What are internal devices?

nipponbiki

Member
Join Date
Jun 2005
Posts
4
Hello everyone.

Sorry for the basic question. I am not a PLC tech, just a Japanese-English translator who has to translate some GOT manuals for Mitsubishi.

What are the internal devices of the GOT? Are they real hardware devices or just virtual devices? If virtual, are they simply for the purpose of mapping actual hardware devices on the PLC itself?

My understanding is that the GOT is simply a tool to monitor the PLC, so I can't understand why it would have any devices of its own.

Please help!
Say true and thankya.

Jason Daniels
ITP Technical Translator
 
Note:

After doing a little more searching on my own after posting, I am now wondering if the GOT is used for more than just monitoring. The reason I was thinking it was only used for monitoring the status of the PLC is because that's the wording used in the Japanese. Maybe the Japanese means more than just monitoring. Hard to say because its just the English word monitor put into their alphabet.

Anyway, thanks in advance for any input.

Jason
 
Apparently it's an HMI touchscreen. The HMI can be monatoring real switches, trasnducers, values in the plc etc.. It depends on how the HMI is setup for the project; the possabilities are endless. The devices you see on the touchscreen are virtual representations of the system status & components.
 
Well apart from "devices on screen visualisation", a term 'devices' in this case might refer to electronic components the panel is made of, also it might refer to hardware functions provided by panel so for example: i/o ports, memory (size), internal power supply unit, memory card interface, integrated real-time clock etc
OR maybe devices refers to different PLC vendors' drivers.

Hard to say without reading the whole sentence.
 
Yes, GOTs (graphical operation terminal) are Mitsubishi's HMIs.

The devices seem to be actual memory allocations for values from whatever is connected to the PLCs and math devices like SIN, TAN, etc. They can be bit devices, word devices, double-word, or 8-bit devices.

If you look at the file I attached, which is just a clip of a table in the manual, it seems the word device and its meaning is standardized for PLCs.

What exactly do you mean by virtual devices? Are there actual memory addresses used for these devices in the HMI's memory? Or, are they just mappings to the actual memory locations in the actual PLC? It seems to me that if actual memory addresses in the HMI are used, they are not anymore virtual than those on the PLC, right?


Thanks again,

Jason Daniels
ITP Technical Translator
 
nipponbiki said:
What exactly do you mean by virtual devices? Are there actual memory addresses used for these devices in the HMI's memory?

Let's say that the HMI is connected to a plc. The PLC might have some analog inputs that would be reading the level in a tank via an ultrasonic sensor. The sensor in the tank bounces sound waves off the material in the tank and reads the time it takes for the soundwaves to return to the sensor (kinda like radar), then converts that value into a voltage anywhere between 2 volts (for empty) & 12 volts (for full). The PLC converts that voltage into numbers and places thoes numbers in to an alocated memory location. That number might be anywhere between 0 (for empty) and 9999 (for full). The HMI would then poll the plc and read the spicific plc memory for level, and take that number and convert that information and display it as an analog guage drawn on the HMI screen in a "virtual" representation of an analog/mechanical guage with a sweeping needle pointing at the corresponding value. The value the guage is displaying could be represented as gallons, lbs of material, or simply 1/8 full, 1/4 full etc..

The "virutal" guage is a representation of the level in the tank. The HMI converts the information from the plc and displays the guage. So the guage resides in the HMI, but the data resides in the PLC.

The guage may be a picture of the tank, a bar graph, or a guage that would look like a fuel guage in your car. How the guage is displayed is done by programming the HMI by selecting "objects" in the HMI setup sofware, and telling the HMI to display the value of that object at the desired scalling by reading the desired PLC memory location.
 
Thank you Elevmike,

That explanation really helped make it clear to me.
Appreciate you taking the time to write that up.

Thanks again.
 

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