Baldor MN1928 4-12Input / Output, Baldor MicroFlex shown, 4.5.2.1Encoder input frequency, meters

4.5.2 Encoder inputs

The encoder inputs are available on pins a7-a10, b7-b10 and c7-c10. See section 4.2.1.

Two incremental encoders may be connected to NextMove ES, each with complementary A, B and Z channel inputs. Each input channel uses a MAX3095 differential line receiver with pull up resistors and terminators. Encoders must provide RS422 differential signals. The use of individually shielded twisted pair cable is recommended. See section 8.1.10 for details of the encoder power supply.

MicroFlex X7 encoder output

CHA+	1
CHA-	6

	NextMove ES
	Vcc
	10k
CHA+	b7
		to CPU
	120R	MAX3095
CHA-	b10
Twisted pair
DGND	a11 Connect internal shield to DGND.
Shield	Do not connect other end.
	a32
Connect overall shield to
connector backshells /
shield connections.

Figure 11 - Encoder channel input - typical connection from a servo amplifier

(Baldor MicroFlex shown)

4.5.2.1Encoder input frequency

The maximum encoder input frequency is affected by the length of the encoder cables. The theoretical maximum frequency is 20 million quadrature counts per second. This is equivalent to a maximum frequency for the A and B signals of 5MHz. However, the effect of cable length is shown in Table 3:

A and B signal		Maximum cable length
frequency
	meters		feet
1.3MHz	2		6.56
500kHz	10		32.8
250kHz	20		65.6
100kHz	50		164.0
50kHz	100		328.1
20kHz	300		984.2
10kHz	700		2296.6
7kHz	1000		3280.8

Table 3 - Effect of cable length on maximum encoder frequency

4-12 Input / Output MN1928