Technical data testo 6740 without alarm plug
Electrical connectiontesto 6740 without alarm plug 
| Terminal | Terminal allocation |
|---|
| 1 | + (4 to 20mA, supply 12 to 30 VDC) | | 2 | - (4 to 20mA) | | 3 | not used | | 4 | Measurement earth (cable shield) |
Technical data testo 6740 with alarm plug (0554.3302)
Electrical connectiontesto 6740 with alarm plug (0554.3302) 
| Terminal plug socket | Terminal allocation plug socket |
|---|
| 1 | I +(4 to 20mA) A | | 2 | I - (4 to 20mA) B | | 3 | (connected to the relay board ex-works) | | 4 | Connect shield |
as well as | Terminal relay board | Terminal allocation relay board |
|---|
| 1 | 20 to 28 VDC A | | 2 | LS + | | 3 | LS - | | 4 | US + | | 5 | US - | | 6 | 0 VDC B |
The supply connections must be connected galvanically, i .e. A-A or B-B! 
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