8B47K-05: 8B Linearized Thermocouple Input Modules

8B47K-05
8B Linearized Thermocouple Input Modules

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Description

8B modules are an optimal solution for monitoring real-world process signals and providing high-level signals to a data acquisition system. Each 8B47 module isolates, filters, amplifies, and linearizes a single channel of temperature input from a thermocouple and provides an analog voltage output.

Linearization is accomplished using a four breakpoint piecewise linear approximation.

The 8B47 can interface to industry standard thermocouple types J, K, and T and has an output signal of 0 to +5V. Each module is cold-junction compensated to correct for parasitic thermocouples formed by the thermocouple wire and screw terminals on the mounting backpanel. Upscale open thermocouple detect is provided by an internal pull-up resistor.

Signal filtering is accomplished with a 3-pole filter optimized for time and frequency response which provides 70dB of normal-mode rejection at 60Hz. One pole of this filter is on the field side of the isolation barrier for anti-aliasing, and the other two are on the system side.

A special input circuit on the 8B47 module provides protection against accidental connection of power-line voltages up to 240VAC. Clamp circuits on the I/O and power terminals protect against harmful transients.

The modules are designed for installation in Class I, Division 2 hazardous locations and have a high level of immunity to environmental noise.

Features

  • Interfaces to Types J, K, and T Thermocouples
  • Linearizes Thermocouple Signal
  • High-Level Voltage Outputs
  • 1500Vrms Isolation
  • ANSI/IEEE C37.90.1 Transient Protection
  • Input Protection to 240VAC Continuous
  • 120dB CMR
  • 70dB NMR at 60Hz
  • Low Drift with Ambient Temperature
  • Accurate CJC –40°C to +85°C
  • CE Compliant
  • C-UL-US Listed
  • ATEX Compliance Pending
  • Mix and Match Module Types on Backpanel

Block Diagram

FAQ

Frequently Asked Questions


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.

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.

Can I power multiple 8B backplanes off of a single power supply?
You can use a single 5V power supply to power multiple backplanes, but you need to be aware of the current rating of your power supply and the current draw of your 8B modules. The current rating of your power supply needs to be greater than the total current draw of all the modules in your system (ideally 1.5x the total current draw). You can check the current draw of various 8B modules by checking their datasheets.

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.

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.

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.

If a thermocouple is soldered to a lead that has current running through it, how do you avoid affecting the thermocouple signal and subsequent measurement?
The thermocouples must be isolated so current does not come from the circuit under test and run through them. SCM5B, SCM7B, 8B, DSCA, DSCT, MAQ20 all offer the required isolation.

Why do only a few 8B modules have a +/-5V output?
Some 8B modules (such as 8B34 and 8B47) cannot have bipolar output due to limitations in the internal linearization circuitry.

If I don’t have an 8BPWR-2, can I use a +5VDC power supply to power my 8B backplane?
Yes, you can. The 8BPWR-2 is not required to power the 8B backplanes, it is used in situations where you don't have a +5VDC power supply and need to regulate the voltage of whatever current power supply you are using down to +5VDC so that it can be used for the 8B backplane.

Please make sure when choosing your +5VDC power supply that the current rating of the supply is acceptable for the total current draw of your system.

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

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.

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.

Does the 8B series backplanes identify the module slots on the PWB via silkscreen or other methods? Does it also mark the terminal blocks +/- inputs?
The 8B backpanels identify the module slots and their associated terminal block with silkscreen text (this includes the +/- inputs). The text is descriptive and matches up with the diagrams in our datasheets.

What is the correct backpanel for my 8B38 module?
Any of the backpanels in the 8B series will work for the 8B38 module. In fact, any of the 8B modules can be mounted to any of the 8B backpanels.

Will a 32kV signal damage the 8B47?
The 8B47 is input protected up to 240VAC and can withstand common mode voltages up to 1500Vrms max. A 32kV signal would damage the module.

What voltage does the 8B47 output on an open input?
The 8B47 has an upscale open input response. Standard product 5V output modules will go to 8V for upscale. Standard product 10V output modules will go to 13V for upscale.

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.

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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