Mount Encoders

The telescope has 3 axes - azimuth, elevation, and rotator.

The elevation axis has 4 encoders (of which we are now using two). It has a pair of motor encoders (that we do not now use), a pair of tapes (one of which does not work), and an inductosyn. We use the working tape to supply feedback to the lm628 and the inductosyn to drive the outer servo loop.

First and foremost, the elevation encoder data in the tune display (and all the outward mount displays) is from the elevation inductosyn.

The tape supplies the feedback signal to the lm628, but has no apparent outside world display.

The Elevation inductosyn has 65536*512/360 = 93206.76 counts per degree.

The Elevation tape has 181969.5 counts per degree with 25x interpolation (about double the inductosyn).

The motor incremental (that we no longer use) has 274829.55 counts per degree (with 25x interpolation).

A single inductosyn cycle (512 per 360 degrees) is about 0.7 degrees, This value sometimes appears as a "jump" on the tune display when the encoder electronics malfunctions.