Impulse SCM7B37 - Manual

Isolated Process Control Signal Conditioning Products SCM7B
For information call 800-444-7644 78
SCM7B37
Isolated Thermocouple Input Modules
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.
Figure 1: SCM7B37 Block Diagram
▲
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 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 Approved
• CE and ATEX Compliant
Refer to AN701 for V
out
to
temperature conversion information