I have a simple (yet probably stupid question, since my knowledge of analog circtuits is very limited) about voltage dividers.
The final goal is to measure AC current for a mains load; to that end, a Hall 5A sensor (ACS724) followed by a RMS-to-DC (LTC1966) conversion circuit is tested.
It is not working, so I'm breaking down the problems I see.
Here's the first one.
Since I'm measuring AC, the Hall sensor's output should be a voltage proportional to the AC current, offset by Vcc/2, right ? Ideally a sine wave at 50Hz; so I'm trying to feed its output along with Vcc/2 to the next component that has a differential input (the LTC1966.)
On the breadboard, I use a 5V power supply (from a USB charger,) followed by a 3.3V LDO regulator (an LD1117V33) and a 1000uF capacitor.
The voltage divider uses two 10k resistors. On the multimeter, the values look ok (3.3V and 1.65V,) but on a DSO (a Nano DSO,) I get this for the Vcc and Vcc/2 :
It seems very noisy, and I can't see why; everything else is disconnected. I don't expect the value to be mathematically Vcc/2 due to tolerance, and probably the DSO itself is a bit crappy, but:
- Why is this happening?
- What can I do about it?
- Could this have a significant impact on the comparators, or I'm worrying for nothing?