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
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
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.
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
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
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).
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