114
Call 800-444-7644
For Information and Assistance
DATAFORTH
A Burr-Brown Company
®
SCM7B34/34N
Isolated Linearized 2- Or 3-Wire RTD Input Modules
FEATURES
● INTERFACES TO 100Ω PLATINUM OR 120Ω NICKEL RTDS
● PROVIDES 250µA RTD EXCITATION CURRENT
● LINEARIZES RTD SIGNAL RESPONSE
● PROVIDES HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
● ACCURACY, ±0.05% TO ±0.15% OF SPAN TYPICAL
● NONCONFORMITY, ±0.025% TO ±0.07% OF SPAN TYPICAL
● ANSI/IEEE C37.90.1-1989 TRANSIENT PROTECTION
● INPUT PROTECTED TO 120Vrms CONTINUOUS
● NOISE, 500µV PEAK (5MHz), 250µV RMS (100KHz)
● CMRR, UP TO 160dB
● NMR, UP TO 85dB
● EASY DIN RAIL MOUNTING
● CSA CERTIFIED, FM APPROVAL PENDING
● CE COMPLIANT
DESCRIPTION
Each SCM7B34/34N RTD input module accepts a single channel of 100Ω
Platinum (α = 0.00385) or 120Ω Nickel (α = 0.00672) RTD input and
produces an input voltage in response to a low level current excitation. The
input signal is filtered, isolated, amplified, linearized, and converted to a high
level analog voltage for output to the process control system (Figure 1).
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.
In response to the low level current excitation signal, the RTD 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.
Linearization is achieved by creating a non-linear transfer function through
the module itself. This non-linear transfer function is configured at the factory
and is designed to be equal and opposite to the specific RTD non-linearity.
Lead compensation is achieved by matching two current paths thus cancelling
the effects of lead resistance.
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: SCM7B34/34N Block Diagram
Linearization
Surge Suppression,
Protection, Lead
Compensation, LPF
(1 pole), and RTD
Current Stimulus
Backpanel
Term Block
–V
+V
RTD
Shield*
NOTE: For 2-wire operation, jumper the
(–) and (x) connections on the
backpanel term block.
* Shield ground-tie shown for ungrounded
RTD sensor configuration.
LPF
(4 pole)
Iso-Chopper II™
Amplifier
Pat Pending
0
2
1
V
S
V
OUT
4
5
3
COM
(14-35V dc)
+
–
X
dc Supply
Field-Side
dc Supply/
Oscillator
Process Control
System-Side
1500V
Isolation Barrier
DATAFORTH
A Burr-Brown Company
®
115 Call 800-444-7644
For Information and Assistance
ORDERING INFORMATION
MODEL INPUT RANGE ACCURACY2NONCONFORMITY3
TYPICAL MAX TYPICAL MAX
100Ω Pt **
SCM7B34-01 -100°C to +100°C (-148°F to +212°F) ±0.075% (0.15˚C) ±0.15% (0.30˚C) ±0.025% (0.05˚C) ±0.05% (0.10˚C)
SCM7B34-02 0°C to +100°C (+32°F to +212°F) ±0.10% (0.10˚C) ±0.2% (0.20˚C) ±0.025% (0.025˚C) ±0.05% (0.05˚C)
SCM7B34-03 0°C to +200°C (+32°F to +392°F) ±0.075% (0.15˚C) ±0.15% (0.30˚C) ±0.025% (0.05˚C) ±0.05% (0.10˚C)
SCM7B34-04 0°C to +600°C (+32°F to +1112°F) ±0.05% (0.30˚C) ±0.1% (0.60˚C) ±0.025% (0.15˚C) ±0.05% (0.30˚C)
SCM7B34-05 -50°C to +350°C (-58°F to +662°F) ±0.05% (0.20˚C) ±0.1% (0.40˚C) ±0.025% (0.1˚C) ±0.05% (0.20˚C)
120Ω Ni **
SCM7B34N-01 0°C to +300°C (+32°F to +572°F) ±0.15% (0.45˚C) ±0.3% (0.90˚C) ±0.06% (0.18˚C) ±0.12% (0.36˚C)
SCM7B34N-02 0°C to +200°C (+32°F to +392°F) ±0.15% (0.30˚C) ±0.3% (0.60˚C) ±0.07% (0.14˚C) ±0.14% (0.28˚C)
Module SCM7B34 SCM7B34N
Input
Signal Range 100Ω Pt RTD 120Ω Ni RTD
(See Ordering Information below) *
Protection
Continous 120Vrms max *
Transient ANSI/IEEE C37.90.1-1989 *
Output
Signal Range1◆◆
Effective Available Power140mW *
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 *
Accuracy2(See Ordering Information below) *
Nonconformity3(See Ordering Information below) *
Stability (-40C to +85°C)
Gain ±60ppm/°C*
Input Offset ±1µV/°C*
Zero Suppression ±0.002%(RZ/RSPAN)4/°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*
Lead Resistance Effect ±0.02°C/Ω max *
Sensor Excitation Current5≈250µA*
Frequency and Time Response
Bandwidth, -3dB 3Hz *
NMR (50/60Hz) 80/85dB *
Step Response, 90% Span 250ms *
Supply Voltage 14 to 35VDC *
Current112mA *
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) *
SPECIFICATIONS Typical at 25°C and +24VDC
◆OUTPUT RANGES AVAILABLE
OUTPUT RANGE PART NUMBER MODIFIER EXAMPLE
+1 to +5V (none) SCM7B34-01
0 to +5V A SCM7B34-01A
0 to +10V D SCM7B34-01D
NOTES
*Specification same as preceding model.
1 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 conformity specifications.
2 Accuracy includes the effects of repeatability, hysteresis, and conformity.
3 Nonconformity is calculated using the best-fit straight line method.
4RZ is the value of the RTD resistance at the lowest measurement point. RSPAN is
the change in resistance over the measurement span.
5Sensor excitation current is model dependent.
SCM7B
**RTD STANDARDS
TYPE ALPHA COEFFICIENT DIN JIS
100Ω Pt 0.00385 DIN 43760 JIS C 1604-1989
120Ω Ni 0.00672
