MANUAL NO. 20405E1.2
Published in Dec.2004
Revised in Aug. 2007
LF Series
Ｌｉｎｅａｒ Variable Differential Transformer
INSTRUCTION MANUAL
LF SERIES
FOREWORD
For safe operation.....
Thank you for using our LS Series Linear Variable Differential Transformer (LVDT).
SHINKAWA Sensor Technology applies strict quality control and inspections to ensure the
high reliability of its products.
This instruction manual contains descriptive information, specifications, and operating setting,
and adjusting procedures.
Please study the contents of this manual and related manuals thoroughly before installing or
operating the equipment, and keep it handy for future reference.
"Safety Conventions"
Please thoroughly study the following section entitled "Safety conventions" before operating
the equipment.
The safety symbols explained in this section are placed outside the left margin next to the text
to which they apply.
This unit is designed for use by specialists or persons thoroughly familiar with the field.
Make sure that the end user receives the Instruction Manual delivered with this unit.
Before use.....
When the unit is received, inspect it for damage suffered in transport and check whether it is
the item you ordered. In the unlikely event that it was damaged in transport or does not
function according to specifications, please contact the SHINKAWA Electric Office or dealer
nearest you.
Store the unit under the ambient conditions given in the specification.
Avoid places where it is exposed to high humidity or corrosive gases.
Disuse.....
Please contact a nearly service station when disposal.
i
LF SERIES
SAFETY CONVENTIONS
Make it a rule to follow the instructions given in this manual.
This manual contains important information designed to prevent personal injury and property damage,
and ensure safe operation of the equipment.
Familiarize yourself with the signs and symbols explained below before proceeding to read the manual,
and observe the instructions given.
■ Explanation of signs
Symbols
Explanation
WARNING
Indicates a potentially hazardous situation which, if not avoided, could result
in death or serious injury.
CAUTION
Indicates a potentially hazardous situation which, if not a avoided, may result
in minor or moderate injury. It may also be used to permit for
property-damage-only accidents.
* “Serious injury” refers to such injuries as loss of eyesight, injuries, burns (due to heat or cold), electric
shock, fractures, and poisoning, that have permanent aftereffect and require hospitalization or
long-term outpatient treatment.
* “Moderate or minor injury” refers to such injuries as burns and electric shock that do not require
hospitalization or long-term outpatient treatment.
“Property-damage-only accidents” refers to consequential damage related to destruction of property
and damage to the equipment.
■ Explanation of symbols
Symbols
Explanation
Indicates a prohibited action.
Details are given in the text next to the symbol.
Indicates a mandatory action.
Details are given in the text next to the symbol.
ii
LF SERIES
CAUTION FOR SAFETY
In order to operate this product safely, observe the contents of the caution described in this instruction
manual.
Shinkawa will not bear the responsibility for any damage caused by their violations.
■ In order to operate the differential transformer safely!
CAUTION
Do not modify the differential transformer without permission.
MODIFICATION
PROHIBTION
MANDATORY
If modified, no product can be warranted.
Before conducting the megger test (insulation test) of signal transmission
cables, always disconnect the cables from the differential transformer and
combined converter. In addition, after the test, first discharge charged
electrons and then connect these cables to the respective devices.
If connected with electrons charged, an instrument connecting the LVDT may be damaged.
Be fully careful of handling the outer pipe and mounting blocks as they
easily slide.
Otherwise, fingers may get jammed in them or an injury may result during their handling.
In addition, instrument damage or injury may result due to their slipping out.
Always fix the transformer to the field fixture only using the outer pipe.
PROHIBITION
If fixed using the core & extension rod, deformation or breakage may result.
In addition, after being fixed, take the necessary measures for locking them.
Do not apply any movement of causing eccentricity to the differential
transformer when used.
PROHIBITION
If applied, the deformation of the outer pipe or the deformation or damage of the core &
extension rod may result.
Do not replace the core & extension rod.
PROHIBITION
Use the differential transformer body and its core & extension rod with the same
manufacturer’s serial numbers. If used in a different combination, the characteristics may
worsen.
Do not use the differential transformer as a footing.
PROHIBITION
This transformer may sometimes be installed at places where used as a footing at the power
generation plant site, etc. However never use it as a footing as this may cause its damage.
If there is a fear of being used as a footing, close it with a cover for its protection.
Installing environment
PROHIBITION
Use the transformer within the operating temperature range described in the specification.
If not, it may be damaged.
iii
LF SERIES
TABLE OF CONTENTS
1.
OVERVIEW
·························································································································
2.
1
STANDARDS
························································································································· 2-5
3.
REPLACEMENT OF PARTS
························································································································· 6-7
iv
1.
OVERVIEW
LF SERIES
1-1 OVERVIEW
The LF Series linear variable differential transformer (LVDT) is a compound wound differential
transformer designed by putting much emphasis on reliability and also so as to be most suitable for
valve opening
measurement.
1-2 OPERATING PRINCIPLE
The LF Series linear variable differential transformer (LVDT), as shown in Fig. 1, is a compound
wound differential transformer consisting of the primary and secondary coils and an iron core which
moves between them.
In Fig. 1, it is so designed that the iron core moves between the coils with the movement of an
extension rod. Thus, if the constant energizing current (8 V rms, 1 kHz and sine wave) is applied to
the primary coil, as shown in Fig. 2(a), the relationship of VCD < VEF is established between the
voltage VCD (between C and D) and the voltage VEF (between E and F) across the secondary coils.
Similarly in Fig. 2(b), the relationship of VCD = VEF and in Fig. 2(c), that of VCD > VEF are established.
As they change in proportion to the amount of iron core movement, as shown in Fig. 2(d), the voltage
in proportion to the amount of iron core movement can be output through a detection circuit by finding
the difference between VCD and VEF
8Vrms 1kHz
A
B Extnsion rod
Primary coil
Iron core
Secondary coils
C
D
F
E
Detection circuit(needs to be
prepared by the user.)
|VEF|
Output
Fig1. Diagram of showing construction
VCD<VEF
+V
|VCD|
VCD=VEF
0%
VCD>VEF
0V
Null point
100%
|VCD|-|VEF|
VCD
VEF
(a) 0%
VCD
VEF
VCD
(b) 50%(Null)point
VEF
(c) 100%
Fig 2. Diagrams of showing operating principle
-1-
-V
(d) Output characteristics
2.
STANDARDS
LF SERIES
2-1 SPECIFICATION
Model Code
LF100-1
Model Code
Stroke
L2(Outer pipe)
L3(NULL)
Sensitivity
Sensitivity error
100-2
250-1
100mm
-
250-2
250mm
300-1
400-1
300mm
400mm
488mm
902mm
488mm
539mm
565mm
610mm
593mm
1006mm
686mm
737mm
787mm
Shape of outer pipe
A
Without collar
883mm
13.0mV DC/Vrms/mm 5.20mV DC/Vrms/mm 4.33mV DC/Vrms/mm
3.25mV DC/Vrms/mm
±5%
LF100-1
Model Code
Stroke
L2(Outer pipe)
L3(NULL)
Sensitivity
Sensitivity error
AU
100-2
250-1
100mm
-
250-2
250mm
BU
300-1
400-1
300mm
400mm
503mm
917mm
503mm
554mm
580mm
625mm
608mm
1021mm
701mm
752mm
802mm
Shape of outer pipe
B
With collar
898mm
13.0mV DC/Vrms/mm 5.20mV DC/Vrms/mm 4.33mV DC/Vrms/mm
3.25mV DC/Vrms/mm
±5%
L2,L3 : Refer to Outline Drawing
SPECIFICATIONS
Stroke
100, 250, 300, 400mm
Excitation
8Vrms, 1kHz, sinusoidal wave
Operating temperature
-20 to +150°C
Linearity
Within ±1.0% of F.S.
Input impedance
More than 300Ω, 1kHz (at Null point)
Output impedance
Less than 250Ω (one side), 1kHz (at Null point)
Temperature drift
Dielectric strength
Within ±0.02% of F.S./°C
More than 100MΩ at 500VDC (between each lead wire and body, between primary coil and secondary
coil)
3mA or less at 1500VAC 60Hz for one minute (between each lead wire and body)
Shock vibration
98m/s (10g REF.) at 150Hz
Lead wire
0.2mm
Connected equipment
VM-21D or refer to following diagram.(prepared by customer)
Insulation resistance
2
2
: Prepared by customer
Excitation
A
Primary coil
B
LVDT
Output
F
C
Secondary coil
Lead color
A: Brown
B: Yellow
C: Red
D: Blue
E: Green
F: Black
D
E
Detection circuit
CONNECTION DIAGRAM
-2-
30307E1.4
2.
STANDARDS
LF SERIES
2-2 OUTLINE DRAWING
2-2-1
LF-□□□-□AU
Model code
100-1
Stroke
100-2
250-1
100mm
250-2
250mm
300-1
400-1
300mm
400mm
L1
20
20
20
20
20
20
L2
488
902
488
539
565
610
L3
593
1006
686
737
787
883
Dimensions : mm
7
6
5
4
3
2
1
No.
Lead wire
Mounting block 2
Body
Mounting block 1
Outer pipe
Jam nut
Core & Extension rod
NAME
-3-
2.
STANDARDS
2-2-2
LF-□□□-□BU
Model code
100-1
Stroke
-
LF SERIES
100-2
250-1
100mm
250-2
250mm
300-1
400-1
300mm
400mm
L1
20
20
20
20
20
20
L2
503
917
503
554
580
625
L3
608
1021
701
752
802
898
Dimensions : mm
7
6
5
4
3
2
1
No.
Lead wire
Mounting block 2
Body
Mounting block 1
Outer pipe
Jam nut
Core & Extension rod
NAME
-4-
2.
STANDARDS
LF SERIES
2-3 NAME OF EACH SECTION AND DESCRIPTION
PROHIBITION
1 Core & extension rod (hereafter called the “rod”)
Output voltage changes as the rod moves between the coils together with the movement of the
outer pipe ( 3 ).
Note:
The LVDT is fixed to the machine only using the outer pipe ( 3 ). Therefore never fix them using
the rod end thread (1/4-28UNF).
Machine side
1/4-28UNF
Outer pipe
Rod
Jam nut
2 Jam nut
Used to fix the rod to the outer pipe.
Note:
Do not loosen this jam nut. If so, the position of the rod ( 1 ) changes.
PROHIBITION
3 Outer pipe
The LVDT is fixed to the machine using the outer pipe.
As the rod ( 1 ) and the jam nut ( 2 ) are fixed to the outer pipe, the rod moves with the movement
of the outer pipe fixed to the machine.
Machine side
4 Mounting block 1
This block is fixed to the machine. In addition, it is not fixed to the outer pipe ( 3 ).
5 Body
There are coils inside the body which is fixed to the mounting block 2( 6 ).
6 Mounting block 2
This block is fixed to the machine.
7 Lead wires
Six lead wires with an area of 0.2 mm2 each are extended. They are covered with a protective
tube.
-5-
3.
REPLACEMENT OF PARTS
LF SERIES
REPLACEMENT OF PARTS
Each bearing used for the LVDT differs depending on the operating condition. However, it is
recommended that it be replaced with a new one after checking its rotating condition during
periodic inspection from the standpoint of preventive maintenance.
Note:
Conduct its replacement at places where solids do not fall onto it, nor tread foot passengers
on it.
For this replacement work, hot air (at a temperature of about 200°C) is required.
1 Separate the fixed block of the outer pipe from the machine.
Machine side
2 Remove all of the bolts fixing the mounting block 1.
3 Pull the outer pipe out of the mounting block 1 and body.
Rod
Mounting block 1
Outer pipe
Body
Note:
At this time, the pipe gets out of place
together with the outer pipe. After that,
do not bend nor scratch the pipe.
4 Pull the mounting block 1 out of the body and then remove all of the bolts fixing the mounting block 2.
Mounting
block 1
Mounting
block 2
Body
Wipe away dust attached to the body
and mounting blocks with waste
5 Remove each bearing from the respective parts.
Bearing 1
Bearing 3
Bearing 2
Rod
As the bearing 3 is an elastic tube, cut it away
with a cutter knife.
Through hole
Mounting block 1
Outer pipe
Remove the bearing 2 while pushing it in the
inward direction with a rod inserted through
the through hole.
At this time, do not bend nor scratch the pipe.
Body
-6-
3.
REPLACEMENT OF PARTS
LF SERIES
6 Replace all of these bearings 1 to 3 with new ones, respectively. (They are all made of Fluoro
resin.)
For each of the bearings 1 to 2, push it into the respective groove.
For the bearing 3, first pass the elastic tube through the body until aligned with the groove and
then contract it using the hot air. At this time, be fully careful that the elastic tube does not
protrude from the groove nor is wrinkled.
It is not necessary to apply
lubricant to each bearing.
Hot air (At about 200°C and for 15 to 20 sec)
7 Pass the mounting block 1 through the outer pipe.
Counterbored hole
At this time, be careful of the
direction of the counterbored
hole in the mounting block 1.
8 Pass the outer pipe through the body.
Outer pipe
Rod
Bearing 2
Bearing 3
Body
Rod
9 Fix each mounting block to the specified position.
10 Fix the outer pipe to the machine.
Machine side
11 Finished
-7-
Notes:
When inserting the rod into the body,
do not bend nor scratch it.
Do not forcibly insert the bearings 2 to
3.
Hiroshima Factory
4-22 Yoshikawa-kogyodanchi, Higashi-hiroshima 739-0153, Japan
Tel. 082-429-1118 Fax. 082-429-0804
[Field support & Repair Dept] E-mail : service@sst.shinkawa.co.jp