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Encoder Interface UVW / TTL Output
.2.2.2
Position evaluation
The levels of the U, V ,W signals are measured after switching on and thus the absolute po-
sition of the encoder is determined within an electrical revolution of the motor (= el. revolu-
tion of the absolute tracks UVW). This position can maximally vary with 0° of the electrical
revolution. The current position is first set to this start position.
If the motor starts to turn and the first rising edge at the U, V or W track is overdriven, the
exact absolute position is determined and the current position is corrected to this value.
Only the rising edge of the W track is evaluated for the position correction during normal
operation.
The zero signal is not evaluated for position correction and positioning. Only the encoder
breakage recognition uses the error signal of the track. If the zero signal is not recognized
during the initialization of the encoder, it is considered as not connected.
The pole-pair number of motor and encoder (the periods of the UVW tracks) must be
equal.
After switching on the pole-pair number and the number of increments of the encoder are
examined with the adjustments of the control board. During the first revolution of the enco-
der the number of increments per revolution and the periods of the UVW tracks are taken
in account and after this revolution it is decided whether the adjustment corresponds to the
encoder. The interface status displays value 70 if this is not the case.
.2.2.
Encoder breakage recognition channel 1
For a monitoring of the encoder and the encoder cable to channel 1 each signal track is
monitored. The monitoring is switched on/off with parameter Ec.42 (Ec.20 up to V2.8). The
recognition of encoder breakage triggers an „error! encoder change" (value 5), if the vol-
tage between two signal pairs is smaller than 625mV. Value 68 is displayed in parameter
Ec.7 "enc.1 encoder status".
.2.
Encoder line length
Maximum encoder line length corresponding to the voltage drop caused by the cable resis-
tance:
The maximum line length is additionally limited by the encoder frequency and cable capa-
city.
.2.4
Tested encoders
The following encoders have been tested by KEB on it application:
•
Heidenhain ERN 42
However, this does not restrict the use of rotary encoder with same specifications of other
manufacturers.
Encoder cable length =
max. encoder current I
Encoder voltage U: Voltage output
min. signal voltage U
e.g. encoder cable resistance R: 0,06 Ω/m at 0,5 mm²
U - U
min
––––––––––
I
• 2 • R
max
: see encoder description
max
: see encoder description
min
GB-9
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