Monitor - ISSN 1472-0221
The Newsletter for Data Acquisition and Control
Issue 285 October 2022
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You can download Monitor as a pdf file from https://www.windmill.co.uk/monitor/monitor285.pdf.
Contents
* Extracting data from serial messages
* Your Data Acquisition Questions Answered: USB Connection Dropping?
Extracting data from serial messages
Web link: https://www.windmill.co.uk/parse.html
When you collect data from instruments that communicate over RS232, RS485, Modbus you need to extract the essential readings from the superfluous padding: parising the message to obtain just the data items in which you are interested.
Windmill offers free data collection software for serial instruments. You can download this for free for one instrument from https://www.windmill.co.uk/serial.html. Or, as a Monitor subscriber, you are entitled to the whole Windmill software suite for free, just email monitor@windmillsoft.com.
How to locate your data
Using Windmill you have three methods of locating your data item:
- Search for specific characters in the message string.
- Ignore characters until one of the ones you want appears.
- Ignore a number of characters in the message string.
At first glance methods one and two seem to do the same job, but there are differences.
- When you search for characters the next action occurs AFTER the search term. When you ignore characters the next action occurs ON the specified character. So if you searched for a + sign you would not be able to extract it, but if you ignored all characters until the + sign you would.
- A search will look for the entire string specified (eg "abc"), whilst ignoring characters will stop at any of the characters specified (eg "a" or "b" or "c")
More Information
For full details of collecting data, see https://www.windmill.co.uk/parse.html. Here we give examples of the types of data string you might receive from different instruments, and tips on data acquisition.
Your Data Acquisition Questions Answered: USB Connection Dropping?
Question
"I run a pilot plant with data logging. Every so often, I get a USB port error."
Answer
Usually this error is because Windows has got out of sync with the USB, and the problem is that the USB handlers have no means of recovery from error, short of unplugging the usb lead from the computer and plugging it back in. Windows 10 is susceptible to this. A cure is to swap you USB device for one communicating over Ethernet, which is more robust. One example of this is the Microlink 851. Any Windmill setup files, programs and connection box would remain the same.
For more information see https://www.windmillsoft.com/
