cui.com

date 03/29/2013

│ page 5 of 6

CUI Inc

│ SERIES: AMT303 │ DESCRIPTION: MODULAR ENCODER

ENCODER OPERATIONAL MODE

Initialization mode:

– At power up the encoder goes through an initiation and stabilization procedure. This includes

microprocessor stabilization and the program for combining Coarse and Fine channel of the encoder for

getting the absolute start position. This takes less than 0.1 seconds.

Tracking mode:

– MCU 12 bit position register is updated from Fine Asic every 48 μs.

– The commutation program in the MCU has a compensation for the average delay caused by the update

rate, leaving a remaining jitter of less than 24 µs RMS.

•The communication jitter expressed in electrical degrees will be proportional speed and

does not reach 6 deg RMS until the speed reaches the following values:

COMMUTATION ALIGNMENT AND SETTING THE ZERO POINT

We strongly recommend the use of the AMT303 series demo board to set commutation zero. It greatly

simplifies and expedites the process. The demo board also allows setting of resolution, # of motor poles,

direction of quadrature increment, and commutation angle offset (when required). If you do not have or

cannot obtain a demo board, use the following procedure to align the AMT303XX commutation angle with your

motor:

1.

Mount the AMT303 series encoder to the motor.

2.

Put the motor in a ‘locked rotor’ condition. Consult your motor manufacturer if you are not certain how to lock the

rotor for commutation alignment.

3.

With the motor in a locked rotor position, pull pin# 2 (zero set) low, tie Pin 2 to Ground, to write the rotor position

into non-volatile memory in the encoder.

4.

Power cycle the encoder, i.e., remove power from it. The commutation position is now permanently aligned with

the motor rotor zero position and will use this offset at initialization every time at startup.

Note: The procedure is based on the standard “WYE” motor phase connection configuration. If your motor uses

other than the “WYE” phase connection, you must acquire the AMT303 series demo board to program the

required offset to align encoder commutation signal zero with motor zero position.

0

2

4

6

8

10

12

14

0

2000

4000

6000

8000

10000

RPM

Commuta on Ji er in Electrical Degrees

4 pole

6 pole

8 pole

10 pole

12 pole

20 pole