Today's encoder users expect flexibility, reliability, easy installation, immediate availability, and above all, useful and innovative new features at attractive prices. This fantasy has become reality in a new encoder generation that achieves an unprecedented synthesis of custom-designed OPTO-ASICs with a modular mechanical concept.

Solution to a Paradox

Whenever exact information about speed or position is required, machine builders and system integrators rely on incremental and absolute encoder feedback. Until now, manufacturing of incremental encoders was dominated by the creation of customer-specific line counts. This required that unique disks be created and kept in stock by the manufacturers. However, due to varying application requirements, a variety of line counts as well as mechanical and electrical interfaces were required.

Consequently, encoder production was typically made-to-order, resulting in increased lead times and cost. Often designs were not even realized, because unique features made them too expensive.

The solution lies in a new generation of incremental and absolute encoders that use modules with identical Custom-designed Hybrid OPTO-ASICs. These Core Modules, in combination with a set of mechanical components and driver PCBs, allow manufacturing and shipping of any resolution and electrical or mechanical configuration within 48 hours.

Now users can pick their custom model from over 10 million versions. Any line count from 1 to 8,192 for incremental and any step from 2 to 32,768 for absolute encoders is standard. Keeping spare encoders on the shelf becomes unnecessary, which reduces inventory cost and simplifies logistics for users.

The Heart of It All

The new CoreTech® concept combines the proprietary Stegmann OPTO-ASIC with a unique barcode carrying code disk. Unlike conventional code disks, where parallel tracks with repetitive patterns of opaque and transparent fields form a position code, the very small CoreTech® disk condenses absolute position information into a single non-repeating circular barcode pattern. A second track with 1024 sin/cos cycles enhances resolution and accuracy. As a result, encoder type -- incremental or absolute -- and resolution can be selected via firmware for each CoreTech® module.

The new pickup system is very different from conventional designs. A sophisticated sensor array of selectively accessible elements represents the sensitive area of the OPTO-ASIC. Instead of a parallel position readout along the radius in a specific disk location, the sensor array reads complete serial data strings from the barcode information. Simultaneously, other sensor elements read the very precise sin/cos information, which is transformed into a high-resolution ARCTAN value within the ASIC. After synchronization of both inputs, position information with high resolution and accuracy is available. Because sensor array and barcode track are adjusted to each other in size, position data is available at a single glance, and, unlike pseudo-random code devices, no angular movement is required. The highly integrated ASIC provides all data in real time.

High signal quality and noise immunity is guaranteed by differential sensing technology. Only the difference of a sensor pair's output signals is amplified. While one sensor reads the transparent or opaque areas of the original code, the other simultaneously reads the complementary pattern. Due to the physical closeness of the sensor pair, common mode noise from temperature, electronics, mechanical stress, and stray light affects both sensors the same way. Because the noise effects possess the same polarity and electrical phase, they can be eliminated by amplifying only the difference of both signals.

An integrated LED current controller adjusts for aging and temperature drift, while a minimum of electronic components enhances reliability. All major encoder features are embedded into the ASIC and integrated monitoring functions enhance system safety.

This new technology for the first time allows the implementation of an electronic zero pulse for incremental encoders. Typically the zero pulse of 90º or 180º electrical width is transmitted once per revolution. It is a reference relative to a defined mechanical position and is mainly used during commissioning. It also serves to find the reference position during a homing procedure, e.g. after power loss.

Up to now alignment of the zero pulse was costly and tedious, because the encoder had to be detached and manually rotated to achieve proper alignment. With CoreTech® the zero pulse is assigned by software -- via set line or push button -- to the current encoder position. No mechanical adjustment is necessary, which makes it accurate and timesaving for service personnel.

The basic element of all CoreTech® encoders is always the Core Module. This allows manufacturing in high quantities, resulting in a high and reproducible quality standard and competitive pricing. The only other components required to ship any encoder version are standard shafts, sleeves, housings, and interface PCBs.