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AD5933 Gain factor calculation

Question asked by pbillet@induct.be on Jan 10, 2012
Latest reply on Jan 10, 2012 by LiamR

Hi,

 

I'm trying to get started with the EVAL-AD5933EB. The results are not what I expected.

 

The settings I used:

USB PSU

Start freq 100Hz

Delta freq 100Hz

# incr 100

# settling times 15

MCLK 16M External clock provided on eval board

Range1: 2vp-p

Gain= X1

Resistor only R1 calibration

DDS X1

 

The following 4 measurements are performed:

1) "calculate gain factor" with 200K (on C41)  and then "start sweep"    Gain factor:5.109E-10       -> result = +- 200K

2) 99K1 (on C41) "start sweep"                                                                                                -> result = +- 113K  to high

3) "calculate gain factor" with 99K1 (on C41)  and then "start sweep"     Gain factor: 5.836E-10     -> result = +- 99K1

4) 200K (on C41) "start sweep"                                                                                                -> result = +- 170K  to low

 

I would expect that the gain factors would match?

 

Can somenone point me out what I'm doing wrong?

 

Many thanks

Philippe

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