PGA970: 4-wire LVDT phase readout not working

Hi,

I'm using the PGA970 LVDT signal conditioner on a PGA970EVM evaluation board togeter with a USB2ANY board to read out the data.

I have connected the 4-wire LVDT in the following way:

I use the PGA970 GUI to program the chip and capture data. The amplitude signal works as expected, going to zero when the LVDT is at its central position and increasing when it is moved in either direction. However, the phase signal is always at 45 degree with noisy fluctuations in the range +/- 1 degree. The phase signal should change strongly around the central LVDT position to distinguish, wheather the LVDT is moved up or down.

Could my PGA970EVM board be broken or am I  missing something?