The Turner Designs C-sense pCO2 sensor is available in three ranges:
2400-001: 0-1000 ppm
2400-002: 0-2000 ppm
2400-003: 0-4000 ppm
To interface the C-sense to a NexSens iSIC or SDL500 data logger, the 0-5 VDC output is scaled to 0-2.5 VDC with a voltage divider. This needs to be taken into account when determining the scaling factors from the C-sense calibration certificate. The certificate includes a calibration equation in the form of y=mx+b, where y is the concentration of CO2 in ppm and x is the voltage output from the C-sense. An example calibration certificate for a C-sense with 0-4000 ppm range is shown in Figure 1.
To determine the scaling factors for use when adding a C-sense device in iChart:
1. Identify the calibration equation on the provided certificate. The 0 mV and 2500 mV (min and max ranges of the iSIC/SDL500) values must be determined.
2. For the 0 mV value, enter x=0 into the equation and determine y. For the 2500 mV value, enter x=5.0 into the equation and determine y. The x value is entered as 5.0 (and NOT 2.5) because the voltage divider used to scale the output to 0-2.5 VDC is external to the C-sense.
In the example calibration certificate shown in Figure 1, the calculated scaling factors are as follows:
0 mV = -42.403 ppm (806.85*0 – 42.403)
2500 mV = 3991.847 ppm (806.85*5.0 – 42.403)
3. When adding the device in the iChart Setup Device Wizard, enter the calculated scaling factors as shown in Figure 2. Also be sure to enable switch power (SW.A) by clicking the Show Detail button and entering the Duration.