Rockwell Automation 1797-IRT8 FLEX Ex Thermocouple/RTD/mV Input Module User Manual - Manual (Page 57)

Publication 1797-6.5.2 - February 2001
Applying FLEX Ex Thermocouple/RTD/mV Input Modules 6-3
Select Protection
Method(s) The following table shows protection methods, method designation,
and how each provides protection. Although the FLEX Ex system
primarily uses the Intrinsic Safety protection method, the system uses
all methods listed below.
As not all protection methods are applicable for all locations, consult
local certifying agencies to determine acceptable protection methods
for your application.
Match Field Devices
and I/O Modules You must match field devices and I/O modules for your application to
function properly. Consider the following:
•
Verify field device and I/O module operational characteristics -
These characteristics will vary with sensor and application. For
example, RTD’s convert temperature to resistance change and
are generally slow responding devices. Is its resistance range
and speed appropriate for the module.
•
Match entity parameters of field devices and I/O modules - for
more specific information on matching entity parameters of field
devices and the 1797-IRT8 module are shown later in this
chapter.
1797-IRT8 and Thermocouple and RTD Functional and IS
Verification
Thermocouples and RTDs are available in a number of industry
standard types. These are generally designated by letter codes, such as
N, K, T, etc for thermocouples. The IRT8 is designed to work with a
variety of these types. Functional compatibility is simply a matter of
selecting the correct sensor type when configuring the IRT8 module
with the system I/O configuration software.
Table 6.A
Protection Methods for Hazardous Applications
Protection Method
Designation 1 Method of Achieving
Protection
Intrinsic Safety EEx
ia
/EEx
ib
Energy Limiting
Encapsulation EEx
m
Segregation
Increased Safety EEx
e
Refined Mechanical Design
FlameProof EEx
d
Containment
1 In the Non-Incendive protection method, n: used locally in the United States and United Kingdom.
In the Intrinsic Safety method, ia: Zone 0, 1, 2 & ib: Zone 1, 2