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4.3.
W
IRING
Wiring in non-explosive environments
1.
Take the device’s lid off.
2.
Put the cable through the cable gland (½" NPT) to the terminal block.
3.
Remove the outer insulation for ~80 mm (~3.15
″
) from the cable so the wires can be accessed, then strip the
wires for 4 mm. Strip the shielding from the signal cable.
4.
Connect the cable to terminal 2 and 3 (polarity is irrelevant).
5.
Retract the cable so the cable’s outer insulation runs through the cable gland for about 10 mm
(0.4
″
). Then
tighten the cable gland’s nuts with two wrenches.
6.
Organize the wires in the compartment.
7.
Put the lid back on.
Do not perform insulation tests with a test voltage of 500 V AC on the device due to the internal electronic
surge protection!
Connecting (grounding) to equipotential network (EPH)
Electrostatic discharge (E.S.D.)
Threaded earth connection (EP) on the side of the housing,
maximum wire cross section: 4 mm² (AWG12). The housing of
the device must be earthed to a ground with a resistance of
R
1 Ω.
The shield of the test lead must be earthed at the instrument
panel. Do not run the test lead near high-current cables, as
shielding does not provide protection against switching
harmonics.
The device is protected against 4 kV ESD.
Warning: The electrostatic discharge protection of the
measuring system cannot be solved by the internal ESD
protection.
In all cases, it is the user's responsibility to ensure that the
tank, measured material, and probe are grounded.
Risk of injury!
The probe may accumulate an electrostatic charge during
regular operation, so discharge it to the ground by touching
it (tank side) when installing!
Ground the inlet and the measured medium!
Design of the measuring network in non-explosive environments
Power supply
Nominal voltage
24 V DC
Maximum voltage (U
in
):
36 V DC
Minimal voltage (U
in
):
Depends on the impedance. (See diagram)
Loop resistance, R
loop
R
HART
+ R
cable
+ R
ammeter
Minimum R
HART
0 Ω
Maximum R
HART
750 Ω
R
HART
resistance for HART
®
communication
250 Ω (
recommended)
Line A: minimum voltage on the
device’s input terminals
Line B: minimum supply voltage (voltage drop on the device and the 250 Ω loop
resistance)
An example for calculating the supply voltage:
The minimum supply voltage at I
min
= 4 mA current:
U
supply min.
= U
in min.
+ (I
min
* loop resistance) = 12 V + (4 mA * 0.
25 kΩ) =
13 V
The minimum supply voltage at I
max
= 22 mA current:
U
supply min.
= U
in min.
+ (I
min
* loop resistance) = 11.5 V + (22 mA * 0.
25 kΩ) =
17 V
Therefore, if the loop resistance is 250 Ω, 17 V is just enough for the entire 4…20 mA
measuring range.
