The advantages of a draft wire encoder
Draft wire encoders are somewhat less known as linear measurement systems. Therefore, they are not often considered as a solution in a new design for an industrial application. But there are some good reasons why engineers should appreciate their functional properties. After all, they can be an excellent solution for required measurements.
Read more on the following topics:
- What is a draft wire encoder?
- Why a draw-wire decoder?
- Which drawbar encoders are available?
- When is a traction wire encoder used?
What is a pull-wire encoder?
A tensile encoder is a measurement system consisting of two components integrated into one system.
A rotary encoder
This can be optical or magnetic, with incremental, absolute or analogue outputs. (A potentiometer can also be incorporated)
A stainless steel measuring wire
The (pull) wire is wound in a coil unit with spring. The pull-up wire is then pulled out and rewound during operation. The stainless steel wire is attached to a moving shaft that is measured. The encoder is coupled to the winder unit. So when the wire moves back and forth, the encoder is rotated.
In this way, the linear movement of the wire through the drum is converted into a rotational movement and then by the encoder into a position. The measuring wires are available in different lengths. In addition, the flexible wire can make a curved path through guided rollers.
The measuring wires offered by Lika Electronics have a range of 2 to 50 metres.
Why a pull-wire encoder?
Let us assume that the roll-up unit is the fixed part in the measurement system. It is also immediately the most vulnerable part. The pull-up wire is attached to the movable part whose position is to be measured. This is the most robust part of the pull-up wire encoder.
The retractor unit can therefore be mounted away from the object to be measured. Bear in mind that it can therefore be at a safe distance from difficult environments with harsh environmental conditions (dirt, high temperature, humidity, etc.).
In addition, the head of the pull-up wire has a compact size, so little space is required to still be able to attach a measurement point. Indeed, the winder unit is a little further away where there is more space.
Lika has several encoders that can be mounted on the same roll-up unit (depending on the type). This allows us to be very flexible in terms of applications and environments.
Which draw wire encoders are available?
With programmable incremental encoder
Resolution down to 0.01 mm / 10 µm (16,384 PPR), universal output circuit HTL/TTL, fully configurable according to needs via free software tool.
With SSI and analogue absolute encoder
Resolution up to 0.012 mm / 12 µm; analogue version with TEACH-IN keys and overrun safety function, current and voltage options.
With Ethernet and fieldbus absolute encoder
Profinet, EtherNet/IP, EtherCAT, POWERLINK, MODBUS TCP, Profibus, CANopen, DeviceNet, MODBUS RTU. This makes Ethernet technology available in the most uncomfortable conditions (the smallest rooms, harsh industrial environments). Resolution up to 0.024 mm / 24 µm, full set of configuration and diagnostic parameters: position and speed readout, full scaling, preset, code sequence, extended diagnostics, Ethernet and bus network settings.
Resistance values from 1 to 20 kOhm, current and voltage output
With ATEX incremental and absolute encoder
Category 2 ATEX encoder for use in zones 1, 2, 21, 22 and Category 3 ATEX encoder for use in zones 2, 22 with ultra-rugged housing, oversized frame walls and IP65 sealing.
Special encoder versions
Designed for individual applications such as towing encoders for the shipbuilding industry, marine installations and offshore facilities with stainless steel housings and special surface treatments and seals for saltwater and corrosion protection.
When a draft wire encoder?
An encoder driven by a draw wire can replace a standard encoder in many applications. For example, it can be a good solution when working space is limited or the application is in an extreme environment.
This is because the encoder housing can be mounted in a safe place, easily accessible and adequately protected. This while the measuring wire requires minimum space and can be exposed to harsher conditions.
Applications and uses
Typical applications are mobile equipment and construction machinery (outriggers, stabilisers, arches), telescopic cranes, excavators, forklifts, guided vehicles, agricultural and forestry machinery and equipment, scissor lifts, car lifts, loading platforms, warehouses, electro-medical equipment (scanners, operating and examination tables, hospital beds, dentist's chairs, etc.)