Scale WebSocket Bridge
Weighing indicators, on a websocket
Puts a terminal's weighing indicator on a websocket, so a web application can show a live weight without anything installed in the browser.
Five protocols, one message format
Each indicator frames its readings differently; a page receives the same JSON whichever scale is on the bench.
Configured by the server
Model, units, low and high limits arrive with the SCADA server's configuration, so changing a scale is a change on the server.
Says whether to trust the reading
Stability, under, over and off-scale are carried through from the indicator rather than inferred from numbers that will not settle.
Silence is a reading too
A scale that stops sending is reported offline after three seconds, because a page that simply stops updating cannot tell an empty platform from an unplugged cable.
Refuses to guess
An unrecognised model stops with the list of the ones it knows. A scale decoded with the wrong protocol reports plausible nonsense, which is worse than reporting nothing.
A weighing indicator streams its readings over a serial port in a format of its manufacturer’s choosing, and a web page cannot read either the port or the format. This does both: each reading arrives as a websocket message carrying the weight, its units and whether it can be trusted, so the page that shows a weight is an ordinary web page with no plugin, no driver and nothing to install on the terminal.
Which scale a terminal has, what units it works in and the limits a load must fall within are the SCADA server’s business, not the terminal’s. They arrive with the server’s configuration, so a scale is changed on the server and the terminal follows — no file to edit on site, and no terminal left reading a scale it no longer has.