Proline Promass F 500 Modbus RS485 Electrical connection
Endress+Hauser 37
7 Electrical connection
NOTICE
The measuring device does not have an internal circuit breaker.
‣
For this reason, assign the measuring device a switch or power-circuit breaker so that
the power supply line can be easily disconnected from the mains.
‣
Although the measuring device is equipped with a fuse, additional overcurrent
protection (maximum 10 A) should be integrated into the system installation.
7.1 Connection conditions
7.1.1 Required tools
• For cable entries: Use corresponding tools
• For securing clamp: Allen key 3 mm
• Wire stripper
• When using stranded cables: crimper for wire end ferrule
• For removing cables from terminal: Flat blade screwdriver ≤ 3 mm (0.12 in)
7.1.2 Requirements for connecting cable
The connecting cables provided by the customer must fulfill the following requirements.
Electrical safety
In accordance with applicable federal/national regulations.
Protective ground cable
Cable: 2.1 mm
2
(14 AWG)
The grounding impedance must be less than 1 Ω.
Permitted temperature range
Minimum requirement: cable temperature range ≥ ambient temperature +20 K
Power supply cable
Standard installation cable is sufficient.
Signal cable
Modbus RS485
The EIA/TIA-485 standard specifies two types of cable (A and B) for the bus line which
can be used for every transmission rate. Cable type A is recommended.
Cable type A
Characteristic impedance 135 to 165 Ω at a measuring frequency of 3 to 20 MHz
Cable capacitance < 30 pF/m
Wire cross-section
> 0.34 mm
2
(22 AWG)
Cable type Twisted pairs
Loop resistance ≤110 Ω/km
Signal damping Max. 9 dB over the entire length of the cable cross-section
Shield Copper braided shielding or braided shielding with foil shield. When grounding
the cable shield, observe the grounding concept of the plant.
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