Micromod MOD: MODCELL Multiloop Processor 2002N Model C and Associated Hardware User Manual
Page 44
MODCELL Multiloop Processor
ELECTRICAL CONNECTIONS
S-3031-29
Figure 3-
7
. Typical Input Circuit for 2009A RTD Input Module
I
NC
S20
14
2
1
Ref
Ref
3-Wire
RTD
S19
A/D
BASE INSTRUMENT
LOWER
TERMINAL
HOUSING
2009AZ__2__ RTD INPUT MODULE
(Module Location 19)
DATA
Processor
SEL
CLK
GND
+5V dc
Input
Isolation
+10V Iso
3
6
4
7
5
2
1
A
B
1
2
2009AZ__1__ RTD INPUT MODULE
(Module Locations 20 and 21)
DATA
Processor
SEL
CLK
GND
+5V dc
Input
Isolation
+10V Iso
3
6
4
7
5
A/D
2
1
S21
Comp
1
2
2-Wire
RTD
I
L/W
Compensation
NOTE: The lead wire resistance effect is about +0.001
Ohm
/
Ohm
(ohms per lead).
Assuming 20 ohms per lead, the total error could be calculated as follows:
Error = ((0.001
Ohm
/
Ohm
× 20
Ohm
/lead) ÷ 400
Ohm
Module Span) × 100%
= 0.005%
The RTD sensor used for cold junction compensation is a platinum 1000 ohm RTD with an
alpha of 0.00385. The sensor is Class B (0.12%) and has an operating temperature range
of –50°C to +650°C (–58°F to +1202°F). It is connected to a 2 wire RTD input module
and installed in the housing.
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