Dewetron DAQP-CFB2 Product manual

TECHNICAL REFERENCE MANUAL
DAQP-CFB2 Module
WELCOME TO
THE WORLD OF
DEWETRON!
Congratulations on your new device! It
will supply you with accurate, complete
and reproducible measurement results
for your decision making.
Look forward to the easy handling and
the flexible and modular use of your
DEWETRON product and draw upon
more than 30 years of DEWETRON
expertise in measurement engineering.
ISO9001
EN ISO 14001
THE MEASURABLE DIFFERENCE.

Copyright © DEWETRON GmbH
This document contains informaon which is protected by copyright. All rights are reserved. Reproducon,
adaptaon, or translaon without prior wrien permission is prohibited, except as allowed under the copyright
laws.
All trademarks and registered trademarks are acknowledged to be the property of their owners.

3
Notice
General Information, Safety Instructions
The information contained in this document is subject to change without notice.
DEWETRON GmbH (DEWETRON) shall not be liable for any errors contained in this document.
DEWETRON MAKES NO WARRANTIES OF ANY KIND WITH REGARD TO THIS DOCUMENT, WHETHER
EXPRESS OR IMPLIED. DEWETRON SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. DEWETRON shall not be liable for
any direct, indirect, special, incidental, or consequential damages, whether based on contract, tort, or any
other legal theory, in connection with the furnishing of this document or the use of the information in this
document.
Warranty Information:
A copy of the specic warranty terms applicable to your DEWETRON product and replacement parts can be
obtained from your local sales and service o󰀩ce.
Restricted Rights Legend:
Use austrian law for duplication or disclosure.
DEWETRON GmbH
Parkring 4
8074 Grambach
Austria
Printing History:
Please refer to the page bottom for printing version.
Copyright © DEWETRON GmbH.
This document contains information which is protected by copyright. All rights are reserved. Reproduction,
adaptation, or translation without prior written permission is prohibited, except as allowed under the copyright
laws.
All trademarks and registered trademarks are acknowledged to be the property of their owners.
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

4
Notice
Safety symbols in the manual
Indicates hazardous voltages.
WARNING Calls attention to a procedure, practice, or condition that could cause bodily
injury or death.
CAUTION Calls attention to a procedure, practice, or condition that could possibly cause
damage to equipment or permanent loss of data.
WARNINGS
The following general safety precautions must be observed during all phases of operation, service, and
repair of this product. Failure to comply with these precautions or with specic warnings elsewhere in this
manual violates safety standards of design, manufacture, and intended use of the product. DEWETRON
Elektronische Messgeraete Ges.m.b.H. assumes no liability for the customer’s failure to comply with these
requirements.
All accessories shown in this document are available as option
and will not be shipped as standard parts.

5
Safety Instructions
Safety instructions for DEWETRON amplifiers
The DEWETRON data acquisition systems and ampliers may only be installed by experts.
Read your manual carefully before operating.
Observe local laws when using the ampliers.
Ground the equipment: For Safety Class 1 equipment (equipment having a protective earth terminal), a
non interruptible safety earth ground must be provided from the mains power source to the product input
wiring terminals or supplied power cable.
DO NOT operate the product in an explosive atmosphere or in the presence of ammable gases
or fumes.
DO NOT operate damaged equipment: Whenever it is possible that the safety protection features built
into this product have been impaired, either through physical damage, excessive moisture, or any other
reason, REMOVE POWER and do not use the product until safe operation can be veried by service-
trained personnel. If necessary, return the product to a DEWETRON sales and service o󰀩ce for service
and repair to ensure that safety features are maintained.
Keep away from live circuits: Operating personnel must not remove equipment covers or shields.
Procedures involving the removal of covers or shields are for use by service-trained personnel only.
Under certain conditions, dangerous voltages may exist even with the equipment switched o󰀨. To avoid
dangerous electrical shock, DO NOT perform procedures involving cover or shield removal unless you
are qualied to do so.
No modications are allowed at the ampliers.
DO NOT service or adjust alone. Do not attempt internal service or adjustment unless another person,
capable of rendering rst aid and resuscitation, is present.
DO NOT substitute parts or modify equipment: Because of the danger of introducing additional hazards,
do not install substitute parts or perform any unauthorized modication to the product. Return the product
to a DEWETRON sales and service o󰀩ce for service and repair to ensure that safety features are
maintained.
DO NOT touch internal wiring!
DO NOT use higher supply voltage than specied!
Use only original plugs and cables for harnessing.
Safety of the operator and the unit depend on following these rules.
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

6
Support
For any support please contact your local distributor rst or DEWETRON directly.
For Asia and Europe, please contact:
DEWETRON GmbH
Parkring 4
8074 Grambach
AUSTRIA
Tel.: [phone]
Fax: [phone]
Email: [email protected]
Web: http://www.dewetron.com
The telephone hotline is available Monday to Friday between 08:00 and 12:00 CET (GMT -1:00) and Monday
to Thursday between 13:00 and 17:00 CET.
For the Americas, please contact:
DEWETRON, Inc.
2850 South County Trail, Unit 1
East Greenwich, RI 02818
U.S.A.
Tel.: [phone]
Toll-free: [phone]
Fax: [phone]
Email: [email protected]
Web: http://www.dewetron.us
The telephone hotline is available Monday to Friday between 08:00 and 17:00 GST (GMT +5:00)

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7
General Module Information
9-pin male SUB-D connector
Interface pin assignment:
1 Module output (±5 V)
2 RS-485 (A)
3 RS-485 (B)
4 GND
5 +9 V power supply
6 +12 V power / sensor supply
7 Module input (from D/A
converter of the A/D board)1)
8 reserved
9 -9 V power supply
1) Triggerout at DAQP-FREQ-A
Calibration information
All DEWETRON modules are calibrated at 25 °C after a warmup time of 30 minutes and meet their
specications when leaving the factory.
The time interval for recalibration depends on environmental conditions. Typically, the calibration should be
checked once a year.
Calibration certicates are available from DEWETRON as an option. DEWETRON o󰀨ers two types:
ISO traceable DEWETRON certicate
Calibration certicate according to ÖKD (equivalent to DKD)
This manual contains no calibration information. For self calibration, there is a separate calibration kit for the
DAQ series modules available. The CAL-KIT contains the required cables, software and instructions.
General module specifications
Module dimensions: 20 x 65 x 105 mm (0.79 x 2.56 x 4.13 in.)
(W x H x D without front cover and connectors)
Frontcover: 20 x 87 x 2 mm (0.79 x 3.43 x 0.08 in.)
(W x H x D without connector)
Environmental:
Temp. range storage: -30 °C to +85 °C (-22 °F to 185 °F)
Temp. range operating: -5 °C to +60 °C (23 °F to 140 °F)
Relative humidity
(MIL202): 0 to 95 % at 60 °C, non-condensing (unless otherwise noticed)
RFI susceptibility: ±0.5 % span error at 400 MHz, 5 W, 3 m
All specications within this manual are valid at 25 °C!
All modules are produced according ISO9001 and ISO14001.
Module connectors
Frontpanel connector: Accessable to the user. The connector type and pin assignment varies
from module to module. Detailed pin assignment of each module is
shown in the appropriate module description.
Rear connector: 9-pin male SUB-D, interface to the DEWE-System, not accessable to the user.
HSI/DAQx and PAD module
rear view
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

DEWETRON
data acquisition
system
RS-232/485
conversion on
DEWETRON-
motherboard
DAQx or PAD
module
RS-232
interface
RS-485
businterface
8
RS-232/485 interface
HSI/DAQP modules can be congured via
RS-485 interface, PAD modules require
this interface for all data transfers.
For all DEWETRON systems, an internal
RS-232/485 converter is available
(standard with DEWE-800, -2000, -2500, -3000, -4000, -5000 series systems). This converter allows
communication with HSI/DAQP and PAD modules.
To communicate with the modules, the RS-232 interface has to be set to the following parameters:
baud rate: 9600 bps
data bits: 8
parity: no parity
stop bits: 1
handshake: not required
HSI/DAQP module configuration
1. Push button selection
All ranges and lters can be selected directly by pressing the push buttons on the module. Approx. 15 sec.
after changing range and / or lter, the range and lter information is stored in an EEPROM. This procedure
increases the livetime of the EEPROM.
The current input range setting is shown all the time by LED. To change the range just press RANGE button
a few times until the required range is displayed.
To see the current lter setting just press the FILTER button once. The corresponding LED is ashing for
approx. 3 seconds. Within this time, the lter can be selected by pressing the FILTER button again. Approx.
3 seconds after the last key activity, the information will be stored, the LED stops ashing and shows the
input range again.
CAUTION: Power loss during this time leaves the module in the former settings.
2. RS-232/485 programming
All ranges and lters can also be selected via RS-232/485 interface. All new DEWE-800, -2000, -2500,
-3000, -4000, -5000 series systems are prepared as a standard to work with HSI/DAQP modules.
The easiest way to change the conguration is to use the DEWECong software, which comes as a standard
with the DEWETRON data acquisition system.
Detailed information about HSI/DAQP modules programming for customer applications is available in the
DEWE-Modules Programmers Reference Manual.
CAUTION: All range and lter changes which are done via RS-232/485 interface are not stored in the
EEPROM of the HSI/DAQP modules! You have to store this information in a separat initialisation le to
keep settings information for next system start!
PAD module communication
All PAD modules are only working through the RS-232/485 interface. All new DEWE-800, -2000, -2500,
-3000, -4000, -5000 series systems are prepared as a standard to work with PAD modules. The easiest
way to change the conguration is to use the DEWECong software, which comes as a standard with the
DEWETRON data acquisition system.
Detailed information about PAD modules programming for customer applications is available in the
DEWE-Modules Programmers Reference Manual.
General Module Information

9
DAQP-CFB2
Carrier frequency amplifier
Bandwidth: max. 9.6 kHz
Input ranges: Bridge: 0.1 mV/V to 1000 mV/V
LVDT: 5 mV/V to 1000 mV/V
Capacity: 20 pF to 1 µF
Sensor Excitation: Programmable voltage and frequency up to
5 VRMS / 20 kHz; remote sense support
Bridge completion: Internal completion for ½ and ¼ bridge
(120 and 350 Ω)
Shunt: Two internal shunts (50 kΩ, 100 kΩ)
TEDS: Support for TEDS sensors
Module specifications
DAQP-CFB2
Bridge input ranges 0.1 mV/V to 1000 mV/V
Inductive bridge input ranges 5 mV/V to 1000 mV/V
Capacitive input Ranges 20 pF to 1 µF
Bridge resistance 60 - 5000 Ω depending on excitation voltage
Excitation voltage level 1, 2, 5 VRMS sensed excitation provided
Excitation voltage accuracy 0.05 % of value ± 200 µV
Excitation voltage frequency 0.6; 1; 2.5; 5; 10; 20 kHz sine wave ±100 ppm
Maximum excitation current 50 mARMS short circuit protected
Excitation voltage synchronisation internal crystal oscillator or external
Excitation voltage drift typically 20 ppm/K
Excitation frequency drift typically 2 ppm/K
Nonlinearity ±0.02 % FS
Accuracy bridge mode typically ±0.1 % of reading ±0.05 % of range
Max. o󰀨 set drift ±0.003 µV/V/K ±40 ppm of Range/K
Max. gain drift ±30 ppm/K
Balance adjusting range ±400 % of Range (±200 % at 1 V excitation)
Phase adjustment range ±90° (inductive mode only)
Balance adjusting accuracy within ±0.1 % FS
Supported sensors 4- or 6-wire full bridge
3- or 5-wire ½ bridge with internal completion (software programmable)
3-wire ¼ bridge with internal resistor for 120 and 350 Ω (software programmable)
inductive full bridge
inductive half bridge (typically LVDT Sensors)
Shunt calibration internal 50 kΩ and 100 kΩ Shunt
Completion and shunt resistor accuracy ±0.05 %
-3 dB Bandwidth max 9.6 kHz
Reconstruction  lter 7th order Butterworth, automatically adjusted to excitation frequency * 0.48
Signal  lters (low pass) 10, 30, 100, 300, 1 kHz, 3 kHz
Filter characteristics 2nd order Bessel or Butterworth (40 dB/ decade)
Typ. SNR @ 1000 Hz [100 Hz] 78 dB [85 dB] @ 1 mV/V
and 2 VRMS excitation 80 dB [87 dB] @ 100 mV/V
Over voltage protection ±10 V
Output voltage ±5 V
Out current ±5 mA
Output protection continuous short to ground
Power consumption max. 1.5 W
Supported TEDS chips DS2406, DS2430, DS2432, DS2433, DS2431
Weight within 250 (±30) g
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10
DAQP-CFB2
General description
The signal path of the DAQP-CFB2 is completely analog. This reduces the signal delay to the absolute
minimum, which is a huge advantage in comparison to a DSP based bridge amplier with AD and DA
conversion. DSP based bridge ampliers always have a delay due to the calculation. The analog design
makes the DAQP-CFB2 a perfect choice for control loop applications, where a fast response is required.
The main advantages of the carrier frequency technology are:
eliminating thermo voltages
extremely low 1/f noise
electrical disturbances like the 50/60 Hz signal are totally suppressed
very high o󰀨set stability
The typical applications for this module are:
Long term strain measurement
Strain gage measurement in harsh electromagnetic environment
LVDT sensor measurement
Capacitive sensor measurement
Frontend amplier for control loops
Test-bed signal conditioning
The DAQP-CFB2 replaces the older DAQP-CFB module. The new module has a higher accuracy and
supports many more features. Despite of all improvements, it is still compatible with the older DAQP-CFB.
Even the standard command set, except custom range settings, is downward compatible. Replacing the old
CFB by the new one should not require any changes in terms of sensor connection.
Front panel control
LED indication:
Filter Range Range Filter
B.W. 5 mV/V x100 300 Hz
2 mV/V x10 100 Hz
3000 Hz 1 mV/V x1 30 Hz
10000 Hz Cust. x0.1 10 Hz
The DAQP-CFB series module has a set of 8 LEDs showing the current input range (constant active)
and lter range setting (ashing). Functions are described below.
Push button operation:
Assign module address: Press the ID button for allowing the software to change the address.
Select range : Push the RANGE button several times shortly until the LED displays the
desired input range.
Select Filter: Push the FILTER button once - the LEDs will ash for approx. 3 seconds
and display the current lter setting. Push the FILTER button within the
three seconds several times until the ashing LED displays the desired lter
range.

11
DAQP-CFB2
120 Ω
100 kΩ
±7 V
±7 V, 50 mA
100 kΩ
TEDS
100 Ω 33 pF
33 pF 100 kΩ
Inductive
full bridge
100 Ω
100 kΩ
350 Ω 50 kΩ
1 kΩ1 kΩ
x1
x10
x100
x1000
x1
x10
HB
HB
OFFSET
DAC Phase
adjustment
±90 °
Sine generator
0.6 to 20 kHz
Single
master Crystal
oszillator
PLL
REF
Slave
Master
2.5 VRMS
CLK
EXC+
SENSE+
R+
IN+
IN-
SENSE-
EXC-
TEDS
GND
7th order
reconstruc-
tion  lter
0.48 x fc
2nd order
lowpass  lter
10 Hz to 3 kHz,
OFF
} }
Quarter bridge completion Shunt
INPUT
CONNECTOR
OUTPUT
CONNECTOR
9-pin DSUB 9-pin DSUB
1 8
6
5
2
1
7
3
8
9
4
SYNC
IN / OUT
OUT
DAQP-CFB2
Apply shunt: Press the FILTER button for more than 3 seconds to apply the internal shunt
resistor as long as you keep the button pressed.
Apply Zero ref.: Press the RANGE button for more than 3 seconds to shortcurcuit the module input
as long as you keep the button pressed.
Amplier balance: Press the RANGE button for more than 3 seconds (zero reference). Keep the
RANGE button pressed and push the FILTER button in addition. This will set
the module o󰀨set to zero. The calibration values will be stored in the module!
This function is independent from the sensor and takes approx. 2 seconds!
Sensor balance: Press both RANGE and FILTER button together for more than 2 seconds.
This will set the o󰀨set of a connected sensor to zero. The sensor o󰀨set
correction is working within ±400 % of full scale range.
Factory default: Press both RANGE and FILTER button at power up for approx. 3 seconds to
set the amplier to factory default settings (full bridge, 100 mV/V, 5 VRMS,
Bessel, module address 0x00, 100 kΩ shunt, power-on-default o󰀨,
manual control).
Free variable gain and offset
The programmable gain amplier (PGA) combined with the variable gain amplier (VGA) allow a wide input
gain from 0.1 mV/V to 1000 mV/V. The o󰀨set is free programmable between ±400 % of the input with a
resolution of 17 bit. So it is possible to normalize almost any sensor signal to the ±5 V amplier output.
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

12
DAQP-CFB2
Excitation Voltage
The excitation voltage is programmable to 1, 2 or 5 V. The carrier frequency is programmable to 0.6,1, 2.5,
3, 5, 10 or 20 kHz. When the module is congured as “stand alone” or as “single” the frequency is based on
a crystal oscillator. When it is switched to external clock a PLL synchronizes the excitation with the external
signal. The EXC+ and EXC- voltage is always balanced around GND. That allows using the ground potential
as shield. For high accuracy strain gage measurement it is recommended using lower frequencies. When
higher bandwidth is required use higher carrier frequencies.
Remote Sense
The DAQP-CFB2 supports remote sense. That means that the excitation voltage loss in the sensor cable is
compensated. The sense line terminals are internally connected to the excitation via a 100 kΩ resistor. For
accurate voltage regulation there has to be also an external connection. Even if the remote sense function is
not required. Sense has to be connected to EXC.
Phase adjustment
In inductive mode the phase of the amplier needs to be adjusted to compensate the phase shift due to
sensor and wiring. The DAQP-CFB2 is able to compensate ±90° with the phase sensitive rectier.
Output offset
The output o󰀨set can be programmed from positive to negative full scale range. This is useful if the DAQP-
CFB2 is used as an analog signal conditioner.
Input offset
The input o󰀨set can be set ±400 % of the input range. It is automatically recalculated when changing the
measurement range. The input o󰀨set is automatically determined with the sensor balance function.
Internal Completion Resistors
The DAQP-CFB2 has internal half bridge completion and internal quarter bridge completion wiring for
120 Ω and 350 Ω strain gages. High precision resistors with low temperature drift allow a long-term stable
measurement of almost every strain gage type without using an external completion network.
Internal Shunt
A 50 kΩ and a 100 kΩ shunt resistor can be applied to the bridge internally. This is called “shunt calibration”.
With this technique the whole measurement chain (sensor, amplier and analog-to-digital conversion) can be
checked. The table below shows the shunt calibration results for typical strain gage resistance values.
Strain gage Resistor Shunt resistor Result
120 Ω 50 kΩ 0.6 mV/V
120 Ω 100 kΩ 0.3 mV/V
350 Ω 50 kΩ 1.74 mV/V
350 Ω 100 kΩ 0.87 mV/V
The shunt resistor check is not possible in inductive bridge operation mode.
Amplifier balance
Balance amplier allows eliminating all internal amplier o󰀨sets automatically. It switches the di󰀨erential
amplier inputs IN+ and IN- to internal GND. Then the output o󰀨set of the module is adjusted to zero for all
ranges. This function takes up to 8 seconds. Previously stored sensor o󰀨set values are cleared.

13
DAQP-CFB2
Sensor Balance
Typically every strain gage sensor has a certain o󰀨set. This arises from manufacturing tolerances or from
sensor mounting. By performing a sensor balance the sensor o󰀨set can be removed on the analog side up
to 400 % of the actual range. This allows using the full range of the AD board instead of losing resolution
because of digital o󰀨set shifting. The maximum adjustable o󰀨set is mentioned in the range overview table.
The sensor o󰀨set is stored in the module and is recalculated automatically when changing the range.
Short
It switches the di󰀨erential amplier inputs IN+ and IN- to internal GND. With this function the absolute sensor
o󰀨set can be determined.
Cal
Independently from the input signal this function sets the output to 80 % of the actual range. The calibration
signal is based on the excitation voltage. So this is a simple check of the excitation voltage. Typical reason
why the excitation is not working are short circuit of the excitation at the cabling or sensor defects, too
high load for the excitation amplier (please decrease the excitation voltage) or incorrect setting of the
synchronisation mode (no master assigned).
Filter
The DAQP-CFB has two lters. The rst is a 7th order Butterworth lter for signal reconstruction. The cut o󰀨
frequency of this lter is automatically 0.48* carrier frequency. The second lter stage is a programmable 2nd
order lter. The characteristic can be chosen between Bessel and Butterworth. This lter is compatible to
most other DAQP series modules. OFF-mode means bypassing the 2nd order lter.
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14
DAQP-CFB2
DAQP-CFB2 Step Response
The 7th order Butterworth  ler has an overshoot of 14 % in time domain. Bessel  lters do not have any
overshoot.
Synchronizing multiple amplifiers
The high ampli cation of strain gage ampli ers requires to synchronize the excitation voltage if multiple
channels are used. This is done with pin 8 of the back plane connector. When mixing DAQP-CFB and
DAQP-CFB2 modules please consider that the DAQP-CFB ampli er only support 5 kHz excitation.
The DAQP-CFB2 o󰀨 ers three synchronisation modes:
Single: DAQP-CFB2 uses the internal crystal oscillator and outputs no synch signal.
Master: DAQP-CFB2 uses the internal crystal oscillator and serves a synch signal.
Slave: DAQP-CFB2 synchronises the excitation voltage to the synchronisation signal. No sync
ampli er is required anymore when DAQP-CFB2 is used in slave mode. When switching into
slave mode the frequency is auto detected and cannot be changed anymore.
Sync of up to 16 channels:
Synchronisation of the carrier frequency is required when:
Sensor cables of di󰀨 erent CFBs are nearby
Sensors are mounted on the same metal structure (capacitive signal coupling)
No synchronisation is required when:
Isolated sensors are on non-conductive structures
For ranges above 100 mV/V because of the low ampli cation and therefore less in uence of crosstalk
between wires and cables.
In some special DEWETRON Racks pin 8 is already in use for customized sensor supply voltage level. If
so, only single mode operation is possible.
Master SlaveSlaveSlaveSlave
Pin 8
. . .
Module 4
Module 3 Module 2 Module 1 Module 0 Module 15

15
DAQP-CFB2
Bridge mode accuracy
Excitation 1 VRMS 2 VRMS 5 VRMS
Input ranges
Amplier gain mv/V mv/V mv/V Accuracy
5 1000 500 200 0.1% of reading ±0.05% of range
10 500 100 0.1% of reading ±0.05% of range
12.5 200 0.1% of reading ±0.05% of range
20 50 0.1% of reading ±0.05% of range
25 200 100 0.1% of reading ±0.05% of range
50 100 50 20 0.1% of reading ±0.05% of range
100 50 10 0.1% of reading ±0.05% of range
125 20 0.1% of reading ±0.05% of range
200 5 0.1% of reading ±0.05% of range
250 20 10 0.1% of reading ±0.05% of range
500 10 5 2 0.1% of reading ±0.05% of range
1000 5 1 0.1% of reading ±0.05% of range
1250 2 0.1% of reading ±0.05% of range
2000 0.5 0.1% of reading ±0.05% of range
2500 2 1 0.1% of reading ±0.05% of range
5000 1 0.5 0.2 0.1% of reading ±0.05% of range
10000 0.5 0.1 0.2% of reading ±0.2uV/V*
12500 0.2 0.2% of reading ±0.2uV/V*
25000 0.2 0.1 0.2% of reading ±0.2uV/V*
*) only specied for 5 kHz excitation frequency.
Signal connection
1 EXC+
2 IN+
3 SENSE -
4 GND
5 R+ / Shunt
6 SENSE+
7 IN-
8 EXC-
9 TEDS
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

16
DAQP-CFB2
EXC+
Sense+
R+
1)
IN+
Sense-
EXC-
IN-
Shield
1
6
5
2
3
8
7
4
9-pin SUB-D
TEDS
GND
9
4
TEDS
Data
GND
1
5
7
3
6
2
4
H
8-pin LEMO
8
H
Full bridge signal connection
6-wire and 4-wire sensor connection
Voltage or current excitation is allowed.
Sense terminals have to be connected to excitation also when 4-wire connection is used.
4-wire connection
6-wire connection
EXC+
Sense+
R+
1)
IN+
Sense-
EXC-
Shield
1
6
5
2
3
8
9-pin SUB-D
4
TEDS
GND
9
4
TEDS
Data
GND
Potentiometric Sensor
200 Ohm to 10 kOhm
Half bridge signal connection
5-wire and 3-wire sensor connection, potentiometric sensors
Sense terminals have to be connected to excitation also when 4-wire connection is used.
A potentiometer works like a half bridge sensor with ±500 mV/V sensitivity. The scaling is:
0 % position equals -500 mV
100 % position equals +500 mV
3-wire connection
5-wire connection
1) 'R+' has to be connected only if shunt check is required, otherwise it can be left unconnected.

17
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printi ng version 2.3.4 • November 18, 2020
DAQP-CFB2
EXC+
Sense+
R+
IN+
Sense-
EXC-
Shield
TEDS
GND TEDS
Data
GND
1
6
5
2
3
8
9-pin SUB-D
4
9
4
Sense leads (D-SUB: pin 3 and 6) have to be connected!
3-wire sensor connection
(Sense+ is connected to EXC+ at the connector)
Quarter bridge signal connection
Inductive bridge sensors (LVDT)
Inductive half-bridge sensors
3-wire quarter bridge is only able to compensate symmetric wire resistance!
Linear Variable Differential Transformers
Sense+
Sense+
Sense-
Sense-
EXC-
EXC-
IN+
IN+
GND
EXC+
EXC+
1
1
6
6
2
2
4
3
3
8
8
Displacement sensors
Pressure sensors
Connectors
Connectors
Core
Core
2-wire connection
2-wire connection
4-wire connection
4-wire connection

18
DAQP-CFB2
Capacitance measurement
Capacitance measurement of the DAQP-CFB2 works with the following technology. It applies a determined
excitation AC voltage with 5 kHz to the capacitor. The module measures the current through the capacitor
by using the 120 Ω completion resistor as a shunt. Depending of the unknown impedance, this current is
phase shifted to the excitation voltage. The 90° component of this current is proportional to the unknown
capacitance. Only this component is amplied and rectied.
Sense+ Sense+
Sense- Sense-
GND
EXC- EXC-
IN- IN-
IN+ IN+
R+ R+
EXC+ EXC+
1
6
5
2
7
3
8
Connectors Connectors
Cx
Cx
RG174
Capacitors of
10 to 1000 nF
Capacitors of
20pF to 10nF
2-wire connection
4-wire connection
1
6
5
2
7
4
3
8
Sensor connection:
4-wire connection only makes sense for the ranges from 10 nF to 1 µF. For ranges below 10 nF use two
shielded cables for the measurement leads to avoid measuring parasitic capacitances.
Connect shield to pin 4 (GND).
Measuring small capacitances:
To improve measurement accuracy of small capacitances, perform a sensor balance with the test leads open
to subtract the residual capacitance of the DAQP-CFB2 and the leads.
CAUTION: To avoid possible damage to the DAQP-CFB, disconnect circuit power and discharge all
high-voltage capacitors before measuring capacitance.
Capacitance measurement accuracy
Range Excitation voltage DC accuracy
[nF] [VRMS]
1000 0.25 1 nF±0.3 % of reading
500 0.25 500 pF ±0.3 % of reading
200 0.25 200 pF ±0.3 % of reading
100 0.25 100 pF ±0.3 % of reading
50 4 50 pF ±0.3 % of reading
10 5 10 pF ±0.3 % of reading
5 5 5 pF ±0.3 % of reading
1 5 1 pF ±0.3 % of reading
0.5 5 0.5 pF ±0.3 % of reading
0.2 5 0.2 pF ±0.3 % of reading
0.1 5 0.2 pF±0.3 % of reading
0.05 5 0.2 pF ±0.3 % of reading
0.02 5 0.2 pF ±0.3 % of reading
!

19
DAQP-CFB2
Why use more wire technology
Sensitivity: For sensor wiring typically copper cables are used. For example a 120 Ω full bridge
connected with a 4 x 0.14 mm2 cable will have an sensitivity error of 2.1 % just because of the 1.27 Ω
wire resistance. By using the 6 wire technology, this can be completely compensated.
Temperature drift: Copper has a temperature drift of 0.4 % /°C.This is especially a problem at quarter
bridges, because also the o󰀨set changes with the wire resistance. The following table shows the
di󰀨erence between the 3 wiring methods for a 120 Ω strain gage with a 50 m cable 0.25 mm2.
Initial error Drift because of 10 °C warm-up
O󰀨set Sensitivity O󰀨set Sensitivity
2-wire 25183 µm/m -4,97 % 956 µm/m -0.18 %
3-wire 0 µm/m -2.6 % 0 µm/m -0.01 %
Cables
To keep the inuence of electromagnetic disturbances as small as possible shielded twisted pair cables are
strongly recommended. Connect the shield to the GND or the housing (pin 4).
The twisted pairs for all bridge modes are:
EXC+ PIN1 and EXC- PIN8
Sense+ PIN6 and Sense- PIN3
IN+ PIN2 and In – PIN7
R + PIN5 and GNDisolated PIN4
For quarter bridge mode the pairs are:
IN+ PIN2 and Sense – PIN3
R + PIN5 and EXC- Pin8
If TEDS is used it is recommended mounting the TEDS chip nearby the module. The ideal case would be if
the chip is mounted inside the D-SUB housing. The maximum distance between modules and TEDS chip is
20 m.
450134 • DAQP/HSI/PAD Modules • Technical Reference Manual • Printing version 2.3.4 • November 18, 2020

20
DAQP-CFB2
Notes