Struggling

Hi,

Been looking all over the net and on all the topics, im trying to find help on the following question, much appreciated



When the transducer is measuring 0 mm the output is 0 volts and when it is measuring 100 mm the output is 10 volts. Calculate the accuracy when used in a 6 bit, 10 bit and 12 bit system in mm.

Thanks

That's really easy, but the question is a bit misleading = they are really asking about resolution, not accuracy. Here's an example:

6-bit = 2^12 increments = 64. Over your voltage input range you can therefore measure to 100mm/64 = 1.5mm.

so would i be right in sayin For a 10 bit system, 100mm / 1024 = 0.09765625mm

So for a 10 bit system, the accuracy of the measurement would be: 0.09765625mm

6 bit = 2 ^ 6 = 64
10 bit = 2 ^ 10 = 1024
12 bit = 2 ^ 12 = 4096

Resolution in 6 bit would be 100/64 = 1.5mm
10 bit ==> 100/1024 = 0.0976 mm
12 bit ==> 100/4096 = 0.0244 mm

where does the word lengh come into it

taylor,

accuracy and resolution are not the same thing. Accuracy is the measurement device’s degree of absolute correctness, whereas resolution is the smallest number that can be displayed or recorded by the measurement device.

ok thankyou for you post want to help with rest of the assignment lol

taylorc-

The previous posts are making a VERY important point about terminology. It is not a trivial point. Accuracy and resolution are very different things. If the question was posed as you wrote it then the answer is that you can't make a determination from the information supplied. While resolution can provide you with the minimum possible accuracy it can't actually tell you the accuracy.

If you rephrased the question when you posted it, be a bit more careful next time. In this case it was pretty obvious what you were looking for. Next time it may not be. Incorrectly phrasing your question can get you an answer that has nothing to do with what you want to know.

Keith

Terminology is the key word here...

Resolution tells you the number of divisions over the entire input range, whereas accuracy tells you all about the setup (aka A/D converter) of the analog card.

6 bit converters often have an accuracy of 2 LSB's, 10 bit have 1 bit accuracy and some 12 bit cards do even better than 1/2 bit.

Anyhow, the higher the resolution the more you have to worry about shielding, ducting etc... otherwise you're not better off with a 12 bit card than you would be with a 6 bit (small signal swings would drown in the noise picked up by the conductors).

BTW not trying to be the wiseguy, but...
- 6 bit converter: 10V input returns a value of 63dec -> resolution is 1/63.
- 10 bit converter: 10V input returns a value of 1023dec -> resolution is 1/1023.
- 12 bit converter: 10V input returns a value of 4095dec -> resolution is 1/4095.

3-bit converter

Range 000 to 111 (0 to 7 dec)



Decimal  Binary  Segment

 Value   Value   Number



   0      000

             \_____ 1

             /

   1      001

             \_____ 2

             /

   2      010

             \_____ 3

             /

   3      011

             \_____ 4

             /

   4      100

             \_____ 5

             /

   5      101

             \_____ 6

             /

   6      110

             \_____ 7

             /

   7      111

.
For 3-bit binary numbers, 2³ = 8 means... there are 8 numbers.
However, "0" is one of those numbers!

The number of segments is equal to the maximum value in the 3-bit value which is...
2³ - 1 = 7

The resolution is 1 in 7.