There are two common reasons for data loss:

  1. Relaunching a logger before the data has been saved
  2. Technical problem with the logger itself

The following section discusses data loss and its causes; it also discusses methods of retrieving lost data and how to insure against data-loss problems.

Data overwritten by another file can sometimes be retrieved:

  • It may be possible for Onset to reconstruct an overwritten or corrupted data file for you. We can recover the data in those instances where you have clicked "Start" and then stopped the logger soon after it started logging new data. Data cannot be recovered if the logger is started and allowed to log through an entire new deployment, because the previous data will be erased. The best case for recovering old data is if it has not been overwritten. However, if the majority of your previous data file is still stored in EEPROM, we can in most cases create a new header for the data file and restore the data that has not been overwritten.
  • To restore a partially overwritten data file,we need the exact start date and time of the overwritten file and the end time of the data file, if available Using this information, we can usually open the logger's file, cut out the new header and data points, and save the previous data by adding a new header. This data is only as accurate as the information provided to us. For example, if you estimate a launch time of 11:00 AM (with an actual launch time of 10:50 AM), your data will be shifted by 10 minutes.

Data that is missing, damaged, or has become irretrievable:

  • Complete data loss does sometimes occur due to logger failure or user error. To obtain the best results from our technical support team, explain clearly and with as much detail as possible the circumstances surrounding your data loss.
  • Our loggers store data in EEPROM, which retains its memory even if the logger stops, loses power, or has its battery removed. If there is no data on the chip, or the data has become corrupted, we will work with you to prevent the error from happening again.
  • Onset can sometimes retrieve data from loggers whose headers are scrambled. This is usually less successful because the header information is what enables the logger to record data in the first place. If the header is scrambled at launch time, in most cases the logger will not record data properly; but if the header was scrambled at readout or during deployment, data may be recoverable.

Correcting a data file's time information is also possible. This condition usually occurs when the host computer's clock is set incorrectly, causing a logger to be launched with an incorrect time. Products without EEPROM risk data loss if the battery fails or is removed: The Optic StowAway Shuttle (part number DTA128B) stores data on RAM; therefore data stored on the Optic Shuttle will be lost if the battery fails.

The Palm® handheld running HandCar® software does not store data in EEPROM. This product loses data if power is lost. Users of Palm® handheld connected organizers should read the product manual concerning battery life and battery replacement procedures.

What types of data reconstruction can a user accomplish? If you have a H8 family multi-channel logger and you accidentally select the wrong sensor during launch, the H08 File Converter can change the input device listed in your datafile to another one.

If you have additional questions regarding data loss or retrieval, contact Onset for technical support at If you decide to send your logger in for data retrieval, please note that charges will be incurred.


Tech Note