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Strain Gage Measurement Using SC-2043-SG with DAQPad-1200

Hardware: Legacy DAQ Devices>>Multifunction DAQ>>DAQPad-1200

Problem: How do I use the SC-2043-SG with the DAQPad-1200 for strain gage measurements? What are the general guidelines for strain gage measurements with the SC-2043-SG and any DAQ device?

Solution:
Important Notes:
  • When using DAQPads or DAQCards, you must provide an external power supply of +5 Volts (connected to connector J8 on SAC-2043-SG). Also, set SW1 to external, and the green LED on the 2043 should light up.

  • The DAQ device must be in Non-referenced Single Ended mode.

  • SC-2043-SG only requires analog input channels 0 to 7 (singled-ended) on your DAQ device. All the other channels of the DAQ device are available at the screw terminal on 2043. You can use the 2043 as a connector block to access signals directly from the DAQ device. For more information, refer to the Signal Connections chapter in the SC-2043-SG User Manual.



    • Setting up your system for strain gage measurement
    1. Connect the DAQ-Pad 1200 with your parallel (printer) port. From the front side of the DAQPad-1200, take an NB1 (50-pin cable) and connect it to J9, the connector closer to the DC-DC converter. Note that this connector is used for Lab/1200 Series devices while connector J10 is used for MIO devices.

    2. Provide external +5V power to power your SC-2043-SG. With DAQPads and DAQCards, you must provide a separate power supply (+5V), which is connected to terminal J8 (located on top, left of the DC-DC converter). Also, set SW1 switch to external position. Note that the green LED lights up when you supply the power. If the LED does not light up, then your SC-2043-SG is not receiving any power.

    3. Set the following jumpers for a half-bridge strain gage measurement:

      • SW1 should be set to external.

      • The SC-2043-SG provides an internal excitation voltage up to 2.5 V. If you need higher excitation voltage, then you should connect an external power supply—up to 10V—to connector J7. Also, set jumper W1 and W3 to internal or external, depending on the source of your excitation.
      • MIO devices:You can measure the excitation voltage supplied by the SC-2043-SG by routing it through itself to the DAQ device. To do this, set the jumper W2 to EX position to route the excitation through channel 0. You can then use only channels 1 to 7 for strain gage measurement. If you want to use CH0, you should put W2 in CH0 position. You can also put jumper W8 in EX position to route the excitation through analog CH8 and put W2 in CH0 to use all channels 0 to 7 for strain gage measurement. If you do not want to measure excitation voltage at all, you can put W8 in ST position and W2 in CH0 position and use channels 0 to 7 for strain gage measurement.
        Lab/1200 devices: Set W2 in EX position to route the excitation voltage supplied by the SC-2043-SG back to the SC-2043-SG through channel 0. You can then use only channels 1 to 7 for strain gage measurement. Set W2 to CH0 to use all channels 0 to 7 for strain gage measurement. In this case, you cannot measure the excitation voltage supplied by the SC-2043-SG. Jumper W8 should always be in ST position.

      • You can use any combination of full, half, or quarter bridge strain gages with the SC-2043-SG. You must set the jumper for the appropriate channel in half or full bridge position. For quarter bridge, you also must manually add resistor in the sockets provided. Refer to chapter 2 in the manual.

    4. Launch the NI-DAQ configuration utility and test the device. Remember, you must configure the SC-2032-SG as an accessory. The configuration wizard also prompts you to select whether the voltage is routed to CH0 or CH8 or not routed at all.

    5. To test the device, you can route the excitation voltage to CH0 by setting appropriate jumpers as discussed in step 3 above. From the NI-DAQ test panels, you can measure CH0 on the DAQPad-1200. You should read 2.5 V, the internal excitation voltage provided by the SC-2043-SG.
    6. Connect your strain gage to CH1. Make sure you wire connections to excitation and channel inputs correctly. Normally, the red wire connects to EX+, black to EX-, and white connects to CH1+. If you have a ground wire, you can connect it to the AIGND pin of the device (available on the screw terminals of the SC-2043-SG). With the DAQPad-1200, connect the ground to pin 11.

    7. Measure CH1 from the NI-DAQ test panels. The strain gage determines the voltage values, typically a few hundred microvolts to millivolts. Deflect the strain gage in both directions (compression and tension) and notice the voltage value going from –ve to +ve.

    8. Open the micro-strain gage example in LabVIEW from LabVIEW\Examples\DAQ\Solutions\transduc.llb. Set the excitation voltage and Rg value and measure channel 1. This should provide the strain gage directly.



    Related Links: Product Manuals: SC-2043-SG User Manual

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    Report Date: 11/18/1998
    Last Updated: 03/24/2006
    Document ID: 1FH7PHX4

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