def before_pass(pass_no, scan):
    print pass_no
    if pass_no ==  scan.numberOfPasses:
        pass
#sensor.setTrustedMonitor(False)
#sensor.setForcedRead(True)
cscan([dks], [dks.readback], [15.0], [17.0], [0.1], latency=0.0, time=3.0, relative=False, passes=2, zigzag=True, name='test', \
       before_pass = before_pass )