Windmill Software Ltd
Windows Engineering Software

July 2006

Logging only New Data

Logging Only New Data from Scientific Instruments and Data Acquisition Devices

The Windmill Logger program regularly saves data from sensors and instruments to the computer's hard disk. You can choose to log continuously, or to only record a value when new data arrives. The latter allows external events to control logging.

The data does not have to change to be logged. For example, imagine you are using our COMIML serial driver to gather data from an electronic balance. Every time you press a button on the balance, COMIML takes a reading. It might be that two consecutive readings happen to be identical. However, every time COMIML takes a reading it updates a "record number". Logger watches the record number and so knows when new data is available, even if it is the same value as the previous reading.

To set Logger up to log only new data:

Open Logger and make sure that the first channel of data to be logged is the one to be monitored for updates. For data supplied by COMIML, this should be the channel holding the record number.
Select Settings from the menu bar.
Tick "Log on First Channel Change".
Enter a logging duration of 0 and press OK.
Press the Start button.

Using Logger with the COMIML Serial Driver

COMIML acquires data from instruments connected to your PC by RS232, RS422, RS485 or Modbus. Logger can then grab the data from COMIML and save it to file.

To log only new data you need to allocate the final channel in COMIML to store the record number.

To do this...

In comDebug (the COMIML configuration program) go to the Terminal screen
Press the Parse button. The Reply Parser window appears. It should show a number of channels, each configured to extract an item of data (temperature, pressure, latitude, etc.)
Select the first blank action cell.
From the Extract menu select Extract Record Number.
Add a new channel, click it and confirm you want to select it.

Logging with Excel

Instead of using the Windmill Logger program, you could use Excel to record data. For instructions on logging with Excel see http://www.windmill.co.uk/excel.html. For how to use Excel to log only new data see Issues 56 and 57 of the Monitor newsletter.

Windmill Software Ltd Windows Engineering Software

Logging only New Data

Logging Only New Data from Scientific Instruments and Data Acquisition Devices

Using Logger with the COMIML Serial Driver

Logging with Excel

Further Reading

Windmill Software Ltd
Windows Engineering Software