Hello
I would like to ask if it needs to do the signal conditioning for entering the analog signal to the microcontroller (Arduino Duemilanove 168) ?
If it does, how to do the signal conditioning ?
Thanks a lot 
OK give us a clue.
What rotational speed sensor are we talking about here?
Ah, sorry
i need to search more information of the sensor
i just know it is an Inductive rotational speed sensor from the ABS
Any links?
What speeds are you trying to measure?
What do you want to do with the results?
When you say ABS do you mean anti lock breaking system?
If so be aware that the processor chip in the arduino is not qualified for automotive use although there are people who use it in this way.
However I would strongly advise you against using this for a safety critical system given that you are having to ask this question in the first place.
Generally passive magnetic type inductive speed pickups are used with some signal conditioning (usually comparator type op-amp) and wired to a digital input as the information you want is the time lapse between pickup pulses. I don't think you would get accurate results trying to process the signal through an analog input pin.
Lefty
Any links?
What speeds are you trying to measure?
What do you want to do with the results?
When you say ABS do you mean anti lock breaking system?If so be aware that the processor chip in the arduino is not qualified for automotive use although there are people who use it in this way.
However I would strongly advise you against using this for a safety critical system given that you are having to ask this question in the first place.
I want to collect the velocity of the motor eventually.
And i want to display and save the velocity of the motor immediately.
Yes, the sensor is from the Anti-Lock Braking System.
This might be applied on the vehicle, but i just would like to know could i do it on this way. The maximum output voltage of the sensor is 5V, and it generates Alternating Current (AC).
If the output voltage does not exceed the operate voltage of the MCU, it will be ok, is it?
If the output voltage does not exceed the operate voltage of the MCU, it will be ok, is it?
yes it will be OK. Even if it exceeds 5V then it is simple enough to clamp it with diodes.
same with the AC part, clamping diodes will prevent the signal going negative. See this page but in your case use a 200R series resistor in place of the 20R one shown here.
http://www.thebox.myzen.co.uk/Tutorial/Protection.html
The problem is when there is not enough voltage, then you have to amplify it and it depends on how big the signal is to begin with as to what methods of amplification will work.
Generally passive magnetic type inductive speed pickups are used with some signal conditioning (usually comparator type op-amp) and wired to a digital input as the information you want is the time lapse between pickup pulses. I don't think you would get accurate results trying to process the signal through an analog input pin.
Lefty
What you are saying is that i should add a Data Acquisition to maximize the accuracy ?
Not sure what you mean by a Data Acquisition, all he is saying is go in through the digital port. For this you need a signal that drops below 0.7V (as it is AC it will) and 3.3V. That will need amplifying if it doesn't.
This is why it is really best to know what is being interfaced before we can describe how to do it properly.
But it is Analog output signal from the sensor. how could the signal go in through the Digital Input directly
The sensor type is a variable reluctance - and there are a few IC designed to work with these.
Maxim make these and they look great - but they are surface mount. I would love to use one of these because they look much more friendly - but as I have no surface mount skills I can't 
Otherwise you are stuck with one of these:
I have got this to work with an Arduino - top tip is to check the polarity of the wires - if it's not working swap them over
James
Oh and if anyone has any clever ideas how to get a surface mount on to a DIP I am happy to hear - I think you can get adapters but they still require you to solder the things.
I even have a load of the ICs... shame they are useless to me
(I really want to use that MAX chip - half the components of the LM one)
But it is Analog output signal from the sensor
No it is not. The ones I have seen give a pulse each time a metal tooth passes over the coil. You are trying to measure the time between pulses therefore you have a digital sensor.
Now if your sensor doesn't work like this we need to know how it works and what you want to measure.
Edit James that link comes up with a message:-
Your require pages is cannot open by blow
Reason : Connect this pages through directly deep link
Have you any idea what that means?
The sensor is analog - but the output from whatever you use to interface is digital. It will pulse on "zero crossing" - meaning that it will output a pulse when the AC signal goes from neg to pos across 0v - if that makes sense (I think that is right - as my memory serves me right)
Hmmm - just Google for "LM1815N" - it was just a datasheet.
No it is not. The ones I have seen give a pulse each time a metal tooth passes over the coil. You are trying to measure the time between pulses therefore you have a digital sensor.
Now if your sensor doesn't work like this we need to know how it works and what you want to measure.
I am pretty sure that it is Analog output signal
The sensor is equipped with two wires only
An analogue transducer is one that gives a signal that is proportional to the effect you are trying to measure. This sensor gives a pulse when a tooth passes in front of an inductor. Therefore this is a digital sensor not an analogue one. The act of using it involves timing the interval between pulses.
The fact that the voltage pulse hight may be dependent to some extent on the rotational speed does not make it an analogue sensor.
An analogue transducer is one that gives a signal that is proportional to the effect you are trying to measure. This sensor gives a pulse when a tooth passes in front of an inductor. Therefore this is a digital sensor not an analogue one. The act of using it involves timing the interval between pulses.
The fact that the voltage pulse hight may be dependent to some extent on the rotational speed does not make it an analogue sensor.
oh my god, i got it wrong....
So, it is a digital. hmm..
If this sensor need to do the signal conditioning ?
Like Lefty said, the accuracy would be low ?