Shunt Current Sense, high-side vs low-side
20 parts
The same 2A load current is measured twice: across RsH on the high side (near 12 V) and across RsL on the low side (near ground), each 10 mΩ into a gain-50 difference amplifier (0.5 V per amp). The high-side amplifier's Rb1 is deliberately 1% high (50.5 kΩ, not 50 kΩ); that small mismatch turns the 12 V common-mode voltage into an error. Open "load" to see what each reads with no current at all. Real systems: at 100 A the same 10 mΩ shunt would dissipate 100 W; real packs use 50–500 µΩ shunts and higher gains, where the common-mode error matters even more.
- V12 12V
- RsH 10mΩ
- load closed
- Rload 6Ω
- RsL 10mΩ
- U1
- Ra1 1kΩ
- Rb1 +1% 50.5kΩ
- Rc1 1kΩ
- Rd1 50kΩ
- U2
- Ra2 1kΩ
- Rb2 50kΩ
- Rc2 1kΩ
- Rd2 50kΩ