Calculation Of The Remaining Supply Voltage At The Sensor - Siemens SIMATIC 6DL1 136-6AA00-0PH1 Manual

Applications of the F-I/O module

6.11 Calculation of the remaining supply voltage at the sensor

6.11 Calculation of the remaining supply voltage at the sensor
To ensure the function of the connected sensor, the remaining supply voltage U
greater than/equal to the minimum supply voltage of the sensor.
To calculate the remaining supply voltage on the sensor, determine the following voltages
depending on the wiring scheme used:
• Determine the minimum supply voltage (UV
Power supply unit e.g. for SITOP 24 V ± 2%
UV
(Voltage drop on the supply line to the I/O module was neglected).
• Calculate the maximum voltage drop on the signal line (U
For example, for copper cable 500 m with ∅ = 0.5 mm²; at I
U
• Calculate the voltage drop (U
– With Ri
– In a high-availability application case, the voltage of the Z diodes used in the redundant
• Determine the voltage drop at the sensor supply U
U
Calculation examples
Example for the calculation of the remaining supply voltage (U
application case with no high-availability:
• U
• U
Example for the calculation of the remaining supply voltage (U
application case with high availability:
• U
• U
60
= UV – [Tolerance] = 24 V – 2% = 23.5 V
min
= 35.7 Ω × 25 mA = 0.9 V
line
= 150 Ω; at I
max
U = 150 Ω × 25 mA = 3.8 V
Ri
terminal block (U = 6.2 V) must also be considered with a tolerance of 5%.
Z
U = U + Tolerance = 6.2 V + 5% = 6.5 V
Z_6V2 Z
= 1.2 V
sensor supply
= UV – U – U – U
min min line Ri
= 23.5 V – 0.9 V – 3.8 V – 1.2 V = 17.6 V
min
= UV – U – U
min min line Z_6V2
= 23.5 V – 0.9 V – 6.5 V – 3.8 V – 1.2 V = 11.1 V
min
):
min
) at the input resistance "Ri" of the I/O module:
Ri
= 25 mA
max
sensor supply
– U – U
Ri sensor supply
):
line
= 25 mA
max
:
sensor supply
) on a 2-wire transmitter in an
min
) on a 2-wire transmitter in an
min
F-AI 8xI 2-/4-wire HART HA
Equipment Manual, 09/2021, A5E50557845-AA
must be
min