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Reading data files with *.wdd format from WebDAQ-504




I am doing measurements with WebDAQ-504 and the data files are stored in *.wdd files. I came across the following webpage and realized that the wdd files store the data in json format: https://kb.mccdaq.com/KnowledgebaseArticle50726.aspx

I tried reading the wdd file using the json module in python but I get the following error message related to encoding format: 'utf-8' codec can't decode byte 0xc5 in position 2: invalid continuation byte

I appreciate it if someone helps with reading the wdd file and convert them to json, numpy array, panda data-frame, or other well-known formats. 

P.S.: I have tried converting the data files to csv format. However, a limited number of samples can be converted each time, and for long measurements it needs to be repeated so many times. So, converting all samples to json is prefered.

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Hello @Sajad

Measurement Computing provides you with 2 options to convert WebDAQ data files (.wdd) to csv:


the link you provided (

21 hours ago, Sajad said:


offers you the option to create your own app.  Perhaps you didn’t quite understand the knowledgebase article?  The file is divided into three sections and only one of them is json format.  There is a fixed size binary header (not json), followed by a json header (the size of the json header can vary and is defined in the last 4 bytes of the binary header), followed by binary data until the end of the file.

Note that the Newtonsoft.Json nor built-in json package of Python, when used by itself will not work as it does not handle the other 2 sections of the .wdd file.

There is also a REST api that allows you to access the data as it is collected by the WebDAQ.  More information on this is located  https://www.mccdaq.com/downloads/WebDAQ/REST-API/1.0.0/



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