Hi Maveen,
Zitat:I couldn write 5 v in digital port output is not coming.
DIO usually work with boolean signals (FALSE/TRUE)...
Zitat:so i want to give 4v signal from DIO to the relay.
DIO ports usually work with standard logic levels like 5V or 3.3V. Which one your Meilhaus1208 supports is described in the manual...
I suppose it uses 5V logic levels. So you could use a voltage divider (with two resistors) - but you should also consider the current draw of your relais to setup the divider correctly. Instead of a divider a simple diode (preferrably Si diode with a threshold voltage of ~0.7V) may also be used in series to the relais to reduce voltage over your relais...