need to measure low freq. DC waveform

i need to measure a low frequency waveform from a DC circuit (voltage up to 200mV). I need a sample rate of around 10Hz. to buy an oscilloscope for this is a total overkill. I was thinking of using the soundcard, but then realised it's AC coupled. any suggestions on a cheap method to find this measurement?

Reply to
mattyg1884
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you could use your sound card chopping the incoming signal with a fixed frequency of 10kHz or so, by means of a cmos switch such as the CD4066 (if you need precision, it is better you use one DG411 or one next generation switches with lower RDon resistance). To achieve a good switched signal place one switch in series and one in parallel to the sound card input, and drive the second one with the logic complement of the first. Bye, Massimo

Reply to
Max65

A Voltage to Frequency converter can be as simple as a UJT oscillator IE about 3/4 resistors 2/3 Caps a UJT and a battery or a 555 IC and some electronic glue. CHEAP enough ?

Yukio YANO

Reply to
user

What you want is a DVM.

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Reply to
CJT

I didn't mean to built a voltage to frequency converter (if you want to do it you can use the LM331 that's very linear). I meant to superimpose to the input signal a frequency to allow the sound card to measure its peak to peak value which will be the value of the DC signal. This method was used in early networks analyzers to void the input amplifiers offsets without more complex temperature compensation circuitry. I don't believe he need a simple DVM, maybe it could be enough a logging DVM instead. Massimo

Reply to
Max65

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