Live readouts are different from collected data.

This information pertains to the original LabQuest.
If you have LabQuest 2, see LabQuest 2 FAQs and Troubleshooting

When used in Logger Pro, there is an issue in the LabQuest DAQ (data acquisition) firmware whereby live readouts and autoID functions interfere. The symptom is a discrepancy between live readout values, and what is seen after starting data collection.

The effect varies by sensor and is very noticeable with a pH sensor. Live readouts will show a noisy value that is from several tenths to several pH units high. Once data collection starts, the values will be consistent from reading-to-reading, but they will be different from the live readout value. The recorded values are the correct values.

This problem has been fixed in LabQuest App version 1.1 and newer, which is available as a free download at:
http://www.vernier.com/labquest/updates/