Axis 670 Manual de Instruções descarregar pdf (Página 55)

e) Adjust the signal generator for about 200mV peak on current. This is a ballpark

> figure. The main concern is that the current through the coil be large enough to view

with good S/N ratio, but small enough to avoid excessive coil heating and mechanical

vibration ofthe scanner while performing this test. Maintain the position signal near

0 volts by adjusting the DC offset control ofthe function generator accordingly.

f) Slowly sweep

frequency

up while observing position and current on scope. Note the

frequency where a peaking occurs in the position and/or current waveform. This is Fr.

You can also hear the scanner become louder at Fr as well. When Fr is identified,

keep the signal generator at this

frequency

and shut it off promptly, as

well

as board

power. Bearing wear will result if the scanner is held at the resonant frequency for

too long.

6.2.2.2. Selecting the proper 6740-xx NFM

The 6740-xx NFM's come in six different frequency ranges:

6740-06

6740-05

6740-04

6740-03

6740-02

6740-01

12.5-20 Khz

7-14 Khz

5-10 Khz

3.7-7.5

Khz

2.2-4.5

Khz

1.6-3.4

Khz

Select the proper NFM for the Fr measured in step (If) above. Choose one which the measured

Fr is closest to the center ofthe range.

6.2.23.

Inserting and tuning the 6740-xx NFM

Make sure

tiiat

the 670 board is completely de-tuned. This section ofthe procedure will not work

otherwise.

a) Insert the NFM with its solder side facing the 670 heatsink bracket.

b) Connect TP4 to ground via jumper

clip.

This open circuits the output amp so that it will

not

driving the scanner during

NFM

adjustment

c) Connect the signal generator to

TP5.

This is the summing amp input. Connect the scope

probe to

TP6.

This is the NFM output.

d) Tum on the signal generator and observe the NFM output on the scope. The signal

generator should still be set at the resonant

frequency

from

the previous measurement.

This is very important, since the NFM has a sharp attenuation characteristic. If the

frequency that the NFM is being tuned to reject is not exactly at the Fr ofthe scanner and

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