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Figure 3-3 Heidenhain SinCos encoder feedback signals
2.5Vdc
0Vdc
NOTE
Encoders are available which have a 1 V peak to peak voltage on sinref, sin, cos and cosref. This
results in a 2 V peak to peak voltage seen at the module's terminals. The drive will still function with
this type of encoder, however with reduced position resolution equivalent to four times the line rate.
(line rate = no. of lines per revolution x revolutions per second.) It is recommended that encoders of
this type are not used with a drive, and that the encoder feedback signals should meet the above
parameters (1 V peak to peak).
Sincos encoder resolution
The sine wave frequency can be up to 500 kHz but the resolution is reduced at high frequency.
Table 3-2 shows the number of bits of interpolated information at different frequencies and with
different voltage levels at the encoder port. The total resolution in bits per revolution is the ELPR
plus the number of bits of interpolated information. Although it is possible to obtain 11 bits of
interpolation information, the nominal design value is 10 bits.
Table 3-2 Interpolated information based on frequency and voltage level
Volt/Freq
1 kHz
1.2
11
1.0
11
0.8
10
0.6
10
0.4
9
SI-Universal Encoder User Guide
Issue: 2
0.25Vdc
COS
COS ref SIN ref
0.5Vdc
COS
5 kHz
50 kHz
11
10
11
10
10
10
10
9
9
9
SIN, COS signals
SIN
with respect to 0V
(offset at 2.5Vdc)
0.25Vdc
Differential signals
SIN
received by
SI-Universal Encoder
0.5Vdc
100 kHz
200 kHz
10
9
9
9
8
500 kHz
9
8
9
7
8
7
8
7
7
6
11
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