Table of Contents
Complete Closed-Loop Precision Analog Microcontroller Thermocouple Measurement System with 4 mA to 20 mA Output (CN0300)
This circuit using the ADUCM360 shows how a thermocouple and RTD can be amplified and sampled using the internal Programmable Gain Amplifier and high performance ADC. The DAC output is then set to control the 4-20mA transmitter interface. CN0300 demonstrates the high performance and circuit integration of the ADUCM360 - Amplifier, ADC, CPU, DAC and OP-AMP all in one-chip!
- EVAL-CN0300-EB1Z Evaluation board.
- USB Cable
- One PC or Laptop
- T-Type Thermocouple
Minimum PC/System Requirements
- One PC with the following
- Windows XP SP2, Windows Vista or Windows 7 Business/Enterprise/Ultimate editions
- Intel Pentium processor (x86 compatible), 1GHz or faster
- 512 MB RAM and 1 GB available hard disk space
- USB port
How to Install the Evaluation Software
- Ensure your PC has the USB drivers for the USB-SWD/UART board.
- To Install the drivers for the USB-SWD/UART board, unzip the CDM 2.04.06~.zip file for Windows XP drivers
- For other operating systems, go to the FTDI website:
Step by Step Instruction for Connecting the Hardware
- Connect the EVAL-CN0300-EB1Z board to the USB-SWD/UART board.
- Connect the USB-SWD/UART board to your PC via a USB cable. (Ensure the driver is installed correctly)
Opening and Enabling the Evaluation Software
- You now need to determine what com port your PC has allocated to your USB-SWD/UART board
Calibrating the DAC (Only needed if a Recalibration is desired)
- Using the “Browse” tab, call the file CN0300_test.hex
- Next, force the part into download mode – to do this, hold the “SD” button on the EVAL-CN0300-EB1Z board while pressing and releasing the “RESET” button.
- Next close CM3WSD and open HyperTerminal on your PC.
- Set Hyperterminal for the appropriate COM port and for 9600 baud rate, 8 data bits, No parity, 1 stop bit, no flow control.
- Your current meter should report a value close to 4mA – if it doesn’t follow the instructions on the HyperTerminal screen to calibrate the DAC output to 4mA by pressing the “1” or “0” keys accordingly. Ensure you select the HyperTerminal screen before pressing 1 or 0.
- Press return when the current meter reports 4mA
- The Final temperature reported should be within a few degrees C of the expected ambient temperature. +/-5C is fine since the ADC is not fully calibrated.
- Close CM3WSD. Return to HyperTerminal and select “Connect” by pressing the phone icon.