The new variable period undulator with unique design was developed and built recently at Budker INP. It will replace the electromagnetic undulator being used now at the second FEL of the Novosibirsk FEL facility. As the result the FEL tunability range will be substantially increased. In this paper we present the results of the undulator magnetic field measurements for different periods as well as discuss the ways to reduce field errors which include magnets sorting, weakening of undulator edge poles and using of steering coils. Results of researches supported by RBRF grant 15-02-07776 were used in this work.