Question asked in an interview, need help.....

What is the maximum integer unit for analog input of siemens 300 plc?

pls help

thank u in advance.

Download and read manual:
S7-300 Automation System Module Data

svk said:

What is the maximum integer unit for analog input of siemens 300 plc?
pls help
thank u in advance.

Click to expand...

Integer unit is always "one".
Probably, you mean integer value?
In such case, read the manual, as Homer suggested.

svk said:

What is the maximum integer unit for analog input of siemens 300 plc?

pls help

thank u in advance.

Click to expand...

the maximum integer unit is 27648 this called the magical number
this number is generated due to analog to digital conversion process for the analog input where if you have a signal with span from 0 to 10 voltage then the conversion inside the CPU act as 0 volt means 0 integer number and 10 volt means 27648 integer number all this should be performed by scaling and unscalling function

Analog Value

This depends on the card resolution, so if it is a 13 bit card it will span only to 8,192, while if it is a 14 bit it will span to 12,288.

It is the direct sum of the straight binary value.

Cheers

So it is either "1", "27468", "8192", or "12288". I am glad that I am not depending on the correct answer.

I suppose because the question said "maximum", then 27468 must be the desired answer.

If the "Overflow" is included then it would be 32767

these kind of questions differ from manufacturer to manufacturer so as others have suggested it is best to read the manuals. But as a general rule of thumb if you find out the resolution to find out the Max values use 2^x-1, x being your # of bits. Also watch out if your data type is for signed and unsigned, usually if its signed the max is halved from the max of what the value would be when unsigned but you can count in both the positive and negative direction for signed where as for unsigned your values would be only positive values.

thank u all for feedback ..

Moggie, from your chart, the "maximum integer unit" (which probably means do not include signs) would be "32768" for the underflow on the last line.

Hello guys;
The original question was:
"What is the maximum integer unit for analog input of siemens 300 plc?"

The question was properly answered by Metwally.Mustafa, and the answer can be found by looking at moogie's table, using the rated range lines. The maximum value that will be returned by a Siemens S7 analog card to the CPU (no matter the resolution, type of signal...) is 27648, which will correspond to 100% of the input signal, 20 mA, 10 V...
Anything above 27648 will indicate overflow or error.
Temperature (RTD and TC) cards behave differently, but this is true for all current, voltage, resistance... analog values.
For a bipolar signal(+/- 10 V for example), the range will be +/- 27648, for a unipolar signal (0-5 V, 0-20 mA) the range will be 0-27648.
This is quite standard wiith Siemens S7 PLCs, and is described in the Module Data manual suggested earlier (Chapter 5, Representation of analog values).
Thank you,
Daniel Chartier

Congrats Dan you got the job!! LOL.

The maximum value that will be returned by a Siemens S7 analog card to the CPU (no matter the resolution, type of signal...) is 27648, which will correspond to 100% of the input signal, 20 mA, 10 V...

Click to expand...

That is probably the desired answer, but notice that the phrase "maximun integer unit for analalog input" does not contain the rest of your phrase "returned by an analog input, and technically does not eliminate any of the overflow and underflow values associated with that very same analog input. There is only one "maximum", but there are several other values in this case (i.e. the "normal" range of values of the analog input, and the maximum value of that normal range.)

I know, I am splitting hairs again, but some interview questions are written only to trip up unsuspecting victims.

A good answer in an interview is "I'm not certain, but I know I can get that information from the manuals. That would be better than guessing".

No interviewer could seriously expect people to recall numbers from memory, and IMHO the above answer is always going to be the correct approach.