I just purchased a picoscope and note the verticle resolution is listed in bits.  What is a bit when used in this context and how is this relevant to automobile diagnostics?

This is from Pico's Test & Measurement website:

"Resolution and Accuracy

In digital electronics, a signal change of 1% is usually no problem, but in audio electronics, 0.1% distortion or noise can be a disaster. Most modern DSOs are optimised for use with fast digital signals and only offer 8 bit resolution (8 bit ADC), so can detect at best a 0.4% signal change (see table).

With 8 bits, the voltage range is divided up into 256 vertical steps (2^8 = 256). With a ±1 V range selected, this corresponds to around 8 mV per step. This may be adequate for viewing digital signals but leave something to be desired for viewing analog signals, especially when using the spectrum analyser function (if it has one).

For applications such as audio, noise, vibration and monitoring sensors (temperature, current, pressure) an 8 bit oscilloscope is often not suitable and you should consider 12 or 16 bit alternatives.

As for a DSO’s accuracy, it is not usually regarded as too important. You can make measurements within a few percent (most 8 bit DSOs quote 3% to 5% DC accuracy) but for more accurate measurements you should reach for a multimeter.

With a higher resolution oscilloscope, more accurate measurements are possible (1% or better) so no need for the meter!

Oscilloscopes with both a high resolution (12 bits or more) and a high DC accuracy are sometimes referred to as precision oscilloscopes — see our application note on high resolution oscilloscopes and FFT spectrum analysers."


Basically, it is vertical resolution and accuracy.  Meaning the up and down movements, or in other words the dynamic voltage changes.  The quote above mentions 8 bit scopes have 256 steps, and approx. 8 mv between each step on a +/-1 volt scale.  The 12 bit scopes have 4096 steps giving you almost 500 micro-volts (or .5mv) between each step on a +/- 1 volt scale.
That's quite the difference!  Vertical resolution plays out in automotive applications when testing ignition primary & secondary, injector voltage, data lines, etc., etc.

I hope this helps, and whatever I got wrong I'm sure someone will correct me.  ;)

'Bit' is not just an oscilloscope term, it refers to an amount of electronic data and is a standard term.

Bill,

Something that has helped me understand many things a lot clearer is playing with an Arduino.  I am including a link describing how analog read works on this unit. I believe the same basic principle applies for DSO's

http://arduino.cc/en/Reference/analogRead

Being in the Picogroup there are some project boards that might be worth checking out as well.

Sam

Bill

In computer speak a single bit is an actual piece of hardware that has two possible values 0 and1.

Every time you add another bit you double the number of possible values.

in binary 0=0, 1=1, 10=2, 11=3; that is four possible values in two bits.
100=4, 101=5, 110=6, 111=7; three bit adds four more possible values for 8 total

11111111=255 so when we include 0, eight bits has 256 possible values (there are 256 combinations of 1's and 0's in eight bits)

So eight bits is like a ruler with 255 marks on it (we don't have a mark at 0)
Ten bits would be the same ruler with 1023 marks for 1024 measurements
and Twelve bits puts 4095 marks for 4096 possible measurements.

32 bits has 4294967295 and 64 bits has 18446744073709551615

What is a bit when used in this context

So I have no idea why they don't just give us numbers that we can understand

and how is this relevant to automobile diagnostics?

back to the eight bit ruler with 256 measurements.
Half the range is above 0 and half below
so When the scale is set from 0 to +/- 500mv there are only 128 steps from 0 to +500mv or about one every .004mv

The big difference is when you zoom in on the wave form it looks like steps; the higher resolution has a whole bunch of little ones, low resolution fewer and bigger.

Jim

to add to jims post, binary works by adding all the numbers for the positions for the bits that are set for what they represent, for instance
  1   0   1   1  0  1  1  0
128 64 32 16  8  4  2  1
----------------------------
2+4+16+32+128= 182

so 10110110 = 182
  below is 12 bit
notice its the power of 2
2048,1024,512,256,128,64,32,16,8,4,2,1

I remember learning that digital meant that any integer used by a computer was going to be either a one or a zero because it was not possible to create hardware that contained all the individual integers. Hence the use of ones and zeros to address any integer in the numerical system.