News

Autonnic's new sensors for engine lever controls - November 10, 2009

A major requirement of the marine world is that conducting, corrosive seawater must not encounter electronic circuits. Yet controls, switches and buttons must be placed where a wet mariner can reach and touch them.

Having developed and patented some unusual aspects of fluxgates, Autonnic has applied the latest version of its 3-axis fluxgate technology to the solution of this interface problem. Autonnic’s solution is magnetic and therefore non-contact which solves the problem of how to keep the sea out of the electronics behind knobs, levers and buttons.

First of the series to launch is the A3300 set of OEM modules to provide the basis of non-contact engine lever controls for either one or two engines.

Originally based on cables, lever controls are the electrical means to communicate between the bridge and engine room. Fundamental to the operation is a method to convert a hand movement into an electrical signal. While a potentiometer is often used it has a number of disadvantages and Autonnic’s challenge has been to solve these while remaining cost-effective.

Firstly, potentiometers are not non-contact. The electrical part is mechanically connected and a rotary seal is therefore needed to keep the water out.

Secondly, potentiometers use sliding parts which wear and give rise to electrical noise which could lead to unreliable operation.

And thirdly, the potentiometer is itself a mechanical turning part and its own movement has to be rigidly accommodated within the final lever product design.

Autonnic’s solution is, naturally, based in its inherently low-cost magnetic technology. At its simplest we apply a magnet on a lever externally and a sealed internal fluxgate will indicate to what angle the lever has been turned.

But for adjacent controls, such as a twin engine lever control, something else has to be put in place; Autonnic’s Switched Magnet Technology. (SMT)

By using asymmetric passive cores on the lever shafts a common fluxgate can be shared between the two keeping all the advantages. Because SMT is a Vector Magnetic method it means that the background field is always being removed from the reading leaving it unaffected by stray magnetic fields.

And finally for the highest precision applications - higher even than lever controls - Autonnic can replace the passive cores with excited symmetric cores so that the movement of one shaft does not distort the field due to the other in even the slightest way so that cross-talk is completely eliminated.