Sensor operating in forestry logging machine

Modern forestry logging machines are complex and sophisticated pieces of equipment able to fell and manoeuvre trees and trunks efficiently. To help control the hydraulic controls on the machines, sensors are fitted inside the hydraulic cylinders. The sensors provide feedback on the position of the rams to the main control system. The hydraulic cylinders are a compact design and have very little room to house the sensor and any associated electronics.

In this application it was necessary to design the sensor with a small space envelope in the cylinder and to use an external electronic interface. The Positek P106 inductive position sensor was chosen for this application because of its small size and the compact electronic interface. Usually the P106 sensor interface is mounted onto the body of the hydraulic ram. However, in this particular application the main system control electronics was mounted close to the cylinder. This meant that the Positek interface could be installed directly into the main module.The Positek interface is only 32mm diameter and is available as a double-sided surface mount PCB assembly. With integral pins and a specially moulded support ring it can be mounted directly onto the main control circuit. This assembly is very easy to assembly and eliminates the need for separate electronics enclosures and the associated wiring and connectors.

In the logging industry much of the work is carried out in the winter when temperatures can vary from -40° up to 40°C during the working day. This is a harsh temperature cycling routine and introduces special needs for the protection of electronics against condensation forming during the thermal cycling.

The P106 sensor incorporates technology developed by Positek and used in its other displacement sensor products. This PIPS® technology is based on inductive coils and uses a unique custom integrated circuit to produce an accurate analogue output signal.