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Using SC-204X Boards with M Series DAQ Devices

Hardware: Multifunction DAQ (MIO)>>M Series, Signal Conditioning Other>>SC Analog Accessories>>SC-2040, Signal Conditioning Other>>SC Analog Accessories>>SC-2043-SG, Signal Conditioning Other>>SC Analog Accessories>>SC-2042-RTD

Problem: Can I use the SC-204X boards with M Series DAQ boards?

Solution: Yes, the SC-2040, SC-2042RTD, and SC-2043SG boards can be used with M Series DAQ devices and chosen as an accessory in Measurement and Automation Explorer. The input channels of the DAQ device should be set to differential mode and can be directly connected to the SC-204X boards using the SHC-68-68-EPM cable.

There are 3 SC-204X boards: SC-2040, SC-2042RTD, and SC-2043SG. SC-2040 is an eight-channel simultaneously sampling differential amplifier for DAQ boards. SC-2042-RTD is an eight-channel signal conditioning board that interfaces RTD signals to DAQ boards. The SC-2043-SG is an eight-channel signal conditioning board that interfaces strain gauge signals to DAQ boards.

SC-2040:
The SC-2040 is only supported through version 8.0.1 of the DAQmx driver. In subsequent versions of the DAQmx driver, this device cannot be selected as an accessory, and thus cannot be used. For DAQmx 8.0.1 and prior, the SC-2040 requires extra steps to make it work correctly as an accessory because NI-DAQmx does not route the necessary sample and hold signal to PFI7 that the SC-2040 requires. To work around this, follow these steps:
  • Export the AI Sample Clock to PFI7 so that the SC-2040 goes in and out of sample and hold mode at the correct times. Use the VI DAQmx Export Signal or the function DAQmxSetExportedSampClkOutputTerm and choose PFI7 as the output terminal.


  • As the SC-2040 requires that the signal on PFI7 stay high while the analog to digital conversions on each channel take place, you must change the properties of the sample clock from "pulse" to "level". To do this, use the property SampClk.OutputBehavior in the DAQmx Export Signal property node in LabVIEW. In C, set DAQmxSetExportedSampClkOutputBehavior to DAQmx_Val_Lvl.


  • There are requirements for the hold time for different accuracies listed in the specifications section of the manual for the SC-2040 (linked below). After determining the hold time that you need to use, you will need to set the delay between the first edge of the sample clock and the time that the first sample is actually acquired. To do this, use the property DelayFromSampClk.Delay in the DAQmx Timing property node or the C function DAQmxSetDelayFromSampClkDelay.


  • There are requirements for the tracking time also listed in the manual that need to be met. To ensure that these are met, you may need to adjust the rate of your convert clock. The convert clock governs the switching of the multiplexer (see KnowledgeBase 30LDURMV linked below for more information). To calculate the tracking time for a given convert clock period use the following equation:
    Track Time = Sample Clock Period - (Hold Time + (#Channels*Convert Clock Period))
    To change the convert clock rate, use the property AIConv.Rate in the property node DAQmx Timing or the C Function DAQmxSetAIConvRate.


  • The last consideration when using the SC-2040 with NI-DAQmx is that if you use the dip switches to specify a gain other than 1, the driver will not scale the data correctly. This can be easily fixed by dividing the data by whatever gain factor you have chosen.

SC-2042RTD and SC-2043SG:
The SC-2042RTD and SC-2043SG can both be used with NI-DAQmx. If you are using an RTD or Strain Gauge Task or Channel you must choose external excitation and set it to the values provided by these accessories. Also, the SC-2043SG provides a gain of 10 to the strain gauge signal that must be taken into account.

Related Links:
Product Manual: SC-2040 User Manual
Product Manual: SC-2042RTD User Manual
Product Manual: SC-2043SG User Manual
KnowledgeBase 30LDURMV: Difference Between the Scan Clock (Sample Clock) and the Channel Clock (Convert Clock)
KnowledgeBase 3ECDRBPK:Can I Use M Series Boards With ER-8/16 Relay Module?
KnowledgeBase 3FDC9SNK: Using SSR Modules with M Series DAQ Devices
KnowledgeBase 3FDD52NK: Using SC-206X Boards with M Series DAQ Devices
KnowledgeBase 143F47QH: Connecting the Correct SC-207X Breadboard to an SCXI-1180 Feedthrough Panel
KnowledgeBase 3FDDDJNK: Using BNC-208X Boards with M Series DAQ Devices

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Report Date: 11/14/2004
Last Updated: 04/20/2007
Document ID: 3FDCUMNK

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