welter worked as a civil servant for the ministry of the interior from july 1901 until october 1902 and for the ministry of colonial affairs in the kedu residency and pekalongan in the dutch east indies from october 1902 until april 1908 and in batavia from april 1908 until may 1911. welter moved back to the netherlands and worked for the ministry of colonial affairs in the hague from may 1911 until november 1915 and returned to the dutch east indies working for the ministry of colonial affairs in batavia from november 1915 until october 1925. after the election of 1925 welter was appointed as minister of colonial affairs in the cabinet colijn i, taking office on 1 october 1925. the cabinet colijn i fell just 3 months laste on 11 november 1925 and continued to serve in a demissionary capacity until the cabinet formation of 1926 with welters not giving a cabinet post in the new cabinet, the cabinet colijn i was replaced by the cabinet de geer i on 8 march 1926. in march 1926 welters was nominated as a , serving from 30 march 1926 until 30 march 1931. welter semi-retired from active politic and became active in the public sector served on several and councils on behalf of the government (cadastre agency, statistics netherlands and the welter commission) and as an diplomat and lobbyist for several economic delegations on behalf of the government. welter was elected as a member of the house of representatives after the election of 1937, taking office on 8 june 1937. following the cabinet formation of 1937 welter was appointed again as minister of colonial affairs in the cabinet colijn iv, taking office on 24 june 1937. the cabinet colijn iv fell on 29 june 1939 and continued to serve in a demissionary capacity until the first cabinet formation of 1939 with welters not giving a cabinet post in the new cabinet, the cabinet colijn iv was replaced by the cabinet colijn v on 25 july 1939. on 25 july 1939 just three days later cabinet colijn v was dismissed by queen wilhelmina and continued to serve in a demissionary capacity until the second cabinet formation of 1939 when it was replaced by the cabinet de geer ii with welter again appointed as minister of colonial affairs, taking office on 10 august 1939.