A high voltage pulser up to 50 kV, with a main pulse of 2 s time duration, was realized using a fast high voltage capacitor of 150 nF (50 kV) connected to the ground by a homemade spark-gap. The circuit, contained in a metallic box, had short electric connections in order to reduce any stray inductances. The diagnostics was performed by two systems: an auto-integrating Rogowski coil and an integrator connected to a current transformer, both suitable for pulses longer than 1 s. In order to get the above characteristic the Rogowski coil circuit must have a ratio L/R higher than 1 s, while the integrator, formed by a resistance and a capacitance, must get the product RC higher than 1. In the first system, the load resistance can be easily reduced, instead it is very difficult to reduce the coil resistance. The Rogowski coil we build exhibited a ratio L/R= 2 s, while the integrator circuit connected to the transformer exhibited a value RC= 5 s. We made a solenoid with an inductance of 2.8 H (11 rings, length 14 cm) which was fed by the current generated by the pulser up to 4 kA, 1 s at 24 kV of charging voltage. Under the above conditions, we estimate a magnetic field of 0.4 T applying the Ampere law. Actually, the magnetic field was measured in dc mode by means of a Hirst GM07 gauss-meter having a conversion coefficient of 0.08 mT/A which determined a magnetic field at the center of 320 mT. Potentially, at the maximum voltage of 50 kV we can get a magnetic field up to of 0.7 T.