xmen_xwk
Full Member level 3
I have a current sensing resistor of 0.05R at low side of inductive load. The inductive load is being pulsed by N-Mosfet also at low side with 200Hz frequency.
At duty cycle of 46% the voltage across current sense resistor is 25.8mV measured by 2 different digital meters. Since the measurement looks stable I believe they are average of entire pulse period.
So if I'm correct, the current is 0.0258 / 0.05 = 0.516A but if I connect digital current meter at low side of load it shows me current of around 1A. These measurements are different at almost all duty cycle values but if I set the duty cycle to 100%, the sense resistor measurement matches with current meter.
Now, my question is, how do I measure correct current using the sense resistor ?
At duty cycle of 46% the voltage across current sense resistor is 25.8mV measured by 2 different digital meters. Since the measurement looks stable I believe they are average of entire pulse period.
So if I'm correct, the current is 0.0258 / 0.05 = 0.516A but if I connect digital current meter at low side of load it shows me current of around 1A. These measurements are different at almost all duty cycle values but if I set the duty cycle to 100%, the sense resistor measurement matches with current meter.
Now, my question is, how do I measure correct current using the sense resistor ?