DATAFORTH
A Burr-Brown Company
®
60
Call 800-444-7644
For Information and Assistance
SCM5B38
Strain Gage Input Modules, Wide Bandwidth
FEATURES
● INTERFACES TO 100Ω THRU 10kΩ,FULL-BRIDGE, HALF-BRIDGE,
OR QUARTER-BRIDGE STRAIN GAGES
● HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
●
ANSI/IEEE C37.90.1-1989
TRANSIENT PROTECTION
● INPUT PROTECTED TO 240VAC CONTINUOUS
● FULLY ISOLATED EXCITATION SUPPLY
● 100dB CMR
● 10kHz SIGNAL BANDWIDTH
● ± 0.08% ACCURACY
● ± 0.02% LINEARITY
● ± 1µV/°C DRIFT
● CSA CERTIFIED, FM APPROVED, CE COMPLIANT
● MIX AND MATCH SCM5B TYPES ON BACKPANEL
DESCRIPTION
Each SCM5B38 Strain Gage input module provides a single channel of
Strain Gage input which is filtered, isolated, amplified, 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.
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.
The SCM5B38 can interface to full-bridge or half-bridge transducers with
a nominal resistance of 100Ω to 10kΩ. A matched pair of bridge-
completion resistors (to ±1mV at +10V excitation) allows use of low cost
half-bridge or quarter-bridge transducers (Figures 2, 3, 4). The 10kHz
bandwidth allows measurement of high speed processes such as vibration
analysis.
Strain Gage excitation is provided from the module by a very stable 10V
or 3.333V source. The excitation supply is fully isolated, allowing the
amplifier inputs to operate over the full range of the excitation voltage. This
feature offers significant flexibility in real world applications. Full scale
sensitivities of 2mV/V, 3mV/V or 10mV/V are offered as standard. With 10V
excitation, this results in ±20mV, ±30mV or ±100mV full scale input range
producing ± 5V full scale output.
The input signal is processed through a pre-amplifier on the field side of
the isolation barrier. This pre-amplifier has a gain-bandwidth product of
5MHz and is bandwidth limited to 10kHz. After amplification, the input
signal is chopped by a proprietary chopper circuit. Isolation is provided by
transformer coupling, again using a proprietary technique to suppress
transmission of common mode spikes or surges. The module is powered
from +5VDC, ±5%.
Special input circuits on the SCM5B38 module provide protection of the
signal inputs and the isolated excitation supply up to 240VAC.
FIGURE 1. SCM5B38 Block Diagram.
–V
LPF
+In
–In
–EXC
Backpanel
Term Block
6
5
3
Surge
Suppression
and
Protection +V
Isolated
Field-Side
Power
Power
Oscillator
Isolated
Computer-Side
Power
V
OUT
20
19
22
I/O Common
RD EN\
+5V
17
16 Power
Common
4
3
2
1
+EXC
–V
+V
4
Isolated
Excitation
Source
1
2
Strain
Gage Isochopper™
Amplifier
Pat Pending
LPF
DATAFORTH
A Burr-Brown Company
®
61 Call 800-444-7644
For Information and Assistance
Full Bridge Half Bridge
Module SCM5B38-01, -02, -05, -06, -07 SCM5B38-03, -04
Input Range ±10mV to ±100mV
*
Input Bias Current ±0.3nA *
Input Resistance
Normal 50MΩ*
Power Off 40kΩ*
Overload 40kΩ*
Signal Input Protection
Continuous 240Vrms max *
Transient ANSI/IEEE C37.90.1-1989 *
Excitation Output
(-02, -04, -05, -07)
+10V ±3mV *
Excitation Output
(-01, -03, -06)
+3.333V ±2mV *
Excitation Load Regulation ±5ppm/mA *
Excitation Stability ±15ppm/°C*
Half Bridge Voltage Level (-04) NA +5V ±1mV
Half Bridge Voltage Level (-03) NA +1.667V ±1mV
Isolated Excitation Protection
Continuous 240Vrms max *
Transient ANSI/IEEE C37.90.1-1989 *
CMV, Input to Output
Continuous 1500Vrms max *
Transient ANSI/IEEE C37.90.1-1989 *
CMR (50 or 60Hz) 100dB *
NMR (–3dB at 10kHz) 120dB per Decade above 10kHz *
Accuracy(2) ±0.08% Span ±10µV RTI(3) *
Nonlinearity ±0.02% Span *
Stability
Input Offset ±1µV/°C*
Output Offset ±40µV/°C*
Gain ±25ppm of Reading/°C*
Noise
Input, 0.1 to 10Hz 0.4µVrms 2µVrms
Output, 100kHz 10mVp-p *
Bandwidth, –3dB 10kHz *
Rise Time, 10 to 90% span 35µs*
Setting Time, to 0.1% 250µs*
Output Range ±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 170mA Full Exc. Load, 70mA No Exc. Load *
Power Supply Sensitivity ±2µV/% RTI(3) *
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) *
MODEL (10kHz) INPUT BRIDGE TYPE INPUT RANGE EXCITATION OUTPUT RANGE
SCM5B38-01 Full Bridge 100Ω to 10kΩ3.333V at 3mV/V Sensitivity –5V to +5V
SCM5B38-02 Full Bridge 300Ω to 10kΩ10.0V at 3mV/V Sensitivity –5V to +5V
SCM5B38-03 Half Bridge 100Ω to 10kΩ3.333V at 3mV/V Sensitivity –5V to +5V
SCM5B38-04 Half Bridge 300Ω to 10kΩ10.0V at 3mV/V Sensitivity –5V to +5V
SCM5B38-05 Full Bridge 300Ω to 10kΩ10.0V at 2mV/V Sensitivity –5V to +5V
SCM5B38-06 Full Bridge 100Ω to 10kΩ3.333V at 10mV/V Sensitivity –5V to +5V
SCM5B38-07 Full Bridge 300Ω to 10kΩ10.0V at 10mV/V Sensitivity –5V to +5V
SPECIFICATIONS Typical at TA = +25°C and +5V power. FIGURE 2. Full Bridge Connection.
ORDERING
INFORMATION
* Same as –01, –02, –05, –06, –07 modules.
NOTES: (1) Strain element. (2) Includes excitation error, nonlinearity,
hysteresis and repeatability. (3) Referenced to input.
FIGURE 4. Quarter Bridge Connection.
FIGURE 3. Half Bridge Connection.
4
6
5
3
+EXC
+In
–In
–EXC
R
g
(1)
Backpanel
Terminal Block
SCM5B38-03
SCM5B38-04
R
1
R
2
NC
R
1
= R
2
R
g
(1)
4
3
2
1
V
EXC
4
6
5
3
+EXC
+In
–In
–EXC
Rg(1)
Backpanel
Terminal Block
SCM5B38-03
SCM5B38-04
R
1
R
2
NC
R
1
= R
2
R3
Customer
Supplied
4
3
2
1
V
EXC
4
6
5
3
VEXC
+EXC
+In
–In
–EXC
R
g
(1)
R
g
(1)
R
g
(1)
R
g
(1)
Backpanel
Terminal Block
SCM5B38-01
SCM5B38-02
SCM5B38-05
SCM5B38-06
SCM5B38-07
4
3
2
1
SCM5B
