+15V
2
10.0V
Thermocouple
R
1
27kΩ
R
4
+15V
6
REF102
4
+15V –15V +15V –15V
Isothermal
Block with
1N4148
(1)
R
G
1MΩ
R
2
2
7
+In
1
8
INA114
or
INA128
–In
4
3
R
3
100Ω
R
5
50Ω
–15V
R
6
100
Zero Adj
ISA
TYPE
E
6
5
15
1
2
9
10
8
16
7
V
OUT
ISO124
MATERIAL
Chromel
Constantan
Iron
Constantan
Chromel
Alumel
Copper
Constantan
SEEBACK
COEFFICIENT
(µV/°C)
58.5
50.2
39.4
38.0
R
2
(R
3
= 100Ω)
3.48kΩ
4.12kΩ
5.23kΩ
5.49kΩ
R
4
(R
5
+ R
6
= 100Ω)
56.2kΩ
64.9kΩ
80.6kΩ
84.5kΩ
Ground Loop Through Conduit
NOTE: (1) –2.1mV/°C at 2.00µA.
J
K
T
FIGURE 6. Thermocouple Amplifier with Ground Loop Elimination, Cold Junction Compensation, and Up-scale Burn-out.
13
0.8mA
0.8mA
R
G
4
2
RTD
(PT100)
R
Z(1)
R
CM
1kΩ
3
1
14
10
0.01µF
7
4-20mA
+V
S
= 15V on PWS740
16
3
15
15
1
14
2
RCV420
5, 13
10
4
11
12
ISO124
+V
9
7
8
10
2
16
–V
Gnd
–V
S
= –15V
on PWS740
XTR105
6
V
OUT
0V - 5V
1.6mA
NOTE: (1) R
Z
= RTD resistance at minimum measured temperature.
FIGURE 7. Isolated 4-20mA Instrument Loop. (RTD shown.)
®
9
ISO124
BURR-BROWN [ BURR-BROWN CORPORATION ]
