CN-0216 is a precision weigh scale signal conditioning system. It uses the AD7791, a low power buffered 24-bit sigma-delta ADC along with two external ADA4528-1 zero-drift amplifiers. This solution allows for high dc gain with a single supply.

Ultralow noise, low offset voltage, and low drift amplifiers are used at the front end for amplification of the low-level signal from the load cell. The circuit yields 15.3 bit noise-free code resolution for a load cell with a full-scale output of 10 mV.

This circuit allows great flexibility in designing a custom low-level signal conditioning front end that gives the user the ability to easily optimize the overall transfer function of the combined sensor-amplifier-converter circuit. The AD7791 maintains good performance over the complete output data range, from 9.5 Hz to 120 Hz, which allows it to be used in weigh scale applications that operate at various low speeds.

This user guide will discuss how to use the evaluation software to collect data from the EVAL-CN0216-SDPZ Evaluation Board (CN-0216 Board)

• EVAL-SDP-CB1Z Controller Board (SDP-B Board)
• EVAL-CN0216-SDPZ Evaluation Board (CN-0216 Board)
• EVAL-CFTL-6V-PWRZ (+6V Power Supply) or equivalent
• CN0216 Evaluation Software

• PC with the following Minimum Requirements
  • Windows XP Service Pack 2 (32-bit)
  • USB type A Port
  • Processor rated at 1GHz or faster
  • 512 MB RAM and 500 MB available hard disk space
• USB type A to USB type mini-B cable
• Tedeah Huntleigh Model 1042 Load Cell

• The EVAL-CN0216-SDPZ (CN-0216 Board) connects to the EVAL-SDP-CB1Z (SDP-B Board) via the 120-Pin connector
• The EVAL-CFTL-6V-PWRZ (+6V DC Power Supply) powers the EVAL-CN0216-SDPZ (CN-0216 Board) via the DC barrel jack
• The EVAL-SDP-CB1Z (SDP-B Board) connects to the PC via the USB cable.
• The Tedeah Huntleigh Model 1042 load cell connects to the EVAL-CN0216-SDPZ (CN-0216 Board) via the 8 pin header.
  
  

1. Extract the file CN0216 Eval Software.zip and open the file setup.exe.
   
   

   NOTE: It is recommended that you install the CN0216 Evaluation Software to the default directory path C:/Program Files/Analog Devices/CN0216/ and all National Instruments products to C:/Program Files/National Instruments/

   

2. Click Next to view the installation review page
   
   
   
   
3. Click Next to start the installation
   
   
   
   
4. Upon completion of the installation of the CN0216 Evaluation Software, the installer for the ADI SDP Drivers will execute.
   
   

   NOTE: It is recommended that you close all other applications before clicking “Next”. This will make it possible to update relevant system files without having to reboot your computer.

   
   
   
   
   

5. Press “Next” to set the installation location for the SDP Drivers.
   
   

   It is recommended that you install the drivers to the default directory path
   C:/Program Files/Analog Devices/SDP/Drivers

   
   
   

6. Press “Next” to install the SDP Drivers and complete the installation of all software. Click “Finish” when done.
   
   

1. Connect the Tedeah-Huntleigh (Model 1042) Load Cell to 8-pin header of the EVAL-CN0216-SDPZ (CN-0216 Board) as depicted below.
   
   

   NOTE: If a different Load Cell is used other than the
   Tedeah-Huntleigh Model 1042, the wiring schematic will be different!

   
   
   
   
   
   
   

1. Connect/Reconnect Button
   • When this button is pressed, the SDP-B Board makes a USB connection to the CN-0216 Board. A connection to the SDP-B Board must be made to use the software.
2. Run Button
   • When this button is pressed, the SDP-B Board will collect conversion data and present the acquisitions in the chart.
3. Stop Button
   • When this button is pressed, the software stop collecting data from the CN-0216 Board
4. Clear Chart Button
   • When this button is pressed, the software will clear all data collected from the chart history.
5. Control Tabs
   • Main - Clicking this tab brings the data collection chart to the front.
   • Calibrate System - Clicking this tab bring the system configuration settings to the front.
6. Current Weight Numerical Indicator
   • This indicator displays the mass (in grams) on the load cell.
7. Chart Controls
   • These controls allow the user to zoom-in, zoom-out, and pan through the data collected.
8. Select Units Radio Buttons
   • This control determines the Y-Axis units of the data displayed in the chart.
9. System Status String Indicator
   • This indicator displays a message to the user detailing the current state of the software.
10. System Status LED Indicator
    • This indicator displays the current state of the software in the form of an LED. There are three status LED colors.
      Inactive
      Busy
      Error
      
11. Calibration Weight Numerical Control
    • Set this control to the weight of the object used to calibrate the load cell.
12. Calibrate Button
    • Pressing this button initiates the calibration of the load cell.
13. ADC Mode Radio Buttons
    • This control is used to set the mode of the AD7791. The default value is Unbuffered Mode and is highlighted in bold on the Calibrate System Tab.
      • Buffered Mode - Selecting this mode turns the on-chip analog input channel buffer of the AD7791 ON.
      • Unbuffered Mode - Selecting this radio button turns the on-chip analog input channel buffer of the AD7791 OFF.
14. ADC Channel Select Radio Buttons
    • This control is used to select the analog input channel of the AD7791 for conversion. The default value is AIN(+)-AIN(-) and is highlighted in bold on the Calibrate System Tab.
      • AIN(+)-AIN(-) - Selecting this radio button allows for normal operation of the AD7791.
      • AIN(-)-AIN(-) - Selecting this radio button shorts the analog input channels of the AD7791.
      • Vdd Monitor - Selecting this radio button monitors the voltage applied to the Vdd pin of the AD7791. The voltage is attenuated by 5 and the resultant voltage is applied to the ∑-Δ modulator using an internal 1.17 V reference for analog to digital conversion.
15. Update Rate Radio Buttons
    • This control is used to change the output word rate of the AD7791. The default value is 9.5 Hz and is highlighted in bold on the Calibrate System Tab.
16. Configure ADC Button
    • When this button is pressed the current value of the ADC Mode Radio Buttons, ADC Channel Select Radio Buttons, and Update Rate Radio Buttons are used to configure the AD7791.

1. Follow the instructions to properly install the software and connect the hardware as described in the previous sections.
2. Open the file named CN0216.exe in the installation directory.
   
   

   NOTE: If the software was installed to the default location it will be found at
   C:/Program Files/Analog Devices/CN0216/CN0216.exe

   
   
   
   
   
   
   

3. Click the Connect/Reconnect Button. A window with a progress bar will load.
   
   
   
   
4. Upon success, the System Status String Indicator will display SDP Board Ready to Acquire Data

1. Establish a USB Connection Link.
2. Click the Run Button
3. Click the Stop Button when acquisition is complete.

1. Establish a USB Connection Link.
2. Click the Calibrate System Control Tab.
3. Set the Calibration Weight Numerical Control to the weight (in grams) of the weight to be used for calibration.
4. Place the calibration weight on the Load Cell.
5. Click the Calibrate Button and Wait for calibration to complete.
   
   
   
   
6. Remove the calibration weight when prompted to do so.
   
   
   
   
7. Click the Continue Button.
8. Wait for calibration to complete.