SIEMENS
SINAMICS DCM
Engineering information
Characteristic values of the pulse tachometer
evaluation electronics
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Siemens D 23.1 · 2014
5
■
Overview
Input pulse levels
The evaluation electronics can process encoder signals
(symmetrical as well as asymmetrical) up to a maximum
differential voltage of 27 V. The encoder type is selected via
parameter. The evaluation electronics are adjusted electronically
to the encoder signal voltage. With the parameter setting, a sub-
division is made into two rated input voltage ranges.
If the pulse encoder does not supply any symmetrical encoder
signals, it must be grounded with each signal cable twisted in
pairs and connected to the negative connections of track 1,
track 2, and zero mark.
Maximum frequency that can be evaluated
The maximum encoder pulse frequency that can be evaluated is
300 kHz. To ensure the encoder pulses are evaluated correctly,
the minimum edge clearance
T
min
between two encoder signal
edges (track 1, track 2), as listed in the table, must be adhered
to.
If the pulse encoder is incorrectly matched to the encoder cable,
disturbing cable reflections will occur at the receiving end. To
ensure that encoder pulses of this type can be evaluated without
errors, these reflections need to be damped. The limit values
listed in the table below must be maintained in order to prevent
the resulting power losses in the evaluation electronics adaptor
from being exceeded.
Cable, cable length, shield connection
The encoder cable capacitance must be recharged at each en-
coder edge change. The rms value of this current is proportional
to the cable length and pulse frequency, and must not exceed
the current permitted by the encoder manufacturer. A suitable
cable that meets the recommendations of the encoder manufac-
turer must be used, and the maximum cable length must not be
exceeded.
Generally speaking, a twisted cable pair with a single pair shield
is sufficient for each track. This reduces crosstalk between the
cables. Shielding all the pairs provides protection against
interference pulses. The shield should be connected to the
SINAMICS DC MASTER shield bar through a large surface area.
Rated input voltage range
5 V
15 V
Low level
Differential voltage < 0.8 V
Differential voltage < 5 V
High level
Differential voltage > 2 V
Differential voltage > 8 V
1)
Hysteresis
> 0.2 V
> 1 V
Common-mode controllability
±
10 V
±
10 V
Rated input voltage range
5 V
15 V
Differential voltage
2)
2 V
> 2.5 V
8 V
10 V
> 14 V
T
min
3)
630 ns
380 ns
630 ns
430 ns
380 ns
F
max
50 kHz
100 kHz
150 kHz
200 kHz
300 kHz
Differential voltage
4)
Up to 27 V
Up to 22 V
Up to 18 V
Up to 16 V
Up to 14 V
1)
Restriction: See "Maximum frequency that can be evaluated"
2)
Differential voltage at the terminals of the evaluation electronics
3)
The phase error
L
G
(deviation of 90°) that may occur caused by the
encoder and cable can be calculated from
T
min
:
L
G
= + (90° –
f
p
×
T
min
×
360°
×
10
-6
)
L
G
Phase error in °
f
p
Pulse frequency in kHz
T
min
Minimum edge clearance in ns
4)
Differential voltage of the encoder pulses without load (approximate
encoder power supply voltage)
© Siemens AG 2014