Ethylene Sensor Span Calibration
The two ethylene sensors in the F-900 have different calibration schedules. The C₂H₄ PPB & PPM sensor requires weekly calibration and 3 month span calibration (typically a 5% drift per month; recalibration required more often if more accuracy is desired).
Before performing a span calibration:
First perform a zero calibration.
The F-900 driver must be downloaded and installed using the F-900 Package Setup v1.0.exe found on the webpage (http://felixinstruments.com/support/f-900-support/software), as well as detailed instructions. The F-900 Package Setup includes the F-900 Controller software necessary for the span calibration.
Set C₂H₄ PPB Span
Connect the F-900 to the PC using the USB cable. Power on the F-900 and open the F-900 Controller software (Latest version of Java required. Check http://www.java.com/)
- If the F-900 display becomes frozen consistently when connecting to the PC, it is possible the SD card is corrupted. To repair, insert the SD card in the computer. If the PC reports disk error, choose "scan and fix". If not right click on the SD card drive > Properties > Tools > Scan. Press and hold the power button for 10 seconds to force a shut-off if the F-900 freezes.
The device serial number should appear in the upper left corner of the F-900 Controller software and a message should appear indicating that the device is connected in USBHID mode. Click on the device serial number to connect to that specific instrument. The F-900 Controller software can have more than 1 device connected at a time.
On the F-900, navigate to Measure and press the right arrow to begin a measurement. Press the right arrow again to skip the sensor stabilization.
There is a short lag in the F-900 Controller software as it pulls data from the F-900 instrument. This lag interval is adjustable in 1 second intervals. The monitor view data should begin to appear and update in the F-900 Controller software, including ethylene, temperature, RH, flow rate, and CO₂ or O₂ if optional sensors are enabled.
Select the Calibration tab in the F-900 Controller software. Select the tab for F-900 to see the various calibrations possible (Zero individual sensors with N₂, Relative Humidity (RH), O₂ Span, CO₂ Span, C₂H₄ Span.)
See the last calibration listed: C₂H₄: Use C₂H₄ standard.
Select C₂H₄ PPB to calibrate the ppb sensor.
Enter the exact ethylene concentration from the calibration standard gas in ppb (ex: 1555 ppb) in the F-900 Controller software. Recommended calibration gas is 1.5 ppm ethylene, balanced with pure air.
Connect the 1.5 ppm ethylene standard gas to the F-900 intake. Verify that the F-900 measurement settings have Chamber In, Chamber Out and Closed Loop turned off.
If using an On Demand Flow Regulator, directly connect the regulator to the IN port on the F-900. When using an On Demand-Flow Regulator, the gas is drawn out of the regulator/cylinder by the pump of the F-900. When the regulator is fully twisted onto the cylinder, the PSI on the gauge will move. Rotate the regulator until it is tightly onto the cylinder of gas (clockwise).
The regulator can be removed from the cylinder (a small puff of gas will escape) to be used with other gas cylinders or for storage. To remove the regulator, twist counter-clockwise.
Figure 18: Ethylene calibration gas cylinder with On Demand Flow Regulator connected to F-900 IN port.
If not using an On Demand Flow Regulator, be sure to use a t-valve release extra pressure to avoid damaging the F-900. Alternatively, a flow meter can be connected to be sure that the flow going into the F-900 is appropriate levels and gas is not being wasted. Always open the regulator very slowly and allow only 1-2 PSI (6-13 kPa) until the ethylene value starts to increase on the F-900.
Watch the ethylene data on the F-900 Controller software now that the standard gas is connected. The data should be trending towards the expected concentration and begin to stabilize.
Wait at least 7 minutes once the signal has stabilized (and does not change more than 40 ppb) before setting the span calibration. To set the span calibration, verify the correct concentration is entered in ppb in the F-900 Controller software and click the set span button. Note the value below has stabilized at 1.311 ppm.
Once the set span button is pressed, the span concentration (ex: 1.555 ppm) should appear on the F-900 display as well as in the F-900 Controller software. The concentration level should remain at stable values after setting the span.
Disconnect the calibration gas and watch the data trend toward ambient ethylene levels.
