will be disabled if “no” is selected. The channel can still be turned on in WaveView.
Provides a means of selecting the sensor type. The three available sensor types are:Strain Gage, Load Cell, and Transducer.
Provides a means of selecting the bridge type. Choices are full-bridge, half-bridge, andquarter-bridge. This option is only available for a strain gage sensor in the calibration
program. The bridge type for any sensor can be changed from the Sensor Configuration
window.
Allows the calibration method to be selected.
Possible selections are indicated in the
figure to the right. These calibration
methods are explained later in the
document.

Sensor Type
Bridge TypeCalibration Method

Calibration Date

Displays the time and date that the channel was calibrated. If the channel has not beencalibrated, “Not Calibrated” appears in the box.

Units

To change the units: highlight the desired box, type-in the new parameters, and then press<Enter> on the keyboard or select another box with the mouse. Up to 5 characters can beentered into this column. To fill the entire column with the value of channel one, make sure“yes” is selected in the “Calibrate” column. Then click on the column label with the mouse.
A message box will appear. Click on “yes”. All channels with the “calibrate” function
enabled will be filled. Changing the units here will also change the units column in the
WaveView Configuration main window.
Used to label channels.
A serial number or other identifying label for the sensor can be entered here. Up to 39
characters may be entered and 16 will be displayed. The fill option is available for thiscolumn (see Units).

Label
Sensor LabelWBK16, pg. 26

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WBK16, Strain-Gage Module

Calibration Parameters Section of Window
Two Views Obtained by Scroll Bar Movement
ColumnDescription

Exc. Volts

Used to change the excitation voltage. Choose between 10.0, 5.0, 2.0, 1.0, .5, and “Off.”
Changing the excitation voltage on any channel between one and four will change the valueon all four lower channels. Likewise, changing the excitation voltage on any channel fivethrough eight will change the value on all four upper channels. Changing the Excitation
Voltage here will also change the Source Level column in the WaveView Configuration
main window.
Used for calibrating strain gages with the Name Plate calibration method. To change thisvalue, select the box and enter a number greater than 0 and less than 1000. The fill option
is available for this column (see Units).
This column is used for calibrating a load cell or transducer using the Name Platecalibration method. To change this value, select the box and enter a number greaterthan 0 and less than 1000. The fill option is available for this column (see Units).
This column is used for calibrating any sensor using the Shunt calibration method. The
value must equal the value of the shunt resistor in ohms. To change the value, select thebox and enter a number greater than 0 and less than 1000000. The shunt value must notexceed the value entered as the maximum load. The fill option is available for this column(see Units).
Used for calibrating any sensor using the Shunt calibration method. The value refers to thebridge arm that is shunted during shunt calibration. To change the value, select the box andenter a number from 60 to 1000. The fill option is available for this column (see Units).
This column is used for calibrating a load cell or transducer using the Name Platecalibration method. To change this value, select the box and enter a number greater than 0
and less than 100000. The full-rated load must be greater than the value entered for the
maximum applied load. The fill option is available for this column (see Units).
Used for calibrating any sensor using any calibration method. To change the value, selectthe box and enter a number greater than 0 and less than 1000000. This value must be
greater than the quiescent/tare value. The fill option is available for this column (see Units).
This column is used for calibrating any sensor using any calibration method. The value
entered is the value of the quiescent load on the sensor. To change the value, select thebox and enter a number between –1000000 and 1000000. This value must be less than the
maximum applied load value. The fill option is available for this column (see Units).
This column is used for calibrating any sensor using the Shunt, or 2-Point Automatic
calibration method. The number must equal the input value, in mV, of the first point in thecalibration. To change the value, select the box and enter a number between -10000 and
10000. The fill option is available for this column (see Units).
This column is used for calibrating any sensor using the Shunt, 2-Point Automatic, or
2-Point Manual calibration method. The number must equal the value, in the selectedunits, of the first point in the calibration. To change the value, select the box and enter anumber between -1000000 and 1000000. The fill option is available for this column (seeUnits).
Used for calibrating any sensor using the 2-Point Automatic calibration method. The
number must equal the input value, in mV, of the second point in the calibration. To change
the value, select the box and enter a number between -10000 and 10000. The fill option isavailable for this column (see Units).
This column is used for calibrating any sensor using the 2-Point Automatic, or 2-Point
Manual calibration method. The number must equal the value, in the selected units, ofthe second point in the calibration. To change the value, select the box and enter a number
between -1000000 and 1000000. The fill option is available for this column (see Units).

Gage Factor

Sensitivity(mV/V)
Shunt Resistor(Ohm)

Bridge Resistor(Ohm)
Full Rated Load
(Units)Max Applied Load
(Units)Quiescent/Tare(Units)Point 1(mV)

Point 1
(Units)Point 2(mV)

Point 2
(Units)WBK16, Strain-Gage Module

949794

WBK16, pg. 27

Displaying a Single Reading. In the sensor calibration program, it is possible to take a single reading anddisplay it in the Sensor Configuration [Calibration] window. First, click on the Channel Values tab. Thenclick on the Take a Single Reading button on the tool bar, or choose Take a Single Reading from theCalibration menu item.
Displayed readings are based on the most recent calibration. Changing the calibration parameters,
without calibrating the system, will not affect the channel values.

Channel Values Tab Selected

Channel Values, Simplified Block Diagram
The simplified block diagram (above) can be used to better understand the relationship of channel amplifiers and theircorresponding user interface columns (visible in the Channel Values Tab). These columns are represented in the tab
figure, and in the following table.

Column

Display Description

Bridge (mV)
Input Gain

The input value from the bridge. The value is in millivolts.
The Gain setting of WBK16’s Input Amplifier. Any one of the following four settings is possible:
x1, x10, x100, or x1000.
The Voltage summed into WBK16s Scaling Amplifier. The voltage is to compensate for any
offset that is present in the sensor’s output. The Offset Null voltage is in the range of-3 to +3 volts.
The Gain setting of WBK16’s Scaling Amplifier. Any one of the following 13 gain settings canbe used: 1.0, 1.28, 1.65, 2.11, 2.71, 3.48, 4.47, 5.47, 7.37, 9.46, 12.14, 15.58, or 20.0.
The digital voltage value that is received as input by WaveView software. This value is also
referred to as sensor output voltage.
The Multiplier value [used by the software] for converting sensor output voltage into User Units.
The Offset value that is added to “Units Scaling” for fine adjustment of what will be the final
reading (Bridge Units).
The Reading (in User Units, for example: lbs, psi, kg) that results from converting the initial
sensor reading (Bridge mV).

Offset Null (Volts)

Scaling Gain
A/D In (Volts)
Units Scaling
Units Offset
Bridge (Units)

WBK16, pg. 28

949794

WBK16, Strain-Gage Module

The Five Methods of Sensor Calibration
Before proceeding with calibration, remember to enter your password. The password
must be entered before channel parameters can be changed.
Unless all of the parameters (for each channel to be calibrated) are accurately enteredinto the spreadsheet, the calibration will produce incorrect results.

The sensor calibration program uses five methods of calibration:
o
o
o
o
o

2-Point Manual
2-Point Automatic
Shunt (Internal)
2-Point Shunt (External)
Name Plate (for load cell or transducer)

Table of Calibration Methods and Required Parameters
Excitation

Gage
FactorSensitivity

Shunt
Ohms

Bridge
Ohms

Full
Load

Max.
Load

Quiescent

Pt-1

Pt-1

Pt-2

Pt-2

(mV)

(Units)(mV)(Units)2 Point
Manual9992 Point
Auto

9

9

9

Shunt
(Internal)

9

9

9

9

2 Point
Shunt(External)

9

9

9

9

Nameplate

9

9

9

9

9

9

9

9

9
9

9

9
9

9

9

9

To use any of these calibration methods, enter the appropriate values into the required spreadsheet columnsof the Sensor Calibration window, as listed above, and click on the Calibrate Enabled Channels button on
the toolbar.
In 2-Point Manual calibration, a message box prompts you to apply the first load. When
prompted, apply the load and click the OK button. A second message box will prompt
you to apply the second load. When prompted, apply the second load and click <OK>.

Saving a Calibration File. After calibrating the enabled channels, a message box asks if you want to savethe changes. Click on the Yes button to save the calibration and a dialog box will appear. If you choose notto save the changes at this time, another message will appear asking if you want to save the changes when
you click on the Return to WaveView button on the tool bar. Click on the Yes button to save these changes
and a dialog box will appear. The most recently saved calibration file will be recorded in the
WAVEVIEW.CFG default configuration file and will be loaded into WaveView whenever a new session isstarted. The current configuration can also be saved from the toolbar or File menu item.

WBK16, Strain-Gage Module

949794

WBK16, pg. 29

2 Point Manual Calibration
In the 2 Point Manual Calibration method two readings are taken from the gage with different loads applied for eachreading. For this method, the user must enter the following 5 parameters:
Excitation - The value of the constant voltage source used to excite the gage.
Max Load - The maximum load value the gage is expected to measure. This value could be less than the
max rated load of the gage.
Quiescent Load - The minimum load value the gage is expected to measure. This value could be greaterthan the min rated load of the gage.
Point 1 Units -The load that will be placed on the gage for the first calibration measurement.
Point 2 Units - The load that will be placed on the gage for the second calibration measurement.
Example: Excitation voltage is set to 10 volts. A strain gage with a full load rating of +/- 1000 µe is connected toa StrainBook [or WBK16] channel. However, the gage will be used in an environment were the expected range ofmeasurement is limited to 0 to 600 µe. Two certified loads of 50 µe and 500 µe are available for calibration. In
the Calibration Parameters spreadsheet, the user would enter the values as follows:
Excitation = 10V
Max Load = 600
Quiescent Load = 0
Point 1 Units = 50
Point 2 Units = 500

1.
2.
3.
4.
5.

When the <Calibrate Enabled Channels> toolbar button is pressed, the user is prompted to load the gagewith 50 µe.
After the load is applied, and the <Ok> button pressed, WaveView takes several voltage readings in an
attempt to find the best gain setting for the first load value.
When finished, the user is prompted to load the gage with 500 µe.
After the load is applied, and the <Ok> button pressed, WaveView again takes several measurements tofind the best gain settings for the second load value.
After both voltage measurements are obtained, WaveView configures the input channel to provide theoptimum settings for the two amplifier gain stages, and the Offset DAC. WaveView also sets thechannels mX+b parameters for proper conversion of the input voltage measurements to units of µe (orwhatever units have been specified by the user).

Note: The greatest accuracy is obtained from 2 Point Manual calibration when the two calibration points are at themin and max load range of the gage. In the above example, the greatest possible accuracy would beobtained if Point1 was equal to the Quiescent load, and Point 2 was equal to the Max load.

2 Point Auto Calibration
For 2 Point Auto Calibration the user must enter the following 7 parameters:
Excitation - This is the value of the constant voltage source used to excite the gage.
Max Load - Is the maximum load value that the gage will be expected to measure. This value could beless than the max rated load of the gage.
Quiescent Load - Is the minimum load value that the gage will be expected to measure. This value could
be greater than the min rated load of the gage.
Point 1 mV - This is the output voltage generated by the gage at the Point 1 Units load.
Point 1 Units - This is the load that is associated with the Point 1 millivolt value.
Point 2 mV - This is the output voltage generated by the gage at the Point 2 Units load.
Point 2 Units - This is the load that is associated with the Point 2 millivolt value.
No actual readings are taken when a 2 Point Auto Calibration is performed. Calibration constants are calculated
from the values entered by the user.

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WBK16, Strain-Gage ModuleShunt (Internal Shunt) Calibration
The Shunt calibration method pertains to an internal shunt. For this method two readings are acquired from abridge. The first reading is obtained with the bridge in its quiescent state; the second is taken with one leg of thebridge shunted by one of three selectable resistors. The resistors are located on a plug-in header inside theStrainBook or WBK16 module. Shunt calibration appears as "Shunt (RB)", "Shunt (RD)", and "Shunt (RF)" in thelist of calibration methods.
The Internal Shunt Calibration requires that the user enter the following 7 parameters:
Excitation - The value of the constant voltage source used to excite the gage.
Gage Factor - The Gage Factor value of the gage used in the bridge. A Gage Factor of 2 is typical.
Shunt Ohms - The value in Ohms of the shunt resistor mounted on the header inside the StrainBook or
WBK16 module.
Bridge Ohms - The resistance value of the gage. Typically 120 or 350 Ohms.
Max Load - The maximum load value the gage is expected to measure. This value could be less than the
max rated load of the gage.
Quiescent Load - The at rest value of the load applied to the gage. If no load will be applied to the gage inits quiescent state, enter “0” zero.
Point 1 Units - The minimum load value the gage is expected to measure. This value could be greater thanthe minimum rated load of the gage.
Example: Excitation voltage is set to 2 volts. A Quarter Bridge circuit employing a 350 Ohm strain gage with aGage Factor of 2 and a full load rating of +/- 1500 µe is connected to a StrainBook [or WBK16 channel]. The gage
will be used in an environment were the expected range of measurement is limited to -200 to +1000 µe. This gage[in its quiescent state] has a 500 µe load. A 349,650 Ohm precision resistor is available that will be mounted on theplug-in header in Shunt location R(B). Instructions for installing shunt resistors are provided elsewhere in the
document. In this example the user would enter the following values in the Calibration Parameters spreadsheet:
Cal Method Shunt R(B)
Excitation = 2V.
Gage Factor = 2
Shunt Ohms = 349,650
Bridge Ohms = 350
Max Load = 1000
Quiescent Load = 500
Point 1 Units = -200

The accuracy of Shunt Calibration is directly related to the tolerances of the Shunt resistor, Gage(s), and Bridge
Completion resistors used in the circuit. In the event that a precision shunt resistor is unavailable, WaveView
provides an alternate way of calculating Shunt calibration constants. This method is as follows:(a) Install an appropriate non-precision shunt resistor of a value that creates the degree of bridge
imbalance desired.
(b) Press and hold the <Alt> key on the computer’s keyboard; then start the calibration process.
(c) Once the calibration process has started you release the <Alt> key.
This alternate Shunt Calibration method calculates the shunted load value from shunted and un-shunted bridge
voltage measurements; and then performs the equivalent of a 2 Point Manual calibration.

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WBK16, pg. 31

External Shunt Calibration (2 Pt Shunt)
This calibration method requires the use of a WBK16/LC option, which is discussed elsewhere in the document.
The method supports the use of an external shunt resistor. The resistor is shunted across the gage using the (RF)switch in the StrainBook or WBK16. The method appears simply as "Shunt" in the list of calibration methods
when either “Load Cell” or “Transducer” is selected as the sensor type.
Note: The WBK16/LC provides a non-committed dry contact on two pins of a single StrainBook or WBK16
channel connector. The WBK16/LC can be used for virtually all single value shunt calibration requirements,
some of which are not possible with the internal FET/analog switch provisions in the standard channel
configurations.

WBK16/LCCAUTION
Make the DB9 pin # 2 connection to the “low-side” or the “high-side” of thecircuit. BUT NEVER TO BOTH! Doing so will create a short circuit that could
damage equipment.
External Shunt Resistor, Low-Side Connection

Full Bridge (+) with External Shunt Resistor
DB9 Pin 2 Connected to the Low-Side
Reference Note:
The WBK16/LC Load Cell Shunt Cal internal option board is detailed in an early section.
That section includes an alternate schematic for connecting Pin 2 to the High-side.

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WBK16, Strain-Gage Module

The External Shunt Calibration method requires that the user enter the following 5 parameters:
Excitation - The value of the constant voltage source used to excite the gage.
Max Load - The maximum load value that the gage is expected to measure. This value could be less thanthe max rated load of the gage.
Quiescent Load - The minimum load value that the gage is expected to measure. This value could begreater than the minimum rated load of the gage.
Point 1 Units - The user-supplied, at rest value of the load applied to the gage. If no load is applied to thegage in its quiescent state, enter “0”zero.
Point 2 Units - The user-supplied effective load value that will appear at the gage when the external shunt
resistor is switched into place. This load value must be calculated based on the value of theexternal shunt resistor.
As with the Internal Shunt method, calibration accuracy is directly tied to the accuracy and stability of the shunt
resistor used.

Name Plate Calibration
Name Plate Calibration is similar to the 2 Point Auto Calibration method. No actual measurements are taken
during the calibration process. The calibration constants are calculated from information provided by the user. The
method is called “Name Plate” because the calibration information is obtained from the Name Plate or Label that is
attached to the gage or load cell.
The Name Plate Calibration method requires that the user enter the following 5 parameters:
Excitation - The value of the constant voltage source used to excite the gage.
Sensitivity - The output of the gage measured in millivolts per volt.
Full Rated Load - The maximum rated load of the gage.
Max Load - The maximum load value that the gage will be expected to measure. This value could be lessthan the max rated load of the gage.
Quiescent Load -The minimum or at rest value of the load applied to the gage. If no load is applied to thegage in its quiescent state, enter zero. WaveView assumes the Min Load value is equal to thequiescent load value.
Calibration Example using the Name Plate Method and a Load Cell
The following example uses Name Plate calibration with a load cell.
Load cells come with a mV/V specification (frequently referred to as sensitivity) which means for each voltof excitation at maximum load, the load cell will output a specific millivolt level.
Consider a 3000-pound load cell rated at 3 mV/V using 10 V of excitation. When the load cell is used,
a 10-pound platform will be placed on it. Although the load cell is rated at 3000 pounds, 1500 pounds isthe maximum load that will ever be applied for this example.
From the above data we know the following parameters:
•
•
•
•
•

Excitation Voltage = 10 volts
Maximum Applied Load = 1500 pounds
Quiescent Tare = 10 pounds
Sensitivity = 3 mV/V
Full Rated Load = 3000 pounds

Note: These 5 values are used in the following figure.

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WBK16, pg. 33

To calibrate this load cell using the sensor calibration program:
1.
2.
3.
4.

Enter the 5 necessary parameters (see preceding bulleted list) into the calibration spreadsheet. These
values are used in the following figure, in which a load cell is connected to channel 7-1.
Once the parameters are entered into the spreadsheet, select Calibrated Enabled Channels either fromthe menu bar or from the tool bar.
After the calibration is complete, the sensor calibration program will ask you if you want to save thecalibration data.
The calibration is now complete. To use the load cell, exit the Sensor Calibration window and returnto the main WaveView Configuration main window.

Calibration (View of window with scrollbar to the left)

Calibration (View of window with scrollbar to the right)

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WBK16, Strain-Gage Module

Changing Low-Pass Filter Displays
To change the LPF display, choose Advanced Features from the System menu item. Enter desired values inthe LPF Corner Frequencies Settings dialog box. The frequency range for the first LPF setting is 2Hz to
200Hz. The frequency range for the second LPF setting is 200 Hz to 20000 Hz.
Making changes to the “LPF Settings” or the “LPF Cutoff Column”(of WaveView’s Main
Window) will not result in any change to the actual filter. You must physically change
frequency cutoff selection resistors so they correspond with the values indicated by thesoftware (or visa versa).
Reference Note:
For information on customizing the Low-Pass Filters refer to Low-Pass Filter Customizationin Chapter 6, Bridge Configurations.

Accessing the LPF Corner Frequencies Dialog Box

Note: The LPF Corner Frequencies Dialog Box is accessed from WaveView’s main windowby selecting Advanced Features from the System pull-down menu.

Reference Note:If creating your own programs, refer to the Programmer’s Manual, p/n 1008-0901, as needed.

PDF Note:

WBK16, Strain-Gage Module

During software installation, Adobe® PDF versions of user manuals automatically install onto
your hard drive as a part of product support. The default location is in the Programs group,
which can be accessed from the Windows Desktop. Refer to the PDF documentation for details
regarding both hardware and software.

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WBK16, pg. 35

WBK16 – User Tips
There are some aspects of the WBK16 that can cause user difficulties if misunderstood. The following
tips should increase your level of understanding and help you get the most out of your WBK16.

(1) Keep things cool.
Operating 120 ohm bridges on 10 volts of excitation is possible with the WBK16 but the strain gages andbridge completion resistors must both be rated for this voltage or there will be excessive drift as the gages
and resistors heat up. The 120 ohm bridge completion resistors we offer (part number R-17-120) are of
insufficient power rating for 10 volt bridges. If the excitation level is set to 5 volts, drift is not a problem
with our 120 ohm resistors. An alternative is to purchase higher quality, higher power and higher cost
bridge completion resistors (part number S-120-01) from the Measurement Group.

(2) Understand the difference between calibration and set-up.
Calibration requires measurements of channels with external wiring and gages connected to establish
computational data on which to base gain and offset settings. The two-point manual and shunt cal menu
choices provide calibration. Set-up uses manually entered parameters to computationally choose gain andoffset settings. The two-point automatic and nameplate menu choices provide channel set-up.
The nameplate menu selection for strain gages cannot effectively calibrate field configured strain gagebridges which have not been externally hardware nulled because the software algorithm assumes the zero
point and computes the other settings based on the excitation voltage, gage factor and full scale value
entered by the user. Nameplate “calibration” is intended for packaged and pre-calibrated devices, such asload cells and pressure transducers with nameplates listing their output sensitivity in mV/V and full-scale
output in engineering units.

(3) Do not attempt to “calibrate” all the channels simultaneously.
Although desirable, it is not possible, to globally calibrate all the channels without making any actual
measurements. It is possible to apply global auto-zero to previously calibrated channels that have auto-zeroenabled. However, the original requirement for the channel to have been externally nulled, prior toperforming nameplate calibration remains. The overall settings for all of the channels can be stored as aconfiguration for re-use, but assuming the overall calibration and external system are unchanged between
chronologically separated tests is risky and not recommended.

(4) Know an unbalanced bridge when you configure one.
Theoretically, a strain gage bridge is balanced with zero output until strain is applied producing an output
voltage linearly proportional to the strain. In the real world, the bridge is slightly unbalanced due tocomponent tolerances. There are two approaches to allow accurate strain measurements with the slightly
unbalanced bridge, (1) balance the bridge, or (2) compensate for the error with correction factors.
Understand that if you do neither, the bridge will provide erroneous results.

(5) Take it easy on the excitation regulators.
The excitation outputs of the WBK16 will deliver up to 90 mA without any degradation in output voltage.
If this level of current is exceeded, the voltage is reduced to protect the regulator. It is important toconsider the current drawn by the internal reference node resistors. These resistors are never switched off,
they continue to load the excitation regulator no matter what bridge configuration is chosen. If these
resistors are 120 ohm resistors, which they never really need to be, they draw 41.7 milliamps at 10 volts.
An external full bridge of 120 ohm resistors, and requiring an additional 83.3 milliamps will definitely
overload the regulator and result in a reduced excitation level and an incorrect signal level. For two
reasons, the best choice for the reference node resistors is 1000 ohms. The parts will draw less excitation
current, helping the regulators and the lower degree of self-heating will result in less drift.

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WBK16, Strain-Gage Module(6) Provide adequate input power to each WBK16 in a system.
Providing the proper level of input supply voltage is very important. Insufficient input voltage can cause
the WBK16 to exhibit channel-to-channel excitation interaction. All individual channels can be set
properly and then begin to lose voltage as additional channels are connected. It is imperative that the
WBK16 not be “starved” for input voltage. This can very easily happen if more than one WBK16 is
powered from the supplied TR-40U power adapter or some other smaller and inadequate source. A
WBK16 can require as much as 25 watts of input power if configured for eight channels of 120 ohm
bridges at 10 volts of excitation. The 15V, 2.4A (36 watts) output of the TR-40U is not sufficient for two
WBK16’s. A variation of this problem can occur if a group of WBK16’s is daisy-chained together withan insufficient wire size feeding the group. Voltage drop in the wiring can also starve the WBK16’s to agreater degree as distance from the source increases. It is strongly recommended that individual WBK16
units each operate from the TR-40U provided or from an individual power lead from an adequately sized
source such as a large battery or power supply.

(7) Handle channel configuration headers carefully.
The 16-position, machined-pin IC sockets [into which the bridge completion headers are inserted] havedemonstrated a tendency to become unreliable if the headers are rocked sideways to remove them or if
resistors with larger leads than those we supply are plugged directly into them. The unreliability manifests
itself with widely fluctuating readings, especially if touched, or if the WBK16 enclosure is subjected toshock or vibration. Cold solder joints on the headers have similar symptoms.

(8) Install internal reference node resistors if you plan to use half or quarter bridges
There are internal 1 Meg ohm bias resistors [located between the excitation rails] that create a very highimpedance “reference node voltage” in the WBK16 without installing the recommended resistors. Do not
attempt measurements using these default resistors, even though it seems to work. Install the previously
recommended 1000 ohm components and use a calibration method which compensates for the slight bridge
imbalance.

(9) Do not neglect the excitation regulator remote sense leads.
The remote sensing feature of the WBK16 will compensate for voltage drop in long lead wires to provide
accurate excitation levels at the terminals of full-bridge and half-bridge configurations. If the remotesense lines are not used, be sure to tie them to their respective output lines to minimize excitation noise.

(10) Spend your resistor dollars wisely.
For the widely used 3-wire quarter bridge configuration, purchase the lower bridge completion resistor(RA) with the best available temperature coefficient and sufficient power rating as to minimize self-heating.
The tolerance of the resistance is not as critical, but it should be 0.1% or better. The internal bridge
completion locations for the reference node (RG and RH) have about 50 milli-ohms resistance between their
midpoint connection pads and the tap to the amplifier is at the lower end of this resistance. This resistancenullifies the benefit of using bridge completion resistors with better than 0.1% resistance tolerance because
offset nulling will still be necessary. If using shunt calibration, purchase high-precision shunt calibration
resistors with micro-strain values appropriate to your application. These are the closest to “standards,”
short of a very high precision strain calibrator.

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WBK16, pg. 37

WBK16 – Specifications
Name/Function: Strain-Gage Module
Number of Channels: 8
Input Connector: Standard female DB9 per channel
Input Type: Differential
Input Impedance: 100 MΩ
Coupling: AC and DC, software selectable
Accuracy:
Offset Drift: 1µV RTI/°C
CMMR @ DC to 60 Hz: 100 dB at gains > 100
Cross-Talk Rejection: > 90 dB @ less than 1 kHz
Bandwidth:
50 kHz @ gains < 1 to 100
10 kHz @ gains > 100 to 2000
1 kHz @ gains > 2000
Bridge Configuration:
Full-bridge (4- and 6-wire)Half-bridge
Quarter-bridge (2- and 3-wire)
Bridge Completion: User supplied resistors on removable headers (included)
Bridge Resistance: 60 to 1000 Ω
Overall Gain: 1 to 20000, software selectable in 86 steps
Shunt Calibration: software selection of 3 user-supplied resistors
Auto-Balance: Selected per channel
Auto-Calibration: Either by actual measurement or by calculated load
Offset Adjustment:±3 V RTI @ gains 1 to 10±300 mV RTI @ gains 10 to 100±30 mV RTI @ gains 100 to 2000
±3 mV RTI @ gains 2000 to 20000
Excitation Source: Two independent banks can be set to 0.5, 1.0, 2.0, 5.0, 10.0 volts or off
Excitation Accuracy: ±5 mV
Excitation Capacity: 85 mA per channel with fold-back current limiting
Filtering: 4-pole Butterworth, software-selectable and factory-set to 10 Hz, 1 kHz, or bypass;field-changeable
Input Power Voltage Range: 10-30 VDCPower Consumption: 1.0A @ 15V (min);
1.7A @ 15V (max)Operating Temperature: 0° to 50°C
Storage Temperature: 0° to 70°C
Humidity: 0 to 95% RH, non-condensing
Dimensions: 221mm x 285mm x 35mm (8.5” × 11” × 1.375”)
Weight: 1.32 kg (2.9 lb)

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