ALTHEN SG-KP Series User manual

Single Channel Strain Gauge Amplifier
SG-KP-12E/24E-xxx
Germany | Switzerlan | Austria
Althen GmbH Mess- & Sensortechnik
Tel: + 49 (0)619 - 70060
[email protected]
Benelux
Althen bv Sensors & Controls
Tel: [phone]
[email protected]
France
Althen / DB Innovation
Tél : [phone]
[email protected]
Swe en
Althen Sensors & Control AB
Tel. [phone]
[email protected]
USA | Cana a
Altheris Inc Sensors & Controls Inc.
Tel: [phone]
[email protected]
Other Countries
please contact us
by email at
[email protected]
www.althen.de
V2.1
eng

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Content
1 General Information 3
1.1 Safety Instructions 3
1.2 Qualified Personnel 3
1.3 Intended Use 3
2 Instructions for use of the measuring amplifier 4
2.1 Instructions for use of strain gauge sensors
3 Technical description
4 Terminal Assignment 6
4.1 Supply voltage 7
4.1.1 Galvanic isolation 7
4.2 Strain gauge excitation voltage 7
4.2.1 Connecting in 4 or 6 wire technology 8
4.2.2 Connecting in 4 wire technology 8
4.2.3 Lenghening a cable in 4 wire technology 9
4.2.4 Connecting in 6 wire technology 10
4.3 Analogue output 10
4.3.1 Analogue output voltage 11
4.3.2 Analogue output current 11
4.3.3 Low-pass filter 11
 Startign up 12
 .1 Zero point adjustment range 12
 .2 Adjustment / calibration of the amplifier 13
 .2.1 Correction of the analogue current output 14
 .2.2 Calculation of amplification determing resistor 14
6 Maintenence 1
7 Old appliances disposal 1
Appendix 16
Datasheet 16
Order designation 16
Component diagram 17
Housing dimensions 18

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1 General Information
To ensure reliable and safe operation, the measuring amplifier must be operated in compliance with
the specifications according to this technical description only. These regulations must also be
observed if using accessories, that have been ordered from Althen Mess- & Sensortechnik GmbH
together with the measuring amplifier.
Notice: Every person who is in charge for the start-up or service of this measuring amplifier must
have read this technical manual and must have understood the safety instructions in particular.
1.1 Safety Instructions
When using the amplifier, the legal- and safety regulations for each case of application must be
observed. To avoid risks for the system or the operator the following points are to be considered.
■ If any visual damage or malfunctions are noticed, the measuring system must be switched
off and marked appropriately.
■ Disconnect the supply voltage before opening the device.
■ The complete measuring unit must be protected against contact and influence of
unauthorized persons.
■ In the case of a safety-relevant application, where a potential malfunction could cause
damage to property or persons, it is imperative that an additional, independent monitor is
provided.
■ In combination with sensors, the maximum loads / pressures etc. must never be
exceeded.
If you have reasons to assume that safe operation is no longer possible, immediately take the device
out of operation and secure it against unintentional operation.
1.2 Qualifie Personnel
This measuring system must be operated by qualified personnel and in compliance with the relevant
technical specifications only. Qualified personnel include such persons who are conversant with the
setting up, mounting and starting up of the measuring system and who have qualifications that are
appropriate for the tasks they're about to perform.
1.3 Inten e Use
Amplifiers from Althen Mess- & Sensortechnik GmbH serve to measure the intended measurand and
the evaluation thereof in combination with one or more sensors. Any other use over and above that is
regarded as non-intended use.

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2 Instructions for use of the measuring amplifier
Notice: The parameterizations, further information concerning the scaling as well as the customized
analogue output can be found on the additional sheet "Device-Configuration".
Since this amplifier is a highly sensitive measurement technology
product, it must be used for its intended use as well as the
described operating conditions only. Initial start-up and changes in
setup and settings must be done by qualified personnel only. To
prevent interventions / modifications made by unauthorized
personnel, suitable measures must be taken. Both function and
calibration must be checked regularly.
Notice: To avoid possible interferences, it is recommended to
install the amplifier with at least 20 mm distance to other
electronic devices.
The amplifier is contained in a plastic housing (IP20) designed for
DIN top hat rail montage. The electrical connections are made via
screw-clamps and the sensor may be connected in 4 or 6-wire technology.
The amplifier must be connected to clean earth-potential. To avoid possible potential equalization
currents over the shield of the cable to the following evaluation unit, this shield should be connected
over a suitable capacitor (10nF/200V).
Overall the shield connections must be done properly to EMC-
standards (as short as possible with large wire cross-section)
and connected to a central point (star grounding). In order to
not increase the interference sensitivity of the amplifier, all
cables should be kept as short as possible and should not be
extended. Possible cable-bound interferences must be blocked
very near the cable ends (evaluation unit) by suitable
measures.
To increase immunity to interferences (i.e. noise) the wiring
must be put through the delivered ferrites. Shielded cables,
preferably twisted in pairs should be used only. The EMC-
installation instructions must be complied with. All connection
cables and the amplifier must not be installed in proximity to disturbance emitting devices or cables.
The amplifier must be operated with a separate power source used for measurement devices only.
Notice: Changes of the amplifier of any kind demand for the explicit approval of Althen Mess- &
Sensortechnik GmbH. Changes of any kind done without that approval exclude all possible warranty
and/or liability of Althen Mess- & Sensortechnik GmbH.

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2.1 Instructions for use of strain gauge sensors
Notice: Strain gauge sensors with a small range are extremely sensitive to improper handling. Force
transducers can be destroyed simply by touching. Same applies to the diaphragms of pressure
transducers. So, bear in mind: handle with care!
Loading the transducer in excess of the nominal range may result in an increased and lasting zero
balance offset as well as damage to the sensor. The same applies to short-term force or pressure
impulses that exceed the nominal range.
To most force transducers the force must be applied centrically in order to avoid shear forces, which
may be harmful to the sensor, or may cause measurement inaccuracy. Rounded surfaces, joint heads
or other suitable guides can ensure centric force transmission.
Tightening torques while mounting any sensors may result in an increased zero balance offset.
If the sensor has been replaced, the calibration of the amplifier must be checked. A new adjustment
might be necessary.
3 Technical escription
The described single channel measuring amplifier serves to supply a strain gauge sensor with a full
bridge resistance of 300 Ohms or more and the amplification of the sensor signal. The supply voltage
of the amplifier is galvanically isolated from analogue output, sensor supply and sensor signal.
Standard analogue outputs are available for further evaluation.
The coarse amplification is determined by an internal resistor and can be fine adjusted by a
potentiometer on front of the amplifier. A second potentiometer on front allows the correction of the
zero point.
The presence of the supply / internal operating voltage is indicated by the 2 green LEDs on the front.

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4 Terminal Assignment
The electrical connections are made via screw-clamps. The numbering can be found on the front side
of the clamps. The maximum wire cross section is 2, mm². The EMC-installation instruction is to be
complied with. Maximum interference immunity is achieved by direct connection of the cable screen
with “clean” and low resistance protective ground (PG). A lengthening of the cable screen makes the
interference immunity considerably worse. The connection of the screen should be done directly with a
cable clamp.
If, however, a connection to a PG is not possible, the cable screen may be connected to clamp 1 of the
amplifier (analogue ground/screen). Anyhow, enough interference immunity is to be ensured.
Clamp
Description
Clamp
Description
1
Supply voltage 9 -SG-Signal Transducer
2
Supply Ground
10
+SG
-
Signal Transducer
3
Supply Ground 11 +SG-Sense Transducer
4
Analogue Ground 12 +SG-Excitation Transducer
Analogue Ground 13 -SG-Sense Transducer
6
Analogue output 2 (Version 4 … 20 mA)
14
-SG-Excitation Transducer
7
Analogue Ground
1
Analogue Ground/Screen
8
Analogue output 1 (0 … +10 V / ± 10 V)
16
Analogue Ground
Terminals “supply ground” and “analogue ground” are isolated galvanically. To unset this isolation
clamp 3 and 4 are to be bridged.
4/6 wire technology:
Factory pre-set
Jumper J1 Jumper J2
* 4-wire technology ON ON
6-wire technology OFF OFF

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4.1 Supply voltage
The supply voltage of version -24E is in the range of 18 to 30 VDC and version –E12 within 10 to 18
VDC. The presence of the supply / internal operating voltage is indicated by the 2 green LEDs on the
front.
To protect the electronics (to the supply voltage version corresponding) an internal self-healing
“polyswitch-resettable®” fuse is built in. Whether an external additional fuse is necessary has to be
considered. However, an additional external delay fuse of 0,31 A is recommended.
If the indicator LEDs go off, the supply voltage and possibly existing external protection has to be
checked.
Notice: During switch-on phase the amplifier is capacitive. Thus, the switch-on current is greater than
the operating current. This must be taken into consideration when dimensioning and selecting the
power pack, especially if several amplifiers are being wired to the same power source.
4.1.1 Galvanic isolation
The supply voltage of the amplifier is galvanically isolated from analogue output, sensor supply and
sensor signal. To unset this isolation, clamp 3 and 4 have to be bridged.
4.2 Strain gauge excitation voltage
The described measuring amplifier is able to supply one strain gauge transducer. Any strain gauge full
bridge with a bridge resistance of 300 Ohms or more may be connected. The transducer can be
supplied with a bipolar voltage of either ± V (= 10 V) or ± 2, V (= V). This value can be selected by
internal solder points and with 2 potentiometers for fine adjustment.
LP81-1 LP81-2 SG-Excitation
SET SET ± VDC (=10VDC)
NOT SET NOT SET ±2, VDC (= VDC)

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4.2.1 Connecting in 4 or 6 wire technology
The described measuring amplifier allows to connect the transducer in either 4 or 6 wire technology.
The excitation voltage received by the sensor has great influence on the sensors signal. So, if with a
very long cable, or lengthening of it, the excitation voltage drops even by a slight value the signal drops
accordingly. If the amplifier together with the sensor has been factory calibrated a longer cable is not a
problem. But it must not be lengthened. This way the factory calibration is still valid.
It is preferred to connect the sensor in 6 wire technology, if the cable has to be lengthened, because
the 2 additional wires measure the excitation voltage directly at the sensor and the amplifier adjusts
the excitation voltage accordingly.
4.2.2 Connecting in 4 wire technology
Notice: When connecting in 4 wire technology the jumpers J1 and J2 must be set. Otherwise the
transducer might get damaged resp. destroyed.
The values in the calibration certificate of the sensor have been recorded with the attached cable. So,
this cable must not be shortened, because it would increase the sensor signal and therefore change
the accuracy.
With a sensor without a cable the values of the certificate have been recorded right at the connector. In this case
a connection in 6 wire technology is recommended.
Pic. 1: Connection in 4-wire technology
SG-Amplifier
SG-Signal
Internal jumpers
J1 and J2
+Sense
+SG-Excitation
-Sense
-SG-Excitation
Transducer cable
3 0 Ohm

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4.2.3 Lenghening a cable in 4 wire technology
As mentioned above the connection should be in 6 wire technology if the sensor comes with no hard-
mounted cable or the existing cable is to be lengthened.
Example: The sensor has been calibrated with an excitation of 10,000 V.
Pic. 2: Connection in 4-wire technology; drop of SG-Excitation voltage caused by cable lengthening (0, Ohm)
In the picture above the original cable has been lengthened and this additional cable results in a
resistance increasing of 0, ohms. Thus, the excitation voltage drops by 0,03 V (resp. 30 mV) which
results a measurement inaccuracy of 0,3 %.
Pic. 3: Sensor with 4 wire cable. Lengthened with 6 wire cable
In the picture above the cable has been lengthened with a 6-wire cable, so the voltage drop of 30 mV
is corrected by the amplifier by measuring the actual voltage at the end of the original cable.
SG-Amplifier
SG-Signal
SG-Excitation voltage
9,97 V
+Sense
+SG-Excitation
-Sense
-SG-Excitation
Transducer cable
SG-Excitation voltage
10,00 V
R wire=0, Ohm
R wire=0, Ohm
3 0 Ohm
Cable lengthening
SG-Amplifier
SG-Signal
SG-Exctiation voltage
10,00 V
+Sense
+SG-Excitation
-Sense
-SG-Excitation
Transducer cable
SG-Excitation voltage
10,03 V
3 0 Ohm
R wire=0, Ohm

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4.2.4 Connecting in 6 wire technology
Notice: When connecting in 6 wire technology the jumpers J1 and J2 must be removed. Otherwise the
6-wire technology does not have the desired effect.
Pic. 4: Connection in 6-wire technology
4.3 Analogue output
The following standardized analogue outputs, depending on the ordered option, are available:
Version …010:
The output is: 0 … +10 Volts (max 1 mA)
Version …B10:
The output is: ± 10 Volts (max 1 mA)
Version …420:
The output is: 4 … 20 mA (max 00 ohms)
Other analogue outputs available on request. For parameter settings, further information concerning
scaling, or customized analogue outputs, please refer to the additional sheet “Allocation / Device
Configuration).
SG-Amplifier
SG-Signal
+Sense
+SG-Excitation
-Sense
-SG-Excitation
Transducer cable
3 0 Ohm
R
wire=0, Ohm
R
wire=0, Ohm

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4.3.1 Analogue output voltage
The analogue voltage output can be picked up on the corresponding clamps. See chapter 4 “Terminal
Assignment”.
In combination with a transducer which is capable to handle tension and compression forces an
analogue output of ± 10 volts is available. If an unipolar voltage is needed with such a sensor it is
possible to set the zero point of the transducer to volts of the output. This zero-point elevation is also
necessary for the analogue current output. See chapter .1
4.3.2 Analogue output current
The analogue current output can be picked up on the corresponding clamps. See chapter 4 “Terminal
Assignment”:
The analogue current output is not capable of going below 4 mA, therefore when adjusting the
designated zero-point, the output signal has to be set slightly higher than that, just in order to check if
said signal does not virtually hang below 4 mA. If the output reacts immediately it can be set back to
4 mA, otherwise the signal of the transducer has to be checked. If the current of 4 mA does not
increase while loading a force to the transducer the polarity of the signal has to be checked. If this is of
negative polarity the signal wires need to be interchanged.
If the circuit of the analogue current output is open somehow, this is indicated by a red LED on the
front.
4.3.3 Low-pass filter
In order to suppress unwanted high frequency disturbances a low pass filter can be switched on. The
DIP-switches have to be set accordingly:
Frequency Limit DIP60/4 DIP60/3
10 Hz (Lowpass Filter) OFF ON
1 kHz ON OFF
Notice: Low-pass filter is not factory preset.
If an optional higher limit frequency has been ordered, the low-pass filter will be set from
10Hz to 1kHz.
Before removing the pcb from its casing, the grounded hat-rail is to be touched.

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5 Starting up
If an adjustment (A-K-1K / A-D-1K) has been ordered in combination with the amplifier(-s) and/or
transducers(-s) it may be necessary for a slight fine adjustment nonetheless. This is due to possible
various environmental influences as well as to mounting etc.
If any visual damage or malfunctions are noticed, the measuring system must be switched off and
marked appropriately.
■ Mounting transducer and amplifier
■ Connect transducer to the amplifier
■ Connect multimeter to analogue output
■ Connect supply voltage – consider pin assignment
■ Allow the system about 30 min. to warm up
■ Check function and calibration of the system
Notice: The allocation of transducer / amplifier is to be complied with. After replacing a transducer,
the calibration has to be checked. It is to be noted that there is a slight dependence between zero-
point adjustment and amplification (gain).
5.1 Zero point a justment range
It is to be noted that there is a slight dependence between zero-point adjustment and amplification
(gain).
The zero-point adjustment range is approx. ± 10 %.
This range can be changed by setting the dip-switch according to the table below:
Setting the zero point:
Increase DIP60/2 DIP60/1
+ V OFF ON
- V ON OFF
Notice: A base load reduces the remaining load capacity by just that value. Overloading may cause
damage!
Base load / tare + maximum load to measure = capacity of transducer
DIP 0-1 DIP 0-2 DIP 0-3 DIP 0-4 corresponding to the analogue voltage output
ON ON ON ON -1,0 V … +1,0 V
ON OFF OFF ON -3,3 V … +3,3 V
ON OFF ON OFF +0,4 V … +4,0 V
OFF ON OFF ON -4,0 V … -0,4 V

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5.2 A justment / calibration of the amplifier
In order to adjust or calibrate the amplifier a multimeter has to be connected to the analogue output.
Inspection:
■ Unload the measuring device.
■ Connect the multimeter (refer to chapter 4 “Terminal Assignment”).
■ Set the analogue output to 0 Volts resp. 4 mA.
■ Load the measuring device (i.e. the transducer) at least 3 times with its maximum load.
■ Load the device with 80 % of its maximum load.
■ Check if the analogue outputs comply with the load and is in the designated specs.
■ If not, the measurement system might need to be recalibrated. Above that, the installation
position and the overall setup might need an inspection.
Adjustment / Calibration:
The coarse amplification, and thus the voltage output, is determined by an internal resistor (RG) and
can be fine adjusted by a potentiometer (P-02). To adjust the current output, which follows the voltage
output, the potentiometer P-03 is to be used. (See next chapter.)
Before the calibration a warm-up time of approx. 30 mins should be kept. The measuring device has to
be unloaded.
Unloaded means with:
■ Force transducers: no applied force at all
■ Pressure transducers no pressure, except atmospheric influence
■ In this unloaded state adjust the zero-point with the potentiometer P-01.
■ Apply a defined load. (by calibrated weights, pressure generator etc.)
■ Adjust the analogue output corresponding to the applied load.
In order to reach the required accuracy, it may be necessary to repeat these steps.

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5.2.1 Correction of the analogue current output
The minimum of analogue current output is 4 mA. A lower current is not possible. When calibrating, the
zero-point current has to be set to 4,1 mA with the potentiometer “NULLPUNKT”. Now the range of the
current output can be set to 16 mA by using the potentiometer P-03. With an adjusted range of 16 mA
the output has to read 20,1 mA at maximum load. After adjusting the range, the zero shall be set back
to 4,0 mA.
5.2.2 Calculation of amplification eterming resistor
The amplification is:
G total = G differential amplifier x G output stage
The amplification of the output stage is adjustable with the potentiometer P-02 (GAIN). The adjustable
range is:
G output stage = 9, … 10, Volts
Calculation of the coarse amplification resistor R G (applies for 10 Volts output):
G differential amplifier =
1000 mV
Exc. (V) x Signal (
mV
V
)
R G =
0 kOhm
(G differential amplifier –1)
Example:
Transducer: 2, 000 mV/V (0,002 V/V)
Excitation: 10,000 V
R G =
0 kOhm
(
1V
10 V x 0,002 V
-1)
= 1282 Ohm

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6 Maintenence
The flawless function and calibration of the whole measuring system is to be checked regularly. This
inspection is also necessary after every repair or change of any component of the measurement
system.
7 Ol appliances isposal
According to European and German law, it is prohibited to dispose old electronic
devices into household waste, but must be collected and disposed of separately.
Amplifiers and measurement units manufactured and sold by Althen Mess- & Sensortechnik GmbH
serve B2B purposes only. Therefore, those old appliances must not be given to the communal disposer,
but must be given back to the seller or disposed of properly. If you need any further information, please
contact your local authorities.
These measures serve to protect the environment and allow recycling and recovery of valuable
materials. Furthermore, do electronic devices contain substances that may cause damage to the
environment if burned or dumped with normal household waste.

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Appen ix
Datasheet
Number of measuring channels: 1 (Strain gauge full bridge > 300 Ω)
Supply voltage: 12E - 10 … 18 VDC
24E - 18 … 30 VDC Electronics protected against voltage reversal
Isolating proof voltage input to output: 200 V Higher isolated proof voltage on request
Power consumption: max. 3 W
Strain gauge excitation supply: ±2, VDC ± 1% / ± VDC ± 1%
Analogue output 0 … 10 V / ±10 V
4 … 20 mA
max. 1 mA (short-period short-circuit proof)
max. 00 Ω
Limit frequency (-3 dB): 1 kHz (10 Hz with low pass filter) optional up to 30 kHz
Input resistance: >3 MΩ
Max. input sensitivity: 100 mV/V at ± VDC excitation supply
Non-linearity: ±0.0 % FSO
Electrical connection: Pluggable Screw clamps
Housing: Plastic enclosure for top hat rail mounting (IP20)
Dimension (W x H x D): 23 x 99 x 11 mm
Weight: approx. 1 0 g
Temperature, storage: -20 °C … +60 °C
Temperature, operating: 0 °C … + 0 °C
Or er esignation
SG
-
KP…
Single channel strain gauge
-
amplifier in plastic housing for DIN
-
top hat
rail mounting
(IP20)
…-12E-… Supply voltage: 10 … 18 VDC
…
-
24E
-
…
Supply voltage: 18 … 30 VDC
…-010-… Analogue output: 0 … 10 V
…-B10-… Analogue output: ± 10 V
…
-
420
-
…
Analogue output: 0 … 10 V and 4 … 20 mA
… -GFxxx frequency limit up to 30 kHz
…no declaration standard version 1 kHz

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Component iagram
DIP
-
50
Zero Point
-
Range
DIP
-
60
1+2: Increase Signal
3+4: Low-pass- ilter
4 1 4
LP81
-
1
SG-Exc.
voltage
LP81
-
2
SG-Exc.
voltage
Rg (R3); Visible
a ter removing
the EMC-plate

18 | 18
Housing imensions
Subject to modifications.
All information describes our products in general form.