subroutine test_amp(plane, dc)
  use nonlin_bpm_mod
  use precision_def
  implicit none

  type(cesr_det_plane_struct), intent(inout) :: plane(0:n_det_maxx)
  type (cesr_det_dc_position_struct) dc(0:n_det_maxx)

  integer :: det, i,ir
  real(rp) long_cos(4), long_sin(4), ccos, ssin
  real(rp) deg_to_rad
  logical orig_offsets, orig_rotation



deg_to_rad = twopi/360.
i=0
do det = 0,n_det_maxx
     if (all(plane(det)%but(:)%amp .lt. 1e-10)) then
        if (det < 100) print *, "All amplitudes are zero for detector",det
        plane(det)%x%amp = 0.
        plane(det)%y%amp = 0.
        plane(det)%x%phase = 0.
        plane(det)%y%phase = 0.
    else

  if(plane(det)%system_id < 1)cycle    
!  ir = u%db%detector(det)%ix_lat
!  if(ir == 0)cycle
  if(any(plane(det)%but(1:4)%amp < 1.e-10))cycle 
  i=i+1
  long_cos(1:4) = plane(det)%but(1:4)%amp * cos(plane(det)%but(1:4)%phase * deg_to_rad)
  long_sin(1:4) = plane(det)%but(1:4)%amp * sin(plane(det)%but(1:4)%phase * deg_to_rad)
  ccos = long_cos(4)-long_cos(3)+long_cos(2)-long_cos(1)
  ssin = long_sin(4)-long_sin(3)+long_sin(2)-long_sin(1)
  plane(det)%x%amp = sqrt(ccos**2 + ssin**2)
  plane(det)%x%phase = atan2d(ssin,ccos) 

  ccos = long_cos(4)+long_cos(3)-long_cos(2)-long_cos(1)
  ssin = long_sin(4)+long_sin(3)-long_sin(2)-long_sin(1)
  plane(det)%y%amp = sqrt(ccos**2 + ssin**2)
  plane(det)%y%phase = atan2d(ssin,ccos) 

 endif

end do

end