Reference Instruction Manual

EF[N] - Encoder Filter Frequency
Purpose:
Filters encoder signal in order to improve its noise immunity. Because the logic of the
quadrature decoder must sense transitions, the inputs are first run through a glitch
filter. This filter has a digital delay line that samples one, three, or six time points on
the signal and verifies that all of the samples are at a new state before outputting the
new state to the internal logic. The sample rate of this delay line is programmable, to
adapt to a variety of signal bandwidths.
When an analog encoder is used, the basic signal, before interpolation, is filtered using
the same method.
EF[N] sets the sample rate of the corresponding digital glitch filter: EF[1] for the main
encoder and EF[2] for the auxiliary encoder. If EF[N] is zero the digital filter is
bypassed.
If EF[N] is large, the encoder reading noise immunity will be better, but true fast
transitions (occurring by fast speed) may be dismissed as false. A number that is too
small may cause the counting of noise pulses.
The formula for calculating EF[N] is
7
10
[]
max expected speed in counts/second
EF N =
.
Example:
Suppose that the maximum speed of a motor is 1000 rpm and that the motor is
equipped with an encoder with 1000 lines (4000 counts/rev with resolution
multiplication). The expected speed is
5
1000
6.67 10 / sec
60se
4000 /
c/ min
coun rpm
count
trev×
=×
and we set
7
10
[1] 15
667500
EF =≈
Notes:
• When an interpolator is used, the time difference between consecutive
signal changes may sometimes be much shorter. This is dictated by the
interpolator’s specifications and not by the motor speed.
• When working with an analog encoder, always set EF[1]=18.
Attributes: Type: Parameter, Integer
Source: Program, RS-232, CANopen
Restrictions: None
Default values: 0 (RS), Non-volatile
Range: [0...127]
Index range: [1, 2]
Unit modes: All
Activation: Immediate
SimplIQ: Modified
SimplIQ for Steppers Command Reference Manual Alphabetical Listing
MAN-STECR (Ver. 1.1)
57