HEIDENHAIN TNC 306 Service Manual - Manual (Page 54)

SERVICE MANUAL TNC 306/360
Page 47
HEIDENHAIN Service
11.3.1 Electrical Check of Encoders
In order to give a precise statement on the electrical function of an encoder, it must be
measured with a phase angle measuring unit (PWM), 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:
Measure resistanfce of:
- Encoder connector housing against machine housing (external shield) should be < 1
Ω
- Encoder connector housing against PIN 9 (internal shield - external shield) R =
∞
- Encoder connector housing against PIN 1 to 8 (external shield - signal lines ) R =
∞
- Pin 9 against Pin 1 to 8 (internal shield- signal line) R =
∞
- Pin 1 against pin 2 0°
- Pin 2 against pin 1 0°
- Pin 5 against pin 6 90°
- Pin 6 against pin 5 90°
- Pin 7 against pin 8 RP1)
- Pin 8 against pin 7 RP1)
- Pin 3 against pin 42)
(switch poles of ohmmeter)
(switch poles of ohmmeter)
(switch poles of ohmmeter)
(approx. 5 - 30
Ω
)
The measured values should
be approximately equal.
1) If encoders with selectable reference marks are used, different resistance values are
measured (or no resistance), depending on the type of activation.
2) 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 Signal
Encoders with square-wave output signals can only be tested with a phase angle
measuring unit (PWM).