HEIDENHAIN TNC 407 (243 020) Service Manual - Manual (Page 59)

SERVICE MANUAL TNC
Issue:
01.09.1995
Page 50
11.3.1 Electrical Check of Encoders
In
order go give a precise statement on the electrical function of an encoder, it must be measured with a phase
angle measuring unit an oscilloscope and an impedance tester. (see operating instructions Encoder
Diagnostic Kit)
If no phase angle measuring unit is available, the electrical state of the cable, the lamp and the photocells of
an encoder can be checked with an ohmmeter. The following resistances must be measured at the connector
of the encoder:
Encoder connector housing against machine housing (external shield)
Encoder connector housing against pin 9 (internal shield against external shield)
Encoder connector housing against pins 1 to 8 (external shield against signal lines)
Pin 9 against pins
1 to 8 (internal shield signal lines)
Pin 1 against pin 2 0”
Pin 2 against pin 1 0” (switch poles of ohmmeter)
Pin 5 against pin 6 90”
Pin 6 against pin 5 90” (switch poles of ohmmeter) The measured values should
Pin 7 against pin 8 ref. pulse be approximately equal.
Pin 8 against pin 7 ref. pulse * (switch poles of ohmmeter)
Pin 3 against pin 4 5 30
*If encoders with selectable reference marks are used, different resistance values are measured no
resistance), depending on the type of activation.
**The encoder check (pin 3 against pin 4) can only be carried out, if the encoder light unit is a lamp. With
encoders with an amplifier section, the light unit cannot be checked at all. With encoders with infrared diodes
a resistance in the conducting direction can be measured between pin 3 and pin 4
Basic Circuit Diagram with Sinusoidal Signals
Encoders with square-wave output signals can only be tested with a phase angle measuring unit