The MTL4021S enables an on/off device in a hazardous area to be controlled by a volt-free contact or logic signal in the safe area. It can drive loads such as solenoids, alarms, LEDs and other low power devices that are certified as intrinsically safe or are classified as nonenergy storing simple apparatus. Provided that 24V dc is applied to the override input, the solenoid/alarm can be operated by the control
input. However, if the 24V dc signal is removed, the solenoid/alarm is turned off. Earth fault detection can be provided by connecting an MTL4220 earth leakage detector to terminal 6.

Override Input

– – A 24V logic signal applied across terminals 8 and 9 allows the solenoid/alarm to be operated by the control input. If it is disconnected, the solenoid/alarm is off.

Power requirement, Vs

– – 100mA at 24V dc

– – 120mA at 20V dc

– – 75mA at 35V dc

Power dissipation within unit

– – 1.3W with typical solenoid valve, output on

– – 1.9W worst case

Isolation

– – 250V ac between safe- and hazardous-area
circuits.