Posted to News on 16th Sep 2020, 16:15
Machine safety without SIL: WDG series redundant encoders from Wachendorff
Wachendorff, the German measurement systems manufacturer, has recently launched redundant versions of its well proven WDGR and WDGE series of incremental and absolute encoders
The new encoders are now available from Variohm EuroSensor, Wachendorff´s exclusive UK distributor, and combine disparate optical and magnetic measurement principles that are independently correlated yet fully synchronised through separate processing electronics. Wachendorff says that it sees the new products as a cost effective alternative to expensive Performance Level d or SIL 3 based safety systems.
Two encoder versions are available: the WDGR combines incremental magnetic and incremental optical encoders whilst the WDGE combines absolute magnetic and incremental optical technologies. Both have a 58 mm diameter clamping flange mounting with a choice of shafts from 6 mm to 9.525 mm diameter. The resolution for the WDGR is up to 1024 ppr magnetic and up to 5000 ppr for the optical encoder. For the WDGE series the magnetic absolute encoder has a 16 bit single-turn and a 43 bit multi-turn resolution, whilst the incremental encoder resolution is up to 5000 ppr.
The 58 mm diameter WDG series is claimed to be especially durable with high interference immunity thanks to a magnetically shielded and chrome plated steel housing. A zinc plated connector cover houses a choice of PG cable glands or M12 x1 connectors for each encoder. The entire housing has an IP67 protection rating with IP65 for the shaft assembly where a stainless steel shaft is supported on a pair of precision ball bearings for up to 220 N radial and 120 N axial load ratings. With a maximum operating speed to 8000 rpm, the nominal bearing life is 1 x 10-9 revs. at full load with 1 x 10-11 revs. for 20% load.
The optical sensor technology used in both versions has a wide choice of industrial standard compatible power supply options which are completely separate for the two encoder types - further reinforcing the redundant design. Both encoder models have incremental encoders with output options that include TTL, HTL and 1 Vpp sin/cos. The magnetic encoder in the WDGR model has HTL and HTL-inv output whilst the WDGE´s magnetic encoder output is CANopen with a CiA 301 communication profile.
Following the principle that the different sensor platforms would react with differing sensitivities to disturbances and therefore would not fail simultaneously, these new dual redundant encoders are said to offer high reliability with appropriate control systems where, for example, speed detection or loss of position would be problematical. Specific details and application support for the new WDG redundant series encoders and Wachendorff´s entire range of sensor products is available from Variohm EuroSensor.
