Scintillation observations of strong northern pulsars

Scintillation of pulsar radio emission provides information about the inter stellar medium along the path to the pulsar and the velocities of pulsars. It also affects the precision of pulse timing observations. Using a pulsar timing system developed at the Urumqi Astronomical Observatory 25 m telesco pe, we observed diffractive scintillation dynamic spectra for several stron g northern pulsars. This paper introduces the observing system and discusse s the observational results.