Hi,
I'm thinking about constructing energy monitor for DC circuit. Because I usually prefer non invasive methods I would like to use hall effect CT. Another reason for using it is the current itself. I expect the circuit to work with voltage around 250V and 22 A. Yes there are some shield but I don't trust them when I see those small connection terminals. But back to the question. I plan to measure voltage just by using voltage divider and then measure voltage on it. Power source is "hard" so I'm not really afraid of using such a circuit without some op amp "magic". Current transformer would be connected right to the MCU. But there is the catch.. noise in measured data. Because I'm focusing on long term and relatively precise energy monitor I can't neglect noise. At first I was thinking about just using some digital filter in MCU but more that I think of it I'm leaning to the side of HW filtering. I can imagine low pass RC filter with voltage divider to cut off all AC noise. But I'm not really experienced with using HW filters. Can I go wrong with using too low cutoff frequency? Let's say 1 Hz cutoff for DC should be ok, no? But mainly I'm absolutely clueless if it's possible to create HW filter for hall effect CT. I expect there would be needed some op amp circuit so the low pass filter wouldn't interfere with the measured data from the CT. Any suggestions? Thanks.
I'm thinking about constructing energy monitor for DC circuit. Because I usually prefer non invasive methods I would like to use hall effect CT. Another reason for using it is the current itself. I expect the circuit to work with voltage around 250V and 22 A. Yes there are some shield but I don't trust them when I see those small connection terminals. But back to the question. I plan to measure voltage just by using voltage divider and then measure voltage on it. Power source is "hard" so I'm not really afraid of using such a circuit without some op amp "magic". Current transformer would be connected right to the MCU. But there is the catch.. noise in measured data. Because I'm focusing on long term and relatively precise energy monitor I can't neglect noise. At first I was thinking about just using some digital filter in MCU but more that I think of it I'm leaning to the side of HW filtering. I can imagine low pass RC filter with voltage divider to cut off all AC noise. But I'm not really experienced with using HW filters. Can I go wrong with using too low cutoff frequency? Let's say 1 Hz cutoff for DC should be ok, no? But mainly I'm absolutely clueless if it's possible to create HW filter for hall effect CT. I expect there would be needed some op amp circuit so the low pass filter wouldn't interfere with the measured data from the CT. Any suggestions? Thanks.