Level of input pulses

The evaluation electronics are capable of processing encoder signals (both symmetrical and asymmetrical) up to a maximum of 27 V differential voltage. The evaluation electronics are electronically adapted (in Parameter P140) to the encoder signal voltage. The parameter setting selects one of two possible rated input voltages (see table 4)

If the pulse encoder does not supply symmetrical encoder signals, then its grounding lead must be routed with each signal cable as a twisted pair and connected to the negative terminals of Track 1, Track 2 and the zero marker (see table 5)

Table 4
Explanation of terms

Table 5
Minimum distance between edges

Table 6
Maximum input frequency as a function of supply voltage

Switching frequency

The maximum frequency of the encoder pulses is 300 kHz. To ensure correct evaluation of the encoder pulses, the minimum distance Tmin between two encoder signal edges (Tracks 1 and 2) specified in the table must be observed.

If the pulse encoder is incorrectly matched to the encoder cable, disturbing cable reflections will be produced at the receive end. These reflections must be damped so that the encoder pulses can be correctly evaluated. The limit values specified in Table 6 must be maintained to ensure that the resultant power loss in the adapting element of the evaluation electronics is not exceeded.

Cable, cable length, shield connection

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 specified by the encoder manufacturer. A suitable cable as recommended by the encoder manufacturer must be used and the maximum cable length must not be exceeded.

Generally, a twisted-pair cable with a common pair shield is sufficient for each track. Crosstalk between the cables is thus reduced. The shielding of all pairs protects against noise pulses. The shield must be connected to the shield bar of the SIMOREG converter over the largest possible surface area.

1) Restriction: See switching frequency

2) Differential voltage at evaluation electronics terminal

3) The phase error LG (deviation from 90°), which may occur as the result of encoder and cable, can be calculated from T_min
L_G = + (90° – fp x T_min x 360° x 10–6)

L_G [°] = phase error

f_p [kHz] = pulse frequency

T_min [ns] =Minimum distance between edges

4) Differential voltage of encoder pulses without load (approximate encoder current supply voltage)