Rotary Position Sensors (OEM)

For LINTRAN and IncOder product ranges the air gap is specified in the relevant data sheet.

More generally, it’s easiest to answer this question using a couple of examples:

Firstly, if we consider a linear Antenna 10mm wide and 100mm long in the measurement axis, then the maximum working distance of the Target from the Antenna will be about half the Antenna width i.e. 5mm. We normally recommend a stand off distance of <1/4 Antenna width – so about 2-3mm.

In a rotary example, with an Antenna whose O.D. is 50mm and an I.D. of 20mm then the equivalent Antenna width is 15mm (the thickness off the annulus). Again the maximum working distance of the Target from the Antenna will be about half the effective Antenna width i.e. 7,5mm. We would normally recommend a stand off distance of <1/4 Antenna width – so about 3-4mm.

We have built lots of linear sensors with a maximum full scale defelection of 0,1mm and a resolution of <1micron.

For rotary devices, we have buit sensors with targets and diameters of 12.7mm.

The longest we can build from circuit board is 2,7m but it is possible to build much larger sensors using wire or tape constructions.

Firstly, a number of parameters related to ˜accuracy’ are important for sensors. These are usually linearity, resolution and repeatability. The exact parameters for any series of Zettlex sensors primarily depend on the sensor geometry and, in particular, any variability of the position of the target in axes other than the measurement axis. Other factors effect performance to a much lesser degree. As a general rule:

• Linearity is typically <<1% of full scale and can be <0.0001% of full scale.
• Resolution is typically <24 bits but most commonly 10, 12, 14, 16 or 18 bit
• Repeatability is typically +/- 1 least significant bit of the quoted resolution.

First of all talk to us – we might have an existing design that will suit. In case we don’t have a similar existing design, we can modify an existing one or develop a new one to suit your needs.

The first stage in developing an application specific Zettlex system is to discuss the specific technical requirements with us.

The most important aspects are sensor geometry, accuracy, speed & electronic output. From this a Requirements Specification can be drafted as a first step in the development process – we can help you do this. Zettlex follows a tried and tested development process leading to full-scale production.

Yes. It is possible in some instances of relatively simple machine control to integrate machinery control software in to the microprocessor containing the Zettlex sensor software.

Power supply, frequency generation etc. can also be shared between host and sensor system.

Generally, Zettlex position sensors are not susceptible to far field emissions up to field strengths of 150 V/m. This covers the vast majority of possible applications including most medical and aerospace applications.

However, in some defence applications higher field strengths can be accommodated with the use of special targets or simple, low-cost shielding and earth planes.

Zettlex applications comply with EN 68000 and CISPR 25 level 1 or 2.

Yes. The standard Zettlex sensor software can be parameterized to control multiple sensors of differing geometries.

In principle, a metal shield can be inserted between a sensor’s Target and an Antenna.

The skin depth through which the excitation signals can permeate limits the thickness of the metal shield. The lower the excitation frequency, the greater the thickness of permissible metal.

The maximum thickness of metal depends on the actual metal. If a metal shield is to be used then non-magnetic stainless steel is most preferred with aluminium, steel, copper or brass least preferred. Practically, metal thicknesses of <1.6mm are necessary.

Cost depends on a number of factors such as measurement specification, size, environmental conditions and size. Please contact us via the Contact Us page with details of your applications and we will provide a budgetary quote in a few days. Alternatively, you can get a rough idea of (low volume) product costs from the Store part of this web-site.

Practically, the materials, from which the sensor’s main components are produced, limit the operating and storage temperatures.

Importantly, the sensor’s fundamental operating principles are not affected by temperature. That means Zettlex sensors can operate in relatively low or high temperatures.

Most frequently, the effective temperature range is limited by the electronic components at –40 to 85 or 125 Celsius (i.e. industrial or automotive ranges).

However, it should be noted that the sensor’s electronics can be displaced away from the Antenna. This enables the sensors to be designed such that only the Antenna and Target are placed in harsh temperature environments whilst the Electronics are placed in a more benign environment away from, or insulated from, the harsh conditions.

Ceramic substrates for the Antennae and Target substrates can be used to increase temperature limits.

We have built sensors that can withstand constant operation at +230 Celsius and we are developing sensors for +450 Celsius.

We have built sensors to operate in -55 and -60Celsius.

The maximum distance between Electronics and Antenna is determined by two main factors – the coupling factor between Target & Antenna and the application’s electromagnetic environment or EMC requirements.

The greater the signal amplitudes in the Antenna’s Receive circuits and the more relaxed the EMC environment, the greater the permissible displacement between Electronics and Antenna.

The use of EMC shielded cable between Antenna and Electronics generally increases the maximum permissible distance. In consumer electronics applications a distance of 2m is achievable without the use of shielded cable between Electronics and Antenna.

Zettlex can advise on maximum distances given a particular sensor geometry, size and relevant EMC data.

The IncOder and LINTRAN product ranges are unaffected by nearby metal objects.

Nearby metal objects need only be considered for OEM or unpackaged sensors – in other words, those that will be located in a host mechanical structure. You will see on some of our data sheets for OEM or unpackaged sensors a metal ‘keep out’ zone.

Metal objects – or more specifically conductive objects – will only influence Zettlex sensors if they are in close proximity to the sensor’s windings. These windings are on the main faces of the sensor’s antenna (stator) or target (rotor). The magnetic properties of such materials has no influence – the dominant effect relates to their conductivity.

Conductive materials may influence the sensor’s field when they are in close proximity to the sensor’s windings because they may provide a flux path for the sensor’s field. This may affect the sensor’s measurement performance.

To most intents and purposes when we talk of metal objects we are also talking about conductive objects. In other words, objects made from aluminium, steel, stainless steel, brass, copper, cast iron etc. The conductivity of materials such as polymer, glass, water, potting compound or ceramic has no effect.

Metal objects around the periphery or external edges of a Zettlex sensor’s windings have little or no effect. Accordingly, metal shafts through the centre of a rotary sensor or a metal housing around the periphery of a rotary, linear or curvi-linear sensor have little or no influence.

The main point for consideration is metal objects close behind the sensor’s antenna (stator) or rotor (target).

For a rotary sensor whose windings have an inner radius r and outer radius R, metal objects need only be considered if they are closer than (R-r)/2 to the rear faces of the stator or rotor. These are typically the dimensions of the metal keep out zone shown on some Zettlex data sheets. Metal objects can encroach within this area either if they are lower conductivity (e.g. stainless steel); have a small cross-sectional area relative to the area of the windings (e.g. a small diameter dowel or pin) or are of constant planar aspect (e.g. a planar sheet of steel or copper). In such cases it is usually permissible for the metal objects to approach within (R-r)/4 of the rear faces of the stator or rotor windings without affecting measurement performance.

For a linear or curvi-linear sensor whose windings have length L (along the measurement axis) and width t (across the measurement axis), metal objects need only be considered if they are closer than t/2 to the rear faces of the antenna or target. These are typically the dimensions of the metal keep out zone shown on some of our data sheets. Metal objects can encroach within this area either if they are lower conductivity (e.g. stainless steel); have a small cross-sectional area relative to the area of the windings (e.g. a small diameter dowel or pin) or are of constant planar aspect (e.g. a planar sheet of copper or steel). In such cases it is usually permissible for the objects to approach within t/4 of the rear faces of the antenna or target windings.

Metal objects outside the dimensions stated above have no influence on sensor performance.

In some instances it is not feasible for metal objects to sit outside such exclusion zones. In such instances, please contact Zettlex – we may be able to modify a sensor design so that it will cope with very close metal objects. This has successfully been accomplished on numerous occasions previously when space has been of paramount importance.

A typical power requirement is 5V/10mA or 24V/3mA – but this is at 100% duty cycle. Power usage can be reduced (e.g. for extending battery life) by the use of a sleep cycle – thus reducing the effective duty cycle.

A sleep cycle can be implemented by, for example, using an algorithm which measures displacement once every 10 seconds (equivalent to a 0,1% duty cycle) and reverting to 100% duty cycle should the displacement have changed. In turn, the sensors can then revert to sleep mode if the displacement does not change again for a period of say, 10 seconds.

In theory, a Target can carry an infinite number of identities. Practically, a Target is limited to about 8 frequencies and hence 8 identities.

However, an object can carry multiple Targets – hence multiplying the possible number of identities.

Furthermore, the relative distance and orientation of the Targets can be sensed by an Antenna, thus multiplying the number of identities still further.