Hi
I'm trying to make circuit to measure resistance of probe in liquid.
EC if being exact.
I have set up series of op-amps to generate clean sine wave.
and my output sine wave range from 0.055 V ac to 5 V (Peak, not RMS but i guess it makes no difference .. i have to pick one and go with it)
Frequency between 1khz to 2khz i can go up if needed but not much down...
Well everything is great except i can't convert AC to DC to input it to 12 bit ADC
Right now i have rectified ac output to full wave pulsating DC same amplitude (very close)
but I'm stuck with it ... i tried all kinds of capacitor filters to smooth it out ...
but it signal looses it's amplitude so i get false results ... plus the adc can't get steady measurement ... so here I'm am...
Here what I'm thinking please help me out here:
option 1: go with square wave from the beginning so then i rectify it, it will be very constant reading .... But i don't know how will it impact the accuracy of the measurement of EC (electrical conductivity of liquid)
option 2: convert output sine wave to square and then rectify and be like option 1 but sine wave to take measurement ...
i think option 2 is best but i don't know.... how much results be different after sine to square conversion ... I'm trying not to lose my accuracy at every single part of circuit
I have read on this forum thread http://forum.allaboutcircuits.com/showthread.php?t=5294
but i can't understand the schematic included ...
specifically the analog switches .. and the values to use ... for resistors and capacitors ....
maybe someone could give me a different schematic or clarify this one
PS: my Freq is 1-2khz ... i tried 20khz at first and i had problems with gain ... it wouldn't be even close ... what is the Magic freq for op-amp i have TL062CP Texas instrument ... ?
I have looked up data sheet ... but couldn't understand it ... what is it called what I'm looking for ?
Higher the freq the better (supposing) is the measurement from probe...
sorry for so many q's .. but I'm lost right now
Thank you ....
It's nice to join this community ...
I'm trying to make circuit to measure resistance of probe in liquid.
EC if being exact.
I have set up series of op-amps to generate clean sine wave.
and my output sine wave range from 0.055 V ac to 5 V (Peak, not RMS but i guess it makes no difference .. i have to pick one and go with it)
Frequency between 1khz to 2khz i can go up if needed but not much down...
Well everything is great except i can't convert AC to DC to input it to 12 bit ADC
Right now i have rectified ac output to full wave pulsating DC same amplitude (very close)
but I'm stuck with it ... i tried all kinds of capacitor filters to smooth it out ...
but it signal looses it's amplitude so i get false results ... plus the adc can't get steady measurement ... so here I'm am...
Here what I'm thinking please help me out here:
option 1: go with square wave from the beginning so then i rectify it, it will be very constant reading .... But i don't know how will it impact the accuracy of the measurement of EC (electrical conductivity of liquid)
option 2: convert output sine wave to square and then rectify and be like option 1 but sine wave to take measurement ...
i think option 2 is best but i don't know.... how much results be different after sine to square conversion ... I'm trying not to lose my accuracy at every single part of circuit
I have read on this forum thread http://forum.allaboutcircuits.com/showthread.php?t=5294
but i can't understand the schematic included ...
specifically the analog switches .. and the values to use ... for resistors and capacitors ....
maybe someone could give me a different schematic or clarify this one
PS: my Freq is 1-2khz ... i tried 20khz at first and i had problems with gain ... it wouldn't be even close ... what is the Magic freq for op-amp i have TL062CP Texas instrument ... ?
I have looked up data sheet ... but couldn't understand it ... what is it called what I'm looking for ?
Higher the freq the better (supposing) is the measurement from probe...
sorry for so many q's .. but I'm lost right now
Thank you ....
It's nice to join this community ...