Frequently Asked Questions
How do the SCM7B22 and SCM7B41 differ?
The main difference is the SCM7B41 is an input module and the SCM7B22 is an output module.
This means that.
The 7B41 module has its input on the isolated field side of the module connect to it through screw terminal blocks. The 7B41 module has its output on the system and power supply side of the module connect to it through DB-25 connector (SCM7BP01, SCM7BP02, SCM7BP04, SCM7BP08, and SCM7BP16).
The 7B22 module has its output on the isolated field side of the module connect to it through screw terminal blocks.
The 7B22 module has its input on the system and power supply side of the module connect to it through DB-25 connector (SCM7BP01, SCM7BP02, SCM7BP04, SCM7BP08, and SCM7BP16).
Keywords/Phrases: 7B, 7B module, 7B input module, 7B output module, 7B22, 7B41
What is the function of backpanels for signals?
Think of the backpanel as a bidirectional signal transfer device whose direction is determined by the module in a particular channel.
For an input module, the signal is transferred from the field-side screw terminals to the system/power supply-side screw terminals or to a signal access ribbon cable header or D-sub connector.
For an output module it is just the reverse, the signal is transferred from the system/power supply-side screw terminals or from a signal access ribbon cable header or D-sub connector to the field-side screw terminals.
Keywords/Phrases: backpanel, 5B backpanel, 7B backpanel, 8B backpanel, SCMD backpanel
How do I verify module accuracy?
Long story short, they believe the modules may be less accurate than specified. The biggest error seems to be a low voltage (1-2V), with error decreasing as Vin approaches 10V.
The biggest error at low voltage with error decreasing as Vin approaches 10V means that they are calculating error as % of reading.
Accuracy of Dataforth modules is specified and calculated as % of Span. The method is the following.
Set the test voltage.
Apply it to the module input.
Measure the voltage at the module input.
Calculate the expected module output voltage using the measured input voltage.
Measure the output voltage.
Calculate the % of Span error by the following formula.
Accuracy error % Span = ((Measured Vout – Calculated Vout) / Output Span V ) x 100
This method works for input or output modules.
Keywords/Phrases: Module accuracy, accuracy %, accuracy % of Span, Dataforth method for calculating Span accuracy
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 firstname.lastname@example.org
SCM7B – why are there many bipolar input models, but a lot fewer bipolar output models offered?
The SCM7B series is defined for the process industry which has a preference for unipolar signals on the system / power supply side of the module. In fact , there is a preference for a positive offset above a zero current or voltage output, such as, 4-20mA rather than 0-20mA, 1-5V rather than 0-5V, and 2-10V rather than 0-10V.
Keywords/Phrases: SCM7B bipolar input / bipolar output, SCM7B bipolar output, bipolar output
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.
Is the optional plug-in conversion resistor required in order to use the SCM7B32 module?
No, the optional plug-in conversion resistor is not shipped with nor is it required in order to use the SCM7B32 module. The current/voltage conversion is achieved by an internal resistor as shown in the block diagram in the data sheet.
Keywords/Phrases: SCM7B32, internal resistors, plug-in conversion resistor
What is the total power consumption of the 7B backpanel?
The total power requirement on the DC power rail is the summation of the power requirement of the individual modules as specified in each module specification. For power budget purposes, multiply the total power requirement you calculated by 1.5 for maximum power needed.
Keywords/Phrases: 7B backpanel, power consumption, power requirement, total power, total power requirement
For SCM7B22 modules when I give LabVIEW (or other DAQ software) an output command, I get no output from the backpanel, why?
That’s because the SCM7B22 and the SCM7B39 are output modules, are connected the reverse of input modules, they have their inputs on the system side (power supply side) of the backpanel. They provide their output on the isolated field side of the backpanel.
Keywords/Phrases: 7B, 7B module, 7B output module, 7B22, 7B39
Can SCM7B22 drive +/-10V, 2.5mA input with 0-200Hz sine wave?
“I am generating a sine voltage signal with frequency range 0-200Hz, +/-10V using a national instruments module NI 9263 with current drive capability of 1mA. The power amplifier I am driving the sine wave generated with has an input impedance of 4K ohms .(so for a 10V sine wave input to the amplifier, it will send 2.5mA to drive it).
I am trying to double check if the SCM7B22 would be suitable for my application since it has output current capability of +/-20mA.”
It was confirmed that the SCM7B22 would be suitable for his application. I also asked him to keep in mind the 7B22 has a 400Hz bandwidth and the filter is already attenuating slightly at 200Hz. At 200Hz, the output amplitude will be about 91.4% of the input amplitude (about 8.6% attenuated).
On the 8B51, can I apply the + and – input leads “backwards” to reverse the polarity of the output signal?
This can be done only if the voltage source is floating (isolated); this pertains also to the SCM7B modules.
Better modules for true differential operation for which a floating source is not needed are the DSCA30/31/40/41. Other modules for this type of operation are the SCM5B30/31/40/41 used with an SCMPB07-x with the I/O COM jumpers Jn removed in the channels for which true differential operation is desired. Both the DSCA and the SCM5B outputs can float +/-50V with respect to power supply common.
Keywords/Phrases: 8B51, reverse input leads, true differential
Do SCM7BP02 and SCM7BP04 have CJC sensors installed by default?
All SCM7B backpanels, including SCM7BP02 and SCM7BP04 have CJC sensors installed by default in every field input terminal in every channel. There is no separate model number for including CJC sensors as in SCM5B and 8B backpanels.
KEYWORDS/PHRASES: SCM7B backpanels, CJC sensors
Is the calibration of Dataforth modules traceable to NIST standards?
Yes, calibration of Dataforth modules is traceable to NIST standards.
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.
Does Dataforth have any options for thermistor input?
Thermistor interface has never been designed for SCM7B, 8B, DSCT, or MAQ20 product lines. However, we do have some custom products in the SCM5B line that can accept thermistor interface. Any SCM5B36, SCM7B36, 8B36, DSCA36, DSCT36 module with potentiometer input 0-10kohm may also be suitable for some sensors.
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
Is the SCM7B32-01 a suitable replacement for the Analog Devices 7B32-01-1?
Yes, the SCM7B32-01 is a direct replacement for the 7B32-01-1. Any application that uses a 7B32-01-1 will support an SCM7B32-01, and vice versa.
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.
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.
Is it possible to utilize remote CJC with the 7B47 modules?
SCM7B47 modules are designed to interface the 100k NTC thermistors which are installed on the SCM7B backpanels. Therefore, remote CJC is only possible if the 100k thermistor is replaced with a fixed resistor which requires a custom backpanel.
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.
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