Toshiba E6580772 instruction manual Selection of encoder type, １００ｍ

E6580772③

★Caution in case of using open collector encoder connection

In case using pulse command oscillator and open collector encoder, the rise time of the voltage when the transistor is OFF tends to be longer than the fall time at the time when the transistor is ON. Therefore, if the maximum input frequency becomes higher, the pulse duty cannot maintain the 50±10% specification. Conduct derating on the maximum input frequency so that the pulse duty will be within the following specification range.

<Derating computation formulae of open collector’s maximum input pulse frequency >

0.8／(Maximum input frequency x A) – Voltage rise time ≧ 3 x 10 –6…..①

A : (single phase input: 2) (two-phase input: 4)

Voltage rise time ＝ Encoder exclusive pulse rise time + R x C

Encoder exclusive pulse rise time (s) : Please inquire at the encoder manufacturer.

R (Ω) (Input resistance)		: internal resistance 1000(Ω)＋external resistance value
		(In case there is external resistance)
C(F) (Cable static capacity)		: Please inquire at the cable manufacturer.
<Example>
Encoder	: LBJ-005-500 (SUMTAK), 2-phase input
	Encoder pulse rise time : 0.35 x 10-6(s)
Cable	: ROVV-SB-0.2-5P-10m (Furukawa Electric Co., Ltd)
	Static capacity : 120 x 10 –12(F/m) x 10 (m)

From Formulae①

0.8／(Maximum input frequency x A) – Voltage rise time ≧ 3 x 10 –6Voltage rise time = (0.35 x 10 –6) + 1000 x (120 x 10-12x 10)

= 1.55 x 10-6

[Maximum input frequency] ≦87912 (Pulse/s) [Single phase input] ≦43956 (Pulse/s) [Two-phase input]

3.2.3 Selection of encoder type

The encoder type should be selected, following the table below.

Encoder Type	Characteristics	Maximum Wiring Length
	Rated voltage output with emitter/follower
	combination.
Complementary	High anti-nose characteristics. High-speed response.	１００ｍ
	Long-distance transmission capability.
	Need to pay attention to waveform irregularity.
	The collector of the transistor is output directly.
Open Collector	Low anti-noise characteristics. Low-cost.	１０ｍ
	Need to pay attention to waveform irregularity and
	distortion.

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