MSI - LVDT
LVDT signal conditioning
Technical Reference Manual
v 1.0
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MSI - LVDT
Table of Contents
1
Theory of operation ........................................................................................................................................ 3
2
Technical data ................................................................................................................................................. 4
2.1
Electrical specifications.......................................................................................................................... 4
2.2
Connectors............................................................................................................................................. 5
2.2.1
Input connector pinout ..................................................................................................................... 5
2.2.2
Output connector pinout .................................................................................................................. 5
2.3
3
Operation............................................................................................................................................... 6
2.3.3
Connections ....................................................................................................................................... 6
2.3.4
MSI adapters / TEDS sensor support ................................................................................................. 7
Documentation Version .................................................................................................................................. 9
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MSI - LVDT
1
Theory of operation
The MSI – LVDT Adapter is a complete Linear Variable Differential Transformer (LVDT) signal conditioning
subsystem. It is used in conjunction with LVDTs to convert transducer mechanical position to a unipolar dc
voltage with a high degree of accuracy and repeatability.
LVDTs are robust, absolute linear position/displacement transducers; inherently frictionless,
they have a virtually infinite cycle life when properly used. As AC operated LVDTs do not
contain any electronics, they can be designed to operate at cryogenic temperatures or up
to 1200°F (650°C), in harsh environments, under high vibration and shock levels. LVDTs have
been widely used in applications such as power turbines, hydraulics, automation, aircraft,
satellites, nuclear reactors, and many others.
The LVDT converts a position or linear displacement from a mechanical reference (zero, or null position) into a
proportional electrical signal containing phase (for direction) and amplitude (for distance) information. The LVDT
operation does not require an electrical contact between the moving part (probe or core assembly) and the coil
assembly, but instead relies on electromagnetic coupling.
FUNCTIONAL BLOCK DIAGRAM
MSI - LVDT Adapter uses a unique ratiometric architecture to eliminate several of the disadvantages associated
with traditional approaches to LVDT interfacing. The benefits of this new circuit are: no adjustments are
necessary; temperature stability is improved; and transducer interchangeability is improved.
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MSI - LVDT
2
Technical data
2.1
Electrical specifications
MSI - LVDT adapter is powered by EXC voltage. LVDT adapter is compatible with SIRIUS(i) (variable EXC) or
DEWE 43A type instrument (fixed +/-5V EXC).
Power supply Exc. Voltage
10V – 15V, from EXC+ to EXC- outputs
Power supply Exc. Current
44mA, from EXC+ to EXC- outputs (1)
Output voltage
1,00V (2)
Gain error
1% of Full Scale
Output TCR
55ppm/K of Full Scale
Sensor VTR = S x d, Sensitivity
2000mV/V maximum
Sensor supported type
Differential LVDR or RVDT, Inductive Half-Bridge LVDT
Sensor Exc. voltage
2,88Vrms (differential) (3)
Sensor Exc. frequency
Selectable 4,02kHz / 9,60kHz typical; 2,5% error
Phase compensation
-50º to +85º at 4kHz; -75º to +70º at 10kHz.
TEDS
1024-Bit, 1-Wire EEPROM (4)
Table 1: Electrical specifications
(1)
(2)
(3)
(4)
Absolute maximum rating, specified for SIRIUSi.
For sensor VTR (Voltage Transfer Ratio) = 1000mV/V.
Sinusoidal, 50dB THD typical, not possible to sync from adapter to adapter.
Only one device per TEDS line is supported. Can be set to internal (adapter) or external (sensor).
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MSI - LVDT
2.2
2.2.1
Connectors
Input connector pinout
DSUB 9 connector
Illustration 1: 9 pin DSUB plug
Pin
1
2
3
4
5
6
7
8
9
Name
PS+
Out+
PSEnAGND
Reser.
PSEn+
OutPSTEDS
I/O
I, Power
O, Signal
I, Signal
I
I/O
I, Signal
O, Signal
I, Power
I/O, Signal
Description
Power Supply +
Adapter Output (Single ended) +
Power Supply Enable Analog Ground
Reserved / Not Connected
Power Supply Enable +
Adapter Output (Ground) Power Supply TEDS
Pin
1
2
3
4
5
6
7
8
Name
PS+
OutOut+
PSMGND
TEDS
AGND
Reser.
I/O
I, Power
O, Signal
O, Signal
I, Power
I
I/O, Signal
I
I/O
Description
Power Supply +
Adapter Output (Ground) Adapter Output (Single ended) +
Power Supply Mechanical Ground, chassis
TEDS
Analog Ground
Reserved / Not Connected
Pin
1
2
3
4
5
6
7
8
9
Name
Exc+
In+
SnsAGND
Reser.
Sns+
InExcReser.
I/O
O, Power
I, Signal
I, Signal
I
I/O
I, Signal
I, Signal
O, Power
I/O
Description
Sensor supply, excitation +
Sensor Output +
Sense Analog Ground
Reserved / Not Connected
Sense +
Sensor Output Sensor supply, excitation Reserved / Not Connected
Pin
1
2
3
4
5
6
7
8
Name
Exc+
InIn+
ExcMGND
Reser.
AGND
Reser.
I/O
O, Power
I, Signal
I, Signal
O, Power
I
I/O, Signal
I
I/O
Description
Sensor supply, excitation +
Sensor Output Sensor Output +
Sensor supply, excitation Mechanical Ground, chassis
Reserved / Not Connected
Analog Ground
Reserved / Not Connected
LEMO 2B.308 connector
Illustration 2: Lemo 8-pin plug
2.2.2
Output connector pinout
DSUB 9 connector
Illustration 3: 9 pin DSUB
receptable
LEMO 2B.308 connector
Illustration 4: Lemo 8-pin
receptable
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MSI - LVDT
2.3
Operation
Connect the LVDT Adapter to your SIRIUS or DEWE43 channel and connect to SENSOR input your sensor probe.
Set phase compensation
Select 4 or 10kHz sensor Excitation
Illustration 5: Adapter setting, frequency, phase
Depending on the sensor used select excitation frequency of the adapter as close as possible to required.
With phase compensation adjust the measured output to maximum output value.
2.3.3
Connections
LVDT – Differential
Half-Bridge LVDT
* 6-wire connection only shown. 4-wire also possible, connect Sns and Exc signals on adapter side of connector.
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MSI - LVDT
2.3.4
MSI adapters / TEDS sensor support
Since there is an inbuilt TEDS device in the adapter itself and if  MSI adapters/TEDS sensors under Hardware
setup is selected, adapter will be recognised and proper EXC. Voltage will be set automatically.
Please check if you are using the latest software where LVDT Adapter is supported.
Illustration 6: Setting – Hardware setup
Illustration 7: MSI adapters/TEDS sensors checkbox
Illustration 8: MSI-LVDT adapter is recognized and set automatically
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MSI - LVDT
2.3.4.1
Manual operation
If MSI adapters/TEDS sensors is left unchechked under Hardware setup then sensor supply and range has to be
set manualy.
Illustration 9: MSI adapters/TEDS sensors checkbox is left unchecked
Under Channel setup for channel N, set Excitation voltage from 10V to 15V maximum according to Table1.
Illustration 10: Excitation voltage setting
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MSI - LVDT
3
Documentation Version
Doc-Version
Date
[dd.mm.yyyy]
Notes
0.9
05.02.2014
Pre-release version
1.0
10.3.2014
New detailed descriptions for chapter 2.3.4
___________________
For support please contact support [at] dewesoft.com
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