Measurement Modes
Three measurement modes are present on the F-950: continuous, trigger and fixed volume. To change measurement mode go to Setup > Mode from the main menu (page 25).
In fixed volume and trigger mode, the instrument reports values in terms of VOC (volatile organic compounds). VOC’s are aromatic compounds like ethylene, esters and alcohols. Their production increase with produce aging and spoilage. The F-950 ethylene sensor cannot distinguish ethylene from many other VOC’s. PolarCept was designed to optimize and improve the accuracy of ethylene measurements. PolarCept is an external water filter, which reduces the signal from interfering gases reaching the ethylene sensor. PolarCept is recommended in Fixed Volume and Trigger mode. PolarCept dramatically reduces the amount of interfering gases like alcohols and esters that are present in a sample, allowing ethylene to pass through to the sensors. For more information on PolarCept, see page 11.
Continuous measurement mode measures the air entering through the input of the instrument. The controls default to Loop “Open” and Pump “On”. Continuous mode can be used with or without the sample port attached to the front of the instrument. The data is saved every one second in continuous mode.
Trigger measurement mode begins with the valve closed and the pump off. To start taking a measurement, press the square start button on the key-strip of the F-950 to initiate a new measurement. The pump will run and air will enter the F-950 until a stable reading has been reached for all sensors, or until the user stops the measurement by pressing the start button again. The final values will be displayed under the word “last” in the graph and saved to the SD card. The pump will then turn off until the user initiates a new measurement.
Trigger mode can be used with or without the sample port attached to the front of the instrument. The instrument will detect and report total VOC’s present in the sample.
Trigger mode should be used in place of continuous mode if expecting high ethylene concentrations. Trigger mode allows a purge of the internal volume of gas in the instrument between samples and will help protect the ethylene sensor from over-saturation.
Fixed Volume measurement mode draws in a sample of a small, set volume of gas (default 15 mL). The sampling port with the needle attachment is required for Fixed Volume mode and MAP applications. The instrument will detect and report total VOC’s present in the fixed volume sample.