Incremental encoders, input pulse levels

The evaluation electronics can process encoder signals (symmetrical as well as asymmetrical) up to a max. 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 incremental 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.

Incremental encoder, maximum frequency that can be evaluated

The max. frequency of the encoder pulses 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 incremental 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.

Incremental encoder, cable, cable length, shield support

The encoder cable capacitance must be recharged at each encoder 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 manufacturer must be used, and the max. 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 Cabinet shield bar through a large surface area.

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°), caused by the encoder and cable and which is permissible, can be calculated from T_min:
L_G = + (90° - f_p Г— T_min Г— 360° Г— 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)