HEIDENHAIN PWM 20 - Manual (Page 98)

November 2014 Software description 99
At the beginning of the diagnostics dialog you must select:
Open Loop: The encoder is directly connected to the test unit (open loop).
Closed Loop : The PWM 20 is looped into the absolute measuring circuit via the IN/OUT socket
(observe the chapter "Feed-through mode"), or a Service Adapter (SA 1x0) is used for floating
connection.
Two diagnostic modes are available:
Open Loop
The control loop of the machine is open, and the encoder is directly connected to the test unit
(without subsequent electronics). For the inspection the encoder must be traversed by hand.