361/362 sensors

361 and 362 clip-on sensors

There are two simple-to-use transportable sensors in the 300 series of modular digital readouts from BW Electronics: the 361 and the 362 clip-on sensors. Both are robustly constructed in a die-cast aluminium box with mounting tube. The sensors have different measuring ranges.

The 361 and 362 clip-on sensors (right) compared with the standalone MPS2 single-axis readout
Some of the sensors available from BW Electronics: ¬≠the Micro Position Sensor 2 (MPS2), the 361 clip-on sensor (top right), and the 362 clip-on sensor (bottom). The MPS2 and 361 sensors each have a maximum measuring range of 20 inches or 500 mm, making them ideal for the smaller machine tool. The 362’s maximum measuring range is 48 inches or 1200 mm. Also shown are the standard plastic pipe clips used for mounting the clip-on sensors.

Both sensors use standard pipe clips (8 mm or 12 mm) on the machine, which clip onto the tube on the sensor. This enables the sensors to be moved between machines. The measuring wire entry is sealed with a PTFE bush.

The maximum measuring range of the 361 clip-on sensor is 500 mm or 20 inches. The sensor size is 52 x 38 x 32 mm plus a 8 mm diameter mounting tube.

The measuring range for the 362 is extended to a maximum of 1200 mm or 48 inches. The sensor size is 110 x 60 x 30 mm, with a mounting tube 65 mm long and 12.7 mm diameter.

How the sensors work

All the sensors from BW Electronics use a similar measuring method, based on an extending stranded stainless-steel wire, much like a tape measure.

The measuring wire is wound around a small drum inside the sensor, which also has a restoring spring. As the wire is pulled out or returned under the spring tension, the wire winds off or on the drum.

The drum has a thread cut on its outside diameter to ensure the wire winds cleanly on and off, with no overlapped turns.

Attached to the drum is a rotary optical encoder that measures the rotation; signals from the encoder are counted to give the distance moved.

This method of measuring makes it particularly easy to fit sensors on smaller machine tools.

  • The measuring wire has minimal cross-sectional area, so it can be squeezed into very restricted spaces.
  • Being flexible, the wire can be taken around pulleys to change direction, avoid obstacles etc.
  • The measuring wire can be taken around curved objects such as a rotary table to measure angles.

Because the sensors have been expressly designed to be moved from machine to machine, this drastically reduces the cost for equipping a whole workshop with DROs. For example, a small workshop needs only two MPS3s, or one 300 series display (such as the 332 or 334) and two clip-on sensors, to equip all the machines.

Experience has shown, however, that moving the 362 sensor is not a good idea. There is so much wire in it that it inevitably seems to get caught and damaged. If you can get away with using a 361, then that is to be preferred.

Digital Position Readouts for smaller machine tools