CN-0357

Circuit Note

Rev. 0 | Page 4 of 5

Setup

Connect the electrochemical sensor to the socket on the EVAL-

CN0357-PMDZ circuit evaluation board.

Connect the EVAL-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