FM355-2 S

[a151218 0]

I use FM355-2S module,When the DO is off ,I measure tht DO voltage.There is DC16V.When the DO is ON,I measure tht DO voltage.There is DC24V.But there is 16V output when DO is off,My contact always on.I have 3 FM355-2S ,The status of every FM355-2S is the same.Anyone can tell me how to solve the problem .....thx