Intrinsic safety connections – Yokogawa 202 Field Mounting Rate Totalizer User Manual

Page 35

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Intrinsic Safety Connections

31

8. INTRINSIC SAFETY
CONNECTIONS

When installing the Model 202D in hazardous areas, the wiring and installation
must comply with appropriate installation standards.

The approval uses entity parameters on the input for connections to the flowmeter
and associated apparatus type approval for the 4-20mA output. The 4-20mA
output must, therefore, only be connected to barriers with the specified safety
parameters as shown on the following page.

8.1 COILS

The Model 202D will connect directly to a turbine flowmeter or paddlewheel with
a certified Intrinsically Safe (IS) coil or other certified IS sensor which produce a
pulse input provided they do not exceed the following input parameters:

Ui = 24V
Ii = 20mA
Pi = 320mW

The maximum allowed capacitance and inductance of the pulse or coil including
the cabling is:

Cext = 60

µ

F

Lext = 1.5H

The internal capacitance and inductance of the Model 202D seen on the input are
negligibly small with Ci = 0.02uF and Li = 0mH. The maximum voltage and
current produced by the Model 202D on its inputs (terminals 8 & 7) are:

Uo = 10.0V (open circuit)
Io = 9.0mA (short circuit)

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