Signal Conditioning

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electronic switch

I have some random ultralow dc current signal from a sensor output and i want to convert this current to voltage by using integrator circuit.But I am getting difficulty in how,where and what to connect as a switch so that my integrating action should take place for 49 milliseconds and for one millisecond the capacitor should discharge for further integration.Like that for every 50 milliseconds my integrator should work.Please attach the circuit diagram.Answer is needed soon. 

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Current over time is charge, so I would take a nice low bias OP (3fA is a very low number) and build a charge amplifier. the size of the feedback cap depends of the current you need integrate. So what is ultra low current?
The best shortcut switch for a slow 1ms close with minimal charge injection and leakage is a reed relay 🙂

AD or was it maxim or TI? Have a CDC (charge to digital converter) iC .....
Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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The design of such a switch depends on the range of currents you are integrating and on the size of the integrating capacitor. The off-state leakage current of the switch should be much lower than the lowest input current. Of course the input bias current of the integrator circuit must also be low.

 

You may be able to use a simple FET switch or you may need a fairly sophisticated reset circuit, depending on your current range.

 

Will you be controlling the timing from the computer or will this be a hardware circuit?

 

Lynn

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As usual, Henrik presents good ideas. I like the reed relay idea.

 

Lynn

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Thanks Lynn 🙂
Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Henrik AND Lynn:

 

As usual, BOTH of you have very good ideas and suggestions very often.

 

I look up to both of you. Wish I had kept my experience in electronics ongoing, it kinda got detoured . Wish I had more time to tinker around at home too!

 

-Pete

 

 

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"It’s the questions that drive us.”
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