120
Call 800-444-7644
For Information and Assistance
DATAFORTH
A Burr-Brown Company
®
SCM7B37
Isolated Thermocouple Input Modules
FEATURES
● INTERFACES TO TYPE J, K, T, E, R, S, AND B THERMOCOUPLES
● PROVIDES HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
● ACCURACY, ±0.03% OF SPAN TYPICAL, ±0.1% MAX
● ANSI/IEEE C37.90.1-1989 TRANSIENT PROTECTION
● INPUT PROTECTED TO 120Vrms CONTINUOUS
● NOISE, 500µV PEAK (5MHz), 250µV RMS (100KHz)
● CMRR, 160dB
● NMR, UP TO 85dB
● EASY DIN RAIL MOUNTING
● CSA CERTIFIED, FM APPROVAL PENDING
● CE COMPLIANT
DESCRIPTION
SCM7B37 modules accept a single channel of input from Type J, K, T, E, R,
S, or B thermocouples. The signal is filtered, isolated, amplified, and
converted to a high level analog voltage for output to the process control
system (Figure 1).
Cold junction compensation (CJC) is performed using an NTC thermistor
(see “Additional SCM7B Part Numbers” section for P/N and AN701 for
further information) externally mounted under the field-side terminal block
on the backpanel (Figure 1). Open thermocouple detection is upscale using
a 30nA current source in the input circuitry.
These modules incorporate a five-pole filtering approach to maximize both
time and frequency response by taking advantage of both Thomson (Bessel)
and Butterworth characteristics. One pole of the filter is on the field side of the
isolation barrier; four are on the process control system side.
After the initial field-side filtering, the input signal is chopped by a proprietary
chopper circuit and transferred across the transformer isolation barrier,
suppressing transmission of common mode spikes and surges. The signal
is then reconstructed and filtered for process control system output.
Modules accept a wide 14 - 35VDC power supply range (+24VDC nominal).
Their compact packages (2.13"x1.705"x0.605" max) save space and are ideal
for high channel density applications. They are designed for easy DIN rail
mounting using any of the “-DIN” backpanels.
Fig 1: SCM7B37 Block Diagram
Refer to AN701 for Vout to
temperature conversion information
Surge
Suppression,
Protection,
LPF (1 pole),
Open Detection
and CJC
Backpanel
Term Block
–V
+V
*R
T
is a backpanel mounted NTC thermistor
used as a cold junction compensation (CJC)
sense element.
**Shield ground-tie shown for ungrounded
thermocouple configuration.
R
T
*
V
S
LPF
(4 pole)
Iso-Chopper II™
Amplifier
Pat Pending V
OUT
4
5
3
COM
(14-35V dc)
0
2
1
Shield**
Thermocouple
+
–
X
dc Supply
Field-Side
dc Supply/
Oscillator
Process Control
System-Side
1500V
Isolation Barrier
DATAFORTH
A Burr-Brown Company
®
121 Call 800-444-7644
For Information and Assistance
Module SCM7B37
Input
Signal Range Thermocouple1
(See Ordering Information below)
Bias Current -30nA
Resistance
Normal 50MΩ
Power Off 30kΩ min
Overload 30kΩ min
Protection
Continous 120Vrms max
Transient ANSI/IEEE C37.90.1-1989
Output
Signal Range2◆
Effective Available Power240mW
Resistance <1Ω
Protection Continuous Short-to-Ground
Voltage/Current Limit ±12V, ±14mA
CMV (Input-to-Output)
Continuous 1500Vrms
Transient ANSI/IEEE C37.90.1-1989
CMRR (50 or 60Hz) 160dB
Accuracy3±0.03% Span typical, ±0.1% Span max
Nonlinearity4See Ordering Information
Stability (-40C to +85°C)
Gain ±35ppm/°C
Input Offset ±0.5µV/°C
Zero Suppression ±0.005%(Vz)5/°C
Output Offset ±0.002% Span/°C
Noise
Peak @ 5MHz B/W 500µV
RMS @ 10Hz to 100kHz B/W 250µV
Peak @ 0.1Hz to 10Hz B/W 1µV
CJC Accuracy6, +5°C to +45°C ambient ±0.25˚C typ, ±1°C max
Open Input Response Upscale
Open Input Detection Time 10s max
Frequency and Time Response
Bandwidth, -3dB 3Hz
NMR (50/60Hz) 80/85dB
Step Response, 90% Span 150ms
Supply Voltage 14 to 35VDC
Current212mA
Sensitivity ±0.0001%/%VS
Mechanical Dimensions (H)(W)(D) 2.13" x 1.705" x 0.605" max
54.1mm x 43.3mm x 15.4mm max
Environmental
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -40°C to +85°C
Relative Humidity 0 to 90% noncondensing
Emmissions EN50081-1, ISM Group 1, Class A (Radiated, Conducted)
Immunity EN50082-1, ISM Group 1, Class A (ESD, RF, EFT)
MODEL ** INPUT RANGE ACCURACY (TYP)3ACCURACY (MAX)3NONLINEARITY (TYP)4NONLINEARITY (MAX)4
SCM7B37J-01 -100°C to +760°C (-148°F to +1400°F) ±0.03% (0.26˚C) ±0.1% (0.86˚C) ±0.1% (0.09˚C) ±0.02% (0.17˚C)
SCM7B37J-10 0°C to +200°C (+32°F to +392°F) " (0.06˚C) " (0.20˚C) " (0.02˚C) " (0.04˚C)
SCM7B37J-11 0°C to +400°C (+32°F to +752°F) " (0.12˚C) " (0.40˚C) " (0.04˚C) " (0.08˚C)
SCM7B37J-12 0°C to +600°C (+32°F to +1112°F) " (0.18˚C) " (0.60˚C) " (0.06˚C) " (0.12˚C)
SCM7B37J-13 +300°C to +600°C (+572°F to +1112°F) " (0.09˚C) " (0.30˚C) " (0.03˚C) " (0.24˚C)
SCM7B37K-02 -100°C to +1350°C (-148°F to +2462°F) " (0.44˚C) " (1.45˚C) " (0.15˚C) " (0.29˚C)
SCM7B37K-20 0°C to +300°C (+32°F to +572°F) " (0.09˚C) " (0.30˚C) " (0.03˚C) " (0.06˚C)
SCM7B37K-21 0°C to +600°C (+32°F to +1112°F) " (0.18˚C) " (0.60˚C) " (0.06˚C) " (0.12˚C)
SCM7B37K-22 0°C to +1200°C (+32°F to +2192°F) " (0.36˚C) " (1.20˚C) " (0.12˚C) " (0.24˚C)
SCM7B37K-23 +600°C to +1200°C (+1112°F to +2192°F) " (0.18˚C) " (0.60˚C) " (0.06˚C) " (0.12˚C)
SCM7B37T-03 -100°C to +400°C (-148°F to +752°F) " (0.15˚C) " (0.50˚C) " (0.05˚C) " (0.10˚C)
SCM7B37E-04 0°C to +900°C (+32°F to +1652°F) " (0.27˚C) " (0.90˚C) " (0.09˚C) " (0.18˚C)
SCM7B37R-05 0°C to +1750°C (+32F to +3182°F) " (0.53˚C) " (1.75˚C) " (0.18˚C) " (0.35˚C)
SCM7B37S-06 0°C to +1750°C (+32F to +3182°F) " (0.53˚C) " (1.75˚C) " (0.18˚C) " (0.35˚C)
SCM7B37B-07 0°C to +1800°C (+32F to +3272°F) " (0.54˚C) " (1.80˚C) " (0.18˚C) " (0.36˚C)
SPECIFICATIONS Typical at 25°C and +24VDC
NOTES
1 Thermocouple characteristics per NIST monograph 175, ITS-90.
2 Output Range and Supply Current specifications are based on
minimum output load resistance. Minimum output load resistance
is calculated by VOUT2/PE, where PE is the output Effective Available
Power that guarantees output range, accuracy, and linearity
specifications.
3 Accuracy includes the effects of repeatability, hysteresis, and
linearity.
4 Nonlinearity is calculated using the best-fit straight line method.
5 VZ is the nominal input voltage that results in a 0V output.
6 The CJC sensor accuracy should be added to the module accuracy
and thermocouple accuracy to compute the overall measurement
accuracy.
ORDERING INFORMATION
SCM7B
◆OUTPUT RANGES AVAILABLE
OUTPUT RANGE PART NUMBER MODIFIER EXAMPLE
+1 to +5V (none) SCM7B37J-01
0 to +5V A SCM7B37J-01A
0 to +10V D SCM7B37J-01D
**THERMOCOUPLE ALLOY COMBINATIONS
Standards: DIN IEC 584, ANSI MC96-1-82, JIS C 1602-1981
TYPE MATERIAL
J Iron vs. Copper-Nickel
K Nickel-Chromium vs. Nickel-Aluminum
T Copper vs. Copper-Nickel
E Nickel-Chromium vs. Copper-Nickel
R Platinum-13% Rhodium vs. Platinum
S Platinum-10% Rhodium vs. Platinum
B Platinum-30% Rhodium vs. Platinum-6% Rhodium
N Nickel-14.2% Chromium-1.4% Silicon vs. Nickel-4.4%
Silicon- 0.1% Magnesium
