SCM7B34/34N: Isolated Linearized 2- Or 3-Wire RTD Input Modules. Dataforth

Specialists in data acquisition, signal conditioning and data communication

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Each SCM7B34/34N RTD input module accepts a single channel of 100 ohm Platinum (a = 0.00385) or 120 ohm Nickel (a = 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.

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.

Interfaces to 100 Ohm Platinum or 120 Ohm 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 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 Approved
CE and ATEX Compliant

Isolated Linearized 2- Or 3-Wire RTD Input Modules

SCM7B34/34N Devices

Part Number	Input Configuration	RTD Type	Input Range	Output Range	Mechanical Format
SCM7B34-01 Order Now	2 & 3 Wire	100 Ohm Platinum	-100 to 100 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34-01A Order Now	2 & 3 Wire	100 Ohm Platinum	-100 to 100 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34-01D Order Now	2 & 3 Wire	100 Ohm Platinum	-100 to 100 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34-02 Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 100 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34-02A Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 100 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34-02D Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 100 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34-03 Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 200 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34-03A Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 200 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34-03D Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 200 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34-04 Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 600 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34-04A Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 600 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34-04D Order Now	2 & 3 Wire	100 Ohm Platinum	0 to 600 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34-05 Order Now	2 & 3 Wire	100 Ohm Platinum	-50 to 350 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34-05A Order Now	2 & 3 Wire	100 Ohm Platinum	-50 to 350 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34-05D Order Now	2 & 3 Wire	100 Ohm Platinum	-50 to 350 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34N-01 Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 300 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34N-01A Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 300 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34N-01D Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 300 (°C)	0 to +10 V	Modular plug-in-board
SCM7B34N-02 Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 200 (°C)	+1 to +5 V	Modular plug-in-board
SCM7B34N-02A Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 200 (°C)	0 to +5 V	Modular plug-in-board
SCM7B34N-02D Order Now	2 & 3 Wire	120 Ohm Nickel	0 to 200 (°C)	0 to +10 V	Modular plug-in-board

Frequently Asked Questions

Can Dataforth provide calibration reports for modules I purchased?

Yes we can provide calibration reports for the modules that you purchased.

You can either
a) visit https://www.dataforth.com/TestDataReport.aspx to search for Test Report Datasheets by Serial Number or
b) you can send us a list of model numbers and their serial numbers to support@dataforth.com

Is the calibration of Dataforth modules traceable to NIST standards?

Yes, calibration of Dataforth modules is traceable to NIST standards.

Analog Devices announced a last time buy and discontinuance of their signal conditioning modules. Can I replace them with Dataforth signal conditioning modules?

Yes, in general, Dataforth signal conditioning modules are a direct replacement for all Analog Devices signal conditioning modules. e.g. "SCM5B35-xx: Linearized 4-Wire RTD Input Modules" will replace Analog Devices "5B35: Isolated 4 Wire RTD Input Signal Conditioning Module".

Please note that Dataforth signal conditioning modules are RoHS II compliant.

If I purchase a backplane with no CJC, will I still be able to use modules that require the CJC enable jumper to be installed?

Yes. Backplanes with no CJC will still come with the CJC enable installed on the backplane.

If the input range of my signal conditioner is -1V to +1V and the output range is 0 to 10V, does this mean that it ignores polarity?

A signal conditioner with these I/O ranges does not mean that the module ignores the polarity of your voltage input. The output of voltage input modules are scaled linearly, meaning an input of -1V would correspond to an output of 0V, an input of 0V would correspond to an output of 5V, an input of +1V would correspond to an output of 10V, and so on.

How do I convert an RMS voltage to its corresponding peak voltage?

To convert an RMS voltage to its corresponding peak voltage, you simply take the RMS voltage value and multiply it by the square root of 2, or roughly 1.414.

For example, 1500Vrms corresponds to a peak voltage of 1500 * 1.414 = 2121 Vp

Where can I find the MTBF of my module?

Information on MTBF for SCM5B, SCM7B, 8B and DSCA is available on our website. Please see application note AN802 for more details. Application notes can be found under the "Literature" tab on the top navigation bar.

Can SCM5B modules be hot swapped?

Not just SCM5B modules, but any signal conditioning module series and MAQ20 I/O modules can be hot swapped. A minimal amount of signal settling time may result, but there will be no damage to the device.

What does "Response time, 90% span" mean on the datasheet for my module?

Normally, a response time figure refers to how quickly a module's output can "respond" to a change in the input signal. "Response time, 90% span" refers to how fast a module can adjust its output when a step signal is applied at the input, where the magnitude of this step input is 90% of the input span of the module.

Is the SCMXPRT-003 DIN rail mountable?

The SCMXPRT-001 has an option for DIN rail mounting (part number: SCMXPRT-001D) but the SCMXPRT-003 does not. Instead, it can be mounted on the SCMXRK-002 which is a 19 inch metal rack for mounting the SCMXPRT-003 as well as various Dataforth backpanels and the SCMXIF interface board.

How does the load resistance of a module affect the noise at the output?

Noise at the output of a module is independent of load resistance.

What does it mean when an input module has for example a 3kHz bandwidth?

A 3kHz bandwidth on an input module means it can accept voltages from DC to 3000Hz. Any frequency higher than that and the signal will start to be attenuated by the filter at the input.

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Model Number	Input Range	Output Range	Bandwidth	Sensor Type	Status*	Comments
SCM7B34-03-1621 Request Quote	0 to +200C	+1V TO +5V	3HZ	100 OHM PLATINUM RTD	PR	Same as SCM7B34-03 with 20mA output current
SCM7B34-1366 Request Quote	0 TO 150C	+1 TO +5V	3HZ	100 OHM PLATINUM RTD	QU	accuracy -/+0.15%max, -/+0.1% typical
SCM7B34-1374 Request Quote	0 TO 150C	+1 TO +5V	3HZ	100 OHM PLATINUM RTD	QU	same as 7B34-1366
SCM7B34-1416 Request Quote	-50C TO +150C	0V TO 10V	3Hz	2 - 3 WIRE RTD	QU
SCM7B34-1500 Request Quote	-100C TO +200C	0V TO 10V	10Hz	100 OHM PLATINUM RTD	QU
SCM7B34-1527 Request Quote	-51C TO +176C	0V TO 5V	3Hz	200 OHM PLATINUM RTD	PR
SCM7B34-1631 Request Quote	-300F TO +300F	+1V TO +5V	3Hz	100 OHM PLATINUM RTD	PR	Minimum output load 200 Ohm
SCM7B34-1649 Request Quote	-50C TO +350C	+1V TO +5V	3Hz	100 OHM PLATINUM RTD	PR	Minimum output load 200 Ohm
SCM7B34-1693 Request Quote	0C TO +200C	0V TO +10V	3HZ	50 OHM PLATINUM RTD	PR	Alpha = 0.00392
SCM7B34-1756 Request Quote	-200 TO +200C	0V TO +10V	3HZ	100 OHM PLATINUM RTD	PR
SCM7B34-1796 Request Quote	39 Ohm TO 104 Ohm	0V TO +10V	3HZ	RESISTANCE INPUT	PR	Output Voltage is linear with respect to Input Resistance
SCM7B34-1797 Request Quote	78 Ohm TO 208 Ohm	0V TO +10V	3HZ	RESISTANCE INPUT	PR	Output Voltage is linear with respect to Input Resistance