Which component to detect any changes on analog circuit?

[eki27]

Hello,

Could you please help me to find the reference of a product able to do the folowing job:

Supervise any voltage change (positive or negative) of at least 10mV on an analog circuit (which can take a variable value from 0V to 1,2V) and produce an output pulse (ideally a 0V for +-300 mS) for each detected changes?

I will use the output of the component to wake another µP which will convert the analog value to numeric...
The input of the component will be connected in parallel with the input of the another µP, the component should therefore been high impedance input.

Thank you in advance for your suggestions and have a nice evening!

Eki

 

[KerimF]

voltage change (positive or negative) of at least 10mV on an analog circuit (which can take a variable value from 0V to 1,2V)

Do you have an idea about the possible highest rate of this change?
Do you think the noise level on this signal will likely not exceed the 10mV step?
Does the source of this voltage have a rather low or high internal impedance?

produce an output pulse (ideally a 0V for +-300 mS) for each detected changes

I think you meant by +-300 ms that the output pulse (low level) duration is about 300 ms and occurs whenever a change is detected.
Does this mean that the monitored voltage will likely not change during this signalling pulse?
If it does, how long would be the minimum time interval between two successive signalling pulse?

Please note that you don't need to answer any of the above questions, I just wrote what I likely ask myself if I would have such a problem to work on :smile:

Kerim

 

[eki27]

Hello Kerim you're right to ask these questions, which I have already thought :

- the highest rate of change should be 1Hz
- the noise could exceed 10mV but only the numeric read cares (I can set the tolerance software side), the risk with the noise will only wake the µP for nothing (its does really not matter in my case)
- The source has a low impedance
- Normally, the voltage could not change faster than 300mS, if it occurs, it can be ignored or the time of the output can be extended of 300 mS, whatever.

Now that you see these answers, could you suggest a component or a family that can do this easily?

Thanks,
Eki

 

[lovexxnu]

does some DAC work for this? maybe you could use the DAC to monitor the voltage and use some microcontroller to program.

 

[FvM]

This sounds like a specification for an analog circuit:
- high-pass to filter out the DC level
- possibly a low-pass to filter out short fluctuations or "noise"
- full-wave rectifier to detect both polarities of voltage change
- comparator with adjustable level
- a one-shot (monoflop) to extend the pulse to 300 ms

The specified circuit would ignore very slow voltage voltage changes. If you sense a fixed voltage difference to the last measured voltage, a digital track-and-hold circuit would be preferable:
- DAC to hold the last measure voltage value, controller by the processor
- differential amplifier to measure the difference between actual voltage and DAC
- low-pass and additional stages as described above