speed

Hi guys

I need to know the fastest plc on the market?

thanks
Jim Cav

The ones on the trains in France\Germany do about 180-200Mph

Speed is irrelevant. What do you want to do, first?

The Tricon by Triconex is one of the most reliable; everything is triplicated.....not sure about it's speed though but I think it would be up there.

My money is on Siemens S7 400

whats the trains name i will check it out, panisonic is saying they have a scan time of 1.9 ms

Speed7 from Vipa claims they are the fastest.

I've been told that Beckoff is less than 1 msec.

Mitsubishi Q series is 34ns per instruction.

Just out of curiosity, why is the speed of the PLC important to you?

Mitsubishi's new iQ series is 4x faster than the old Q.

As mentioned before, speed is irrelevant. It's going to vary based on the command mix and size of the user program. So to simply choose based on the book speed of a single instruction is just stupid. The device should be chosen based on capabilities and most specifically the project requirements.

Buying a PLC based on rated speed is like buying a car for it's color, ignoring the fact that it's on fire and missing 3 wheels.

PC based systems such as the Beckhoff TwinCat operate extremely quickly due to the use of a PC and their EtherCat range scans the I/O very quickly as well.

Of the shelf PLCs may be slower but it as other people have mentioned, why is the speed so important?

As Crossbow has said it is still dependant on the code and amount of it, for the complete processing scan time. Manufacturers documentation normally quotes the figures for each instruction.

Jon.

You must no do anything that requires speed

tomalbright said:

Speed is irrelevant. What do you want to do, first?

Click to expand...

Having special hardware that is necessary too. What difference does it make if the processor is fast but the digital I/O responds in many milliseconds and the analog inputs and output have huge RC filters?

Speed is good but being deterministic important to take advantage of the speed.

The fastest PLCs would be PLC. How can you beat a dual core process with a huge cache? You can slow the PC with a non-deterministic operating system like windows.

S7s are fast. The times claimed for turning and off a bit are very fast. What Siemens doesn't count is all the register shuffling and times wasted openning data blocks. Only about 1 in 2 or 3 instrucitons do real work. This is because it takes multiple instructions do anything because the instructions are only single operand instructions. Normal PLCs have blocks that take several operands so they can take longer to execute but still get the same amount done as three faster simpler instructions.

The biggest question in these cases is "how fast is fast?". As a rule of thumb, an average PLC will get you 2-10ms response time once the system is optimized. Bigger programs will have a longer scan time and smaller programs less. Please specify your application a little further so we can help.

Depends on how fast you throw it