MICRONOR AG
MR340-1 DIN Rail Module Controller
Page 43 of 74
Voltage Filter (Register 0x203)
Register Address: 0x203
A user configurable low pass filter exists to allow smoothing of the calculated RPM based on
user constants. It is the filtered RPM that is output to the voltage DAC. The 3dB filter point is
programmable from 500Hz (no filtering) down to 1Hz
Af
: Filtered analog output value
Af [t-1]
: Previous filtered analog output value
n
: filter constant in2n milliseconds
Am
: new analog (unfiltered) value
The analog output is updated every 1ms thus when setting the filter value to n an
approximate time constant of n ms can be expected. The MR320 measures the period
between passing slits of the code wheel. When the encoder is turning slow so that the
elapsed time between slits is larger than 1ms then the low pass algorithm is changed and the
time constant becomes larger as the encoder turns slower. This adaptive filtering algorithm
provides for a smooth output signal change.
If no filtering is desired, simply turn the filter OFF by setting it to value 0.
When in position mode, it is recommended not to use the filter.
MODBUS commands:
Address Register Description
Access
0x200
1
Voltage Mode
Read/Write
0x201
2
Voltage Scale
Read/Write
0x203
1
Voltage Filter
Read/Write
(A
f [t-1]
* 2
n
-1) + A
m [t]
2
n
A
f
=