Endress+Hauser Prothermo NMT81 - Hardware Locking or Unlocking

Prothermo NMT81 Electrical connection
Endress+Hauser 49
6.2 NMT81 transmitter and element connection
Four-wire common return enables the highest accuracy in the narrowest probe in a limited
tank nozzle opening. The wiring diagram shows the configuration as follows.
A
3
4
3
2
1
3 4
a
b
A0042780
 33 Four-wire connection diagram
A Sensor unit
a Current flow
b Voltage measurement
1 Connector 1
2 Connector 2
3 Connector 3
4 Connector 4
6.3 NMS8x/NMR8x/NRF81 (Ex d [ia]) intrinsically safe connection
To connect an intrinsically safe NMT81, E1 and E2 are used to connect with NMS8x, NMR8x
and NRF81.