DATAFORTH
A Burr-Brown Company
®
50
Call 800-444-7644
For Information and Assistance
SCM5B34
Linearized 2- or 3-Wire R TD Input Modules
FIGURE 1. SCM5B34 Block Diagram.
The SCM5B modules are designed with a completely isolated computer
side circuit which can be floated to ±50V from Power Common, pin 16. This
complete isolation means that no connection is required between I/O
Common and Power Common for proper operation of the output switch. If
desired, the output switch can be turned on continuously by simply
connecting pin 22, the Read-Enable pin to I/O Common, pin 19.
RTD excitation is provided from the module by two matched current
sources. When using a three-wire RTD, this method allows an equal current
to flow in each RTD lead, which cancels the effects of lead resistances. The
excitation currents are very small (0.25mA for 100Ω Pt and 120Ω Ni, and
1.0mA for 10Ω Cu) which minimizes self-heating of the RTD.
Signal filtering is accomplished with a six-pole filter which provides 95dB
of normal-mode-rejection at 60Hz and 90dB at 50Hz. Two poles of this filter
are on the field side of the isolation barrier, and the other four are on the
computer side. After the initial field-side filtering, the input signal is
chopped by a proprietary chopper circuit. Isolation is provided by trans-
former coupling, again using a proprietary technique to suppress transmis-
sion of common mode spikes or surges. The module is powered from
+5VDC, ±5%.
A special input circuit on the SCM5B34 modules provides protection
against accidental connection of power-line voltages up to 240VAC.
LPF
3 and 4 Wire
(1)
2 Wire
+In
–In
RTD
–EXC
4 Wire
(1)
Backpanel
Term Block 1
2NC
4
6
5
3
NC
Surge
Suppression
and
Protection
Isolated
Field-Side
Power
4
3
2
1
+EXC
R
Z
–V
+V
–V –V
NOTE: (1) 4-wire sensors may be
used with this module. However,
for true 4-wire measurement,
use SCM5B35.
–V
+V
Isolated
Computer-Side
Power
LPF
V
OUT
20
19
22
I/O Common
RD EN\
Linearizer
Power
Oscillator
+5V
17
16 Power Common
Isochopper™
Amplifier
Pat Pending
FEATURES
● INTERFACES TO 100Ω PLATINUM, 10Ω COPPER,
OR 120Ω NICKEL RTDs
● LINEARIZES RTD SIGNAL
● HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
●
ANSI/IEEE C37.90.1-1989
TRANSIENT PROTECTION
● INPUT PROTECTED TO 240VAC CONTINUOUS
● 160dB CMR
● 95dB NMR AT 60Hz, 90dB AT 50Hz
● CSA CERTIFIED, FM APPROVED, CE COMPLIANT
● MIX AND MATCH SCM5B TYPES ON BACKPANEL
DESCRIPTION
Each SCM5B34 RTD input module provides a single channel of RTD input
which is filtered, isolated, amplified, linearized, and converted to a high
level analog voltage output (Figure 1). This voltage output is logic switch
controlled, which allows these modules to share a common analog bus
without the requirement of external multiplexers.
DATAFORTH
A Burr-Brown Company
®
51 Call 800-444-7644
For Information and Assistance
SCM5B
Module SCM5B34
Input Range Limits –200°C to +850°C (100Ω Pt)
–80°C to 320°C (120Ω Ni)
–100°C to 260°C (10Ω Cu)
Input Resistance
Normal 50MΩ
Power Off 40kΩ
Overload 40kΩ
Input Protection
Continuous 240Vrms max
Transient ANSI/IEEE C37.90.1-1989
Sensor Excitation Current
100Ω Pt, 120Ω Ni 0.25mA
10Ω Cu 1.0mA
Lead Resistance Effect
100Ω Pt, 120Ω Ni ±0.02°C/Ω(1)
10Ω Cu ±0.2°C/Ω(1)
CMV, Input to Output
Continuous 1500Vrms max
Transient ANSI/IEEE C37.90.1-1989
CMR (50 or 60Hz) 160dB
NMR 95dB at 60Hz, 90dB at 50Hz
Accuracy See Ordering Information
Conformity Error ±0.05% Span
Stability
Input Offset ±0.01°C/°C
Output Offset ±20µV/°C
Gain ±35ppm of reading/°C
Noise
Input, 0.1 to 10Hz 0.2µVrms
Output, 100kHz 200µVrms
Bandwidth, –3dB 4Hz
Response Time, 90% Span 0.2s
Output Range 0V to +5V
Output Resistance 50Ω
Output Protection Continuous Short to Ground
Output Selection Time 6µs at Cload = 0 to 2000pF
(to ±1mV of VOUT)
Output Current Limit +8mA
Output Enable Control
Max Logic “0” +0.8V
Min Logic “1” +2.4V
Max Logic “1” +36V
Input Current, “0,1” 0.5µA
Power Supply Voltage +5VDC ±5%
Power Supply Current 30mA
Power Supply Sensitivity
100Ω Pt, 120Ω Ni 0.2°C/V
10Ω Cu 0.5°C/V
Mechanical Dimensions 2.28" x 2.26" x 0.60" (58mm x 57mm x 15mm)
Environmental
Operating Temperature Range –40°C to +85°C
Storage Temperature Range –40°C to +85°C
Relative Humidity 0 to 95% noncondensing
Emissions EN50081-1, ISM Group 1,
Class A (Radiated, Conducted)
Immunity EN50082-1, ISM Group 1,
Class A (ESD, RF, EFT)
SPECIFICATIONS Typical at TA= +25°C and +5V Power.
MODEL INPUT RANGE OUTPUT RANGE ACCURACY†
100Ω Pt **
SCM5B34-01 –100°C to +100°C 0V to +5V ±0.32°C
(–148°F to +212°F)
SCM5B34-02 0°C to +100°C 0V to +5V ±0.13°C
(+32°F to 212°F)
SCM5B34-03 0°C to +200°C 0V to +5V ±0.26°C
(+32°F to 392°F)
SCM5B34-04 0°C to +600°C 0V to +5V ±0.78°C
(+32°F to 1112°F)
10Ω Cu **
SCM5B34C-01
0°C to +120°C (10Ω at 0°C)
0V to +5V ±0.23°C
(+32°F to +248°F)
SCM5B34C-02
0°C to +120°C (10Ω at 25°C)
0V to +5V ±0.23°C
(+32°F to +248°F)
SCM5B34C-03
0°C to +160°C (10Ω at 0°C)
0V to +5V ±0.32°C
(+32°F to +320°F)
120Ω Ni **
SCM5B34N-01 0°C to +300°C 0V to +5V ±0.40°C
(+32°F to +572°F)
ORDERING INFORMATION
NOTES: (1) "Ω" refers to the resistance in one lead. †Includes conformity, hysteresis and repeatability.
**RTD STANDARDS
TYPE ALPHA COEFFICIENT DIN JIS
100Ω Pt 0.00385 DIN 43760 JIS C 1604-1989
120Ω Ni 0.00672
10Ω CU 0.004274
