CN0337 provides robust and complete solution for Temperature to digital conversion with isolation, for measurements where, standard RTD sensors are used. The design solution is optimized for high precision and low cost measurement, using only three active devices, and has a total unadjusted temperature error of less than 0.039%FSR/°C. The accuracy depends on the calibration. The circuit shown in Figure 1 incorporates AD8608ARZ OpAmp, AD7091RBRMZ 12-bit successive approximation (SAR) ADC, and ADuM5401ARWZ isolator to create a standard Temperature measurement system. The circuit has 12 pin PMOD connector on board, which could be used for connection to a customer microprocessor or FPGA. This CN0337 circuit note discusses the design steps needed to optimize the circuit shown in Figure 1 for a specific temperature range including component selection considerations.

The performance of the circuit could be demonstrated with the use of Analog Devices SDP controller EVAL-SDP-CB1Z and SDP-to-PMOD Interposer Board SDP-PMD-IB1Z, both optional purchase items. This user guide will discuss how to use the evaluation software to collect data from the EVAL-CN0337-PMDZ Evaluation Board CN0337

Figure 1. Resistance Deviation to Digital Conversion with Isolation Using Pt100 RTD Sensor (All Connections and Decoupling Not Shown)

• EVAL-SDP-CB1Z Controller Board (SDP-B Board)
• EVAL-CN0337-PMDZ Evaluation Board (CN-0337 Board)
• EVAL-CFTL-6V-PWRZ (+6V Power Supply) or equivalent
• SDP-PMD-IB1Z SDP-to-PMOD interposer board
• Resistance Decade (to simulate the input resistance of the RTD element), e.g. IET RS-200 Labs Resistance Substituter Decade Box. (If no calibration procedure is performed, the temperature can be measured using real sensor)
• CN0337 Evaluation Software
  • (supplied with provided CD in kit)
• 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

• The EVAL-CFTL-6V-PWRZ (+6V DC Power Supply) powers the EVAL-CN0337-PMDZ (CN0337 Board) via the DC barrel jack.
• The SDP-PMD-IB1Z (Interposer Board) connects to the EVAL-SDP-CB1Z (SDP-B Board) via the 120-Pin connector A.
• The EVAL-SDP-CB1Z (SDP-B Board) connects to the PC via the USB cable.
• The EVAL-CN0337-SDPZ (CN0337) connects to the EVAL-PMD-IB1Z (Interposer board) via the 12-Pin header PMOD connector (J1 and J3)
• The (Pt/100 Resistance Decade ) connects to the EVAL-CN0337-SDPZ (CN0337 Board) via the terminal block J2

1. Load the evaluation software by placing the CN0337 evaluation software disc in the CD drive of the PC. You can also download the most up to date copy of the evaluation software from www.analog.com/CN0337. Open the file setup.exe.
   
   

   NOTE: It is recommended that you install the CN0337 Evaluation Software to the default directory path C:/Program Files/Analog Devices/CN0337/ 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 CN0337 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.

   
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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:/C:/Program Files/Analog Devices/SDP/DriversR2

   
   
   

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

1. Connect the +6V DC Power Supply (Wallwart) to the barrel jack J1 of the Interposer Board (Interposer Board ) as depicted below.
   
   

   NOTE: Make sure that the jumper is positioned as shown below!

   
   
   
   
   
   
   
   
   

2. Connect the 120-pin connector on the SDP-PMD-IB1Z (Interposer Board) to the 120-pin connector marked “CON A” on the EVAL-SDP-CB1Z (SDP-B Board)
   
   
   
   
3. Connect the USB cable supplied with EVAL-SDP-CB1Z (SDP-B Board) to the USB port on the PC and the SDP Board
   
   
   
   

   NOTE: Verify that the SDP Drivers are loaded properly. For that purpose open the Device manager and check if the SDP Board is recognized. If not repeat steps 1-3

   
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4. Connect the EVAL-CN0337-PMDZ (CN0337 Board) to the SDP-PMD-IB1Z (Interposer Board) via the 12 pin header PMOD connector.
   
   
   
   
5. Connect the input current source (Current calibrator) to J2 Terminal Block. The polarity is shown on the picture below
   
   
   

1. Connect/Reconnect Button
   • When this button is pressed, the SDP-B Board makes a USB connection to the CN0337 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 CN0337 Board
4. Clear Data Button
   • When this button is pressed, the software will clear all data collected from the chart history.
5. Save Data Button
   • When this button is pressed, the software will save the data collected to a tab delimited ASCII spreadsheet file.
6. Control Tabs
   • Acquire DataMain - Clicking this tab brings the data collection graph to the front.
   • Calibrate System - Clicking this tab brings the system calibration settings to the front.
   • SDP Revision - Clicking this tab brings the SDP board information window to the front.
7. Numerical Indicator
   • This indicator displays the current reading value. The value units depend on the chosen graph units (10).
8. Graph
   • This graph displays the collected data. The units on the graph depend on the chosen graph units (10).
9. Graph Controls
   • These controls allow the user to zoon in, zoom out, and pan through the data collected.
10. Graph Units Radio Buttons
    • This control determines the units of the data displayed in the chart and the numerical indicator.
11. System Status String Indicator
    • This indicator displays a message to the user detailing the current state of the software.
12. System Status LED Indicator
    • This indicator displays the current state of the software in the form of an LED. There are four status LED colors.
      Inactive
      Busy
      Error
      Waiting for user action
      
13. Calibrate System Controls
    • These controls allow the user to calibrate the CN0337 Board. For the calibration procedure two input resistance values are required. For best performance the inputs have to be selected “100Ω” and “212Ω” . To perform the calibration follow the instructions on the screen.
      
      

      NOTE: If other temperature ranges or sensor are used the user has to look at the sensor’s reference table to choose the resistance calibration values!

      
      
      
      
      
      
      

14. SDP Firmware Revision
    • Read only data. After the connection is established with the SDP Board, the basic information for the controller can be found here.

1. Follow the instructions to properly install the software and connect the hardware as described in the previous sections.
2. Open the file named CN0337.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/CN0337/CN0337.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 Calibrate System tab.
3. Apply first calibration current to the input connector J2 of CN0337.
4. Write down the applied current to Calibration Resistance 1 indicator.
5. Press Calibrate 1 button.
6. Apply second calibration resistance to the input connector J2 of CN0337 and different from the previous calibration resistance.
7. Write down the applied resistance to Calibration Resistance 2 indicator.
8. Press Calibrate 2 button.

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. Capture Data.
3. Click the Save Data Button.
   
   
   
   
4. Click the OK Button.
5. Browse to the directory location where the spreadsheet file is to be saved.
6. Name the file.
7. Click the OK Button.
8. Open with Notepad or similar. The saved data shows the ADC Codes (decimal)