Frequently Asked Questions – Web HMI

How do I show different images from multiple states?
Create 5 tags of the Data Type Boolean and set the Data Source to Calculation. Then in the calculation field you would add the logic to convert the integer value to a Boolean state. For example, if you wanted to set a Calculation to True when an integer tag equals 3, it would look like this:
[SomeIntegerTag.Value] = 3
Then after setting up the 5 Boolean tags you set them up in a group in the oas-tag-src attribute of the image tag in HTML:
<div id='test' oas-tag-src='{
    "type": "group",
    "all_f": "DefaultImageUrl",
    "bad_q": "BadDataQualityUrl",
    "group": [
            "tag": "SomeTag01.Value",
            "config": "SomeImageUrl01"
            "tag": "SomeTag02.Value",
            "config": "SomeImageUrl02"
            "tag": "SomeTag03.Value",
            "config": "SomeImageUrl03"
            "tag": "SomeTag04.Value",
            "config": "SomeImageUrl04"
            "tag": "SomeTag05.Value",
            "config": "SomeImageUrl05"
As long as the 5 states are mutually exclusive and only one can be true at a time, your image will switch to the associated image in the group section of the attribute. If none are true, it will default to the all_f URL, and if any tag in the group has bad data quality, the image will switch to the URLin the bad_q section.
For more information on Calculation Tags and how to use them, see the following:
How quickly can I update Web HMI screen elements?
We have customers updating over 100 elements on screen every second, but to get such rapid sub-second updates is not always realistic in a web browser. Network requests can take 50-500ms (or more) even on local networks, depending on the networking hardware and configuration. Then the web browser needs to process the incoming data and update elements based on your own javascript or the Web HMI markup rules. There are too many variables so any performance metrics are impossible to supply. We suggest experimentation within your own web application code and networking environment to determine your performance benchmarks.
Does Web HMI support SSL?
Using SSL with Web HMI is fully supported. You must first install an SSL Certificate on your server for the domain name(s) that you intend to use, for example “”. Once the certificate is installed properly on the server, check Use SSL and select the installed certificate from the dropdown menu. Purchasing and installing an SSL certificate is outside of the scope of the OAS product. For more information on Windows and Certificates, see the following article.
What is a good HTML editor other than Notepad?
You can use any editor you are familiar.  Notepad++ has a lot of options for representing HTML elements as well as editor functions and's also nice and clean:  
When there is a large number of Tags specified on one page I do not receive any data.
Use the max_tags_per_msg config parameter as shown in the Programming Reference-HTML5 – Other Configuration Options.
The format of numeric values is showing commas or decimal points and not following the regional language settings.
Use the locale config parameter as shown in the Programming Reference-HTML5 – Other Configuration Options.
What is the client side script to read or write a value?
Use the OPC.get_value(string) or OPC.set_value(string, string) functions as described in Programming Reference-HTML5 – Client Script Library Reference.