Normally open type
Check connection between terminals.
There must be a connection between terminals No. 1 and No. 2 if the power and «weight» connected to terminals No. 3 and No. 4, respectively.
There should be no connection between terminals No. 1 and No. 2 if the power is disconnected.
5 terminal type
Check connection between terminals.
There must be a connection between terminals No. 1 and No. 2 if the power and «weight» connected to terminals No. 3 and No. 5, respectively.
The connection must be between terminals No. 1 and No. 4 if the power is disconnected.