The MTL2220 continuously monitors floating electrical circuits in a hazardous area, and warns if their resistance to earth falls below

10kΩ. It enables other MTL2000 and 3000 Series units to be used in the ‘no-fail’ mode, whereby earth faults on field lines can be

detected and rectified without upsetting control or needing emergency action. The measuring circuit of the unit uses a 1Hz oscillator, amplifier and phase-sensitive demodulator to reject electrical interference up to 250V. A self-test facility enables the unit to be checked automatically or manually from time to time to ensure the integrity of the whole system. Testing is carried out by connecting two safe-area terminals together; this triggers an IS opto-coupler to connect a known resistance across the input terminals, de-energising the relay and LED if the unit is healthy, but having no effect on the monitored circuits. The changeover output contacts are duplicated within the unit for reliability.

 

MTL2000 series

Product CodeDescription

MTL2210B  Switch operated relay ~ 1-channel

MTL2211  Switch operated relay ~ 2-channel 

MTL2213  Switch/proximity detector relay ~ 3-channel 

MTL2215  Switch operated relay ~ IS output

MTL2220  Earth-leakage detector 

MTL2241  Solenoid/alarm driver ~ 1-channel 

MTL2242  Solenoid/alarm driver ~ 4-channel

MTL2313  Trip amplifier ~ general purpose

MTL2314  THC trip amplifier

MTL2315  RTD trip amplifier

MTL2316  Bonding integrity monitor 

MTL2441B  4/20mA Repeater power supply

MTL2442B  4/20mA Isolating driver