What the system must achieve
provide trendable displacement data to an RTU or monitoring platform
Technical selection, cross-reference and global export supportSend a model or application →
Draw-wire sensor application
Draw-wire Sensors for Bridge and Joint Displacement
Monitor expansion-joint, bearing or structural movement over medium and long travel.
01 · THE MACHINE
relative structural movement
A draw-wire displacement sensor measures relative structural movement by extending a spring-retracted stainless-steel cable from a fixed sensor body to the moving point. The correct configuration combines measuring range, 10- or 12-bit absolute resolution (or 1,000/2,000 PPR incremental output), controller interface and IP54, IP68 or project-confirmed Ex protection.
In plain termsFirst identify the movement the controller needs to know. Only then choose the encoder.
02 · WHAT TO MEASURE
Fix the body to a stable reference and attach the cable only to the measured point.
define a stable datum and review weather, corrosion, traffic vibration, cable protection and maintenance access
- ✓Stable datum
- ✓Straight cable path
- ✓Overtravel allowance
VIEW PRODUCT PAGE →03 · RECOMMENDED PRODUCT
IP68 Waterproof Draw-wire Sensor
Select the measuring range before choosing the output and enclosure.
The selected travel determines the mechanical family, housing dimensions, winding wheel and pull force. The controller interface and environmental protection are then matched to the installation.
✓ Measurement: relative structural movement✓ 0.5–10 m plus shared 12–15 m 2D option✓ RS485, CANopen, SSI, BiSS-C, analog and pulse options✓ IP54, IP68 and project-confirmed Ex versions
View product parameters →04 · HOW IT WORKS
From machine movement to a control decision.
The draw-wire sensor converts a moving point into a continuous linear position value.
WHAT THE SENSOR DOES
A spring-retracted measuring cable follows the moving mechanism. The internal encoder converts cable-drum rotation into an absolute digital, analog or incremental signal for the machine controller.
- 01MOVEMENTLinear movement
- 02SENSINGRange-matched draw-wire
- 03SIGNALPosition signal
- 04CONTROLPLC / RTU / controller
How we select the sensor
Measure the full working travel and add appropriate setup and overtravel margin. Choose 10/12-bit absolute feedback or 1,000/2,000 PPR incremental feedback. Match RS485, CANopen, SSI, BiSS-C, analog or pulse output to the controller. Approve the range-specific housing and drawing; define a stable datum and review weather, corrosion, traffic vibration, cable protection and maintenance access.
05 · EXPECTED RESULT
What improves after the correct feedback is installed.
SELECTION TABLE
Application requirement and selection response
Use this table as an initial engineering checklist. Final model configuration must be confirmed against the controller, mechanical drawing and operating environment.
Engineering questionWhat to confirm
Movementrelative structural movement
System goalprovide trendable displacement data to an RTU or monitoring platform
Sensor selectionTravel plus overtravel margin, resolution, output and protection
Installationdefine a stable datum and review weather, corrosion, traffic vibration, cable protection and maintenance access
ENGINEERING PROCESS
How to select the right configuration
- 01
Measure the full working travel and add appropriate setup and overtravel margin.
- 02
Choose 10/12-bit absolute feedback or 1,000/2,000 PPR incremental feedback.
- 03
Match RS485, CANopen, SSI, BiSS-C, analog or pulse output to the controller.
- 04
Approve the range-specific housing and drawing; define a stable datum and review weather, corrosion, traffic vibration, cable protection and maintenance access.
RELEVANT PRODUCTS
Technical product pages
IP68 Waterproof Draw-wire Sensor
Protected linear-position measurement for outdoor, washdown and water-infrastructure applications.
View parameters and drawings →
RS485 Modbus Draw-wire Displacement Sensor
Absolute linear position and speed feedback with power-off memory for short, medium and long travel.
View parameters and drawings →
Analog Draw-wire Displacement Sensor
Direct analog linear-position feedback for standard PLC current and voltage inputs.
View parameters and drawings →COMMON QUESTIONS
Frequently asked questions
Can the measuring cable carry the machine load?
No. It is a measurement element only and must never be used as a load-bearing or safety-support cable.
How is the housing selected?
The selected travel determines the BRT27 or BRT38 mechanical family, housing dimensions, winding-wheel diameter and nominal pull force.
Does IP68 cover every outdoor installation?
No. Confirm the complete assembly, cable exit, corrosion exposure, mounting orientation and the supplier's stated water test condition.
RELATED GUIDANCE
Continue your selection
EDITORIAL SCOPE
How this guidance is prepared
FOSAI consolidates available supplier technical material into a buyer-oriented selection guide. Parameters, certifications and compatibility are not generalized across every model; the final suffix, controlled drawing and project conditions must be confirmed before ordering.
MODEL SELECTION SUPPORT
Send the model.
We’ll check the complete fit.
Include the existing model, controller interface, supply, measurement range, shaft or mounting drawing, environment and quantity.
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