HEIDENHAIN PWM 20 - Manual (Page 22)

August 2014 Overview of cables and adapters 23
DANGER
Integrating a PWM 20 into the control loop has an influence on power supply and
grounding conditions (see instructions "Installation/Commissioning“ ID 729905-91).
The feed-through function must be handled with great care and caution!
No persons are allowed within the working range of the machine!
Ensure that vertical axes cannot fall down!
Do not disengage any connecting elements during the measurement!
Move the machine axis to the middle of the traverse range before you connect
the PWM 20!
When you have connected the PWM 20 into the control loop of the machine, check
whether the axis concerned can be traversed in a controlled manner.
One operator must be at the EMERGENCY STOP switch to make sure that the
machine can be switched off at any stage of this "setup phase"!
Possible axis behavior caused by grounding problems:
- Uncontrolled machine movement
- Machine switches off (EMERGENCY STOP)
- Machine axis drifts
- Machine axis accelerates with rapid traverse
Note
HEIDENHAIN recommends running the feed-through mode with floating supply with the
service adapters SA 100 / SA 110.
Note
The encoder output (OUT) of the PWM 20 must not be connected,
 if the PWM test setup was prepared for feed-through operation.
 if an absolute encoder on a machine axis is supposed to be inspected while the machine is
not switched on (e.g. reading out the encoder memory to determine the encoder model).
Therefore, the output cable to has to be disconnected from the control for this special test.
Reason: As long as the control is connected, the terminating resistors of the PWM 20
encoder output disturb the measuring function.