CN-0357 Circuit Note
Rev. 0 | Page 4 of 5
Setup
Connect the electrochemical sensor to the socket on the EVA L-
CN0357-PMDZ circuit evaluation board.
Connect the EVA L-CN0357-PMDZ to the interposer board and
ensure that the jumper on the interposer board selects +3.3 V as
the configuration. Next, connect the SDP-B board to the
interposer board and apply power to the interposer board via
the DC barrel jack.
Connect the USB cable supplied with the SDP-B board to the
USB port on the PC and to the SDP-B board.
The software can communicate with the SDP board if the
Analog Devices System Development Platform driver appears
in the Device Manager. When USB communications are
established, the SDP board can now send, receive, and capture
serial data from the EVAL-CN0357-PMDZ circuit evaluation
board.
Test
Navigate to the installation location of the CN-0357 Evaluation
Software and open the CN0357.exe file. (The file should be located
in a folder named Analog Devices in the start menu of the
operating system.)
When the application opens, the software automatically connects to
the SDP-B board. If multiple SDP-B controller boards are
connected, the selected board will have a light emitting diode
(LED) blinking.
The CN-0357 Evaluation Software User Guide contains
information and details regarding how to use the evaluation
software for data capture.
The input signal for this board is gas concentration; therefore, a
calibration gas source is required. When testing with carbon
monoxide, consider that 250 ppm is the maximum short term
exposure limit.
The software is designed to be used with any electrochemical
sensor, so it is important to input the correct specifications for the
chosen sensor.
The maximum sensor sensitivity and sensor range are needed to
calculate and set the resistance of the AD5270-20 digital rheostat.
This value is a signed value. Positive values are used to describe
sensors than sink current, whereas negative values are used to
describe sensors that source current.
The typical sensor sensitivity is used to calculate the system
conversion coefficient of ppm/mV.
Pressing the Run button begins acquisition of concentration data at
1 second intervals.
Figure 4 shows the circuit response after rapidly removing the
sensor from the 175 ppm CO atmosphere and is a better
representation of circuit performance.
A photo of the EVAL-CN0357-PMDZ board is shown in
Figure 5.
Figure 4. Response to a 175 ppm to 0 ppm Step of Carbon Monoxide
Figure 5. EVAL-CN0357-PMDZ Evaluation Board
