HEIDENHAIN PWM 20 - Manual (Page 19)

20 HEIDENHAIN PWM 20 Testing Package – Cable and Connection Technology
Grounding
conditions The PWM 20 features an internal wide-range switching power supply. The PE terminal
(protective earth), which is also connected with the PWM 20 housing, is therefore required.
If the PWM 20 is integrated in the position control loop of an NC-controlled machine, the
PWM 20 constitutes an additional grounding point, which changes the shielding concept.
To prevent this,
 the PWM 20 can be supplied via an isolating transformer,
 the PWM 20 can be supplied with 24 VDC.
To evaluate the PWM 20 measuring data, a PC is connected to the USB interface of the
PWM 20. The 0-V potential and the protective earth terminal are usually connected to each other
in the PC (also USB). If the PWM 20 is integrated in the position control loop of an NC-controlled
machine, the conditions on the 0 V connection change, too. To prevent this,
 you can use a battery-operated laptop computer,
 the laptop can be used with a power supply unit without protective earth terminal.
Feed-through
operation
(listening-in) with
PWM 20 in the
position control
loop of an
NC-controlled
machine tool For diagnostic purposes, the PWM 20 can be integrated into the control loop of an NC-controlled
machine via the encoder input and output (see "Encoder Output"). In this case, please not the
changed grounding conditions and the situation of the supply voltage (see "Encoder output").
Depending on the ATS software version and under compliance with the notes listed above,
the PWM 20 can be operated in a closed loop. However, using a signal adapter (e.g. SA 100,
SA 110, …) is always required, or recommended.
The following applies in addition:
1. Switch off the machine!
2. Then disengage the connecting elements!