Michell Instruments Easidew PRO, User Manual

Page: 9 / 58

I.S. Field Display User’s Manual
Michell Instruments 3
INSTALLATION
2 INSTALLATION
2.1 4-20 mA Input
The input safety parameters for the two 4-20 mA input terminals 1 & 3 are:
Ui = 30 V DC
li = 200 mA
Pi = 0.84 W
The maximum equivalent capacitance and inductance between the two 4-20 mA input
terminals 1 & 3 is:
Ci = 13nF
Li = 16 μ H
The maximum permitted loop cable parameters can be calculated by adding these
fi gures to
Ci
and
Li
of other instruments in the loop and subtracting the totals from the
maximum cable capacitance
Co
and cable inductance
Lo
permitted for the Zener barrier
or galvanic isolator powering the loop.
Although the I.S. Field Display does not itself comply with the requirements for
simple apparatus, the EC-Type Examination Certi fi cate states that for intrinsic safety
considerations, under fault conditions, the output voltage, current and power at
terminals 1 & 3 will not exceed those speci fi ed by clause 5.7 of EN 60079-11 for simple
apparatus. This simpli fi es the application and documentation of intrinsically safe loops
containing the I.S. Field Display.