Hi All,
I'm trying to measure the current drawn by a DC pump. I have a 5A, 100mV shunt resistor in series with the pump's power lead. I am reading the voltage across the shunt using a differential input on a 9205 NI A/D card.
With the pump off I can reliably read small DC voltages across the shunt.
When the pump motor is on it generates a lot of electrical noise. The pump has onboard power electronics that allow speed control with a 0-5VDC input signal. I have no details on how the internal power electronics works.
On the scope I saw .4V ptp noise, quite large compared to the .1V signal max. I'm trying to measure. On the Labview end the raw readings are all over the place, I can only get a somewhat accurate answer by using a large sample moving average, but that really slows the response time and still does not result in an accurate enough reading.
Does anyone have any suggestions as to what to try RE hardware or software filtering to get a better signal? Maybe trying to use a shunt here with so much noise is a lost cause and I should try a different type of sensor? I don't have a spectrum analyzer handy so haven't looked at the noise in the frequency domain yet, but could get a hold of one if anyone thinks it may be a narrow set of noise signals from the pump power electronics.
Thanks for any help,
Fastwalker
I'm trying to measure the current drawn by a DC pump. I have a 5A, 100mV shunt resistor in series with the pump's power lead. I am reading the voltage across the shunt using a differential input on a 9205 NI A/D card.
With the pump off I can reliably read small DC voltages across the shunt.
When the pump motor is on it generates a lot of electrical noise. The pump has onboard power electronics that allow speed control with a 0-5VDC input signal. I have no details on how the internal power electronics works.
On the scope I saw .4V ptp noise, quite large compared to the .1V signal max. I'm trying to measure. On the Labview end the raw readings are all over the place, I can only get a somewhat accurate answer by using a large sample moving average, but that really slows the response time and still does not result in an accurate enough reading.
Does anyone have any suggestions as to what to try RE hardware or software filtering to get a better signal? Maybe trying to use a shunt here with so much noise is a lost cause and I should try a different type of sensor? I don't have a spectrum analyzer handy so haven't looked at the noise in the frequency domain yet, but could get a hold of one if anyone thinks it may be a narrow set of noise signals from the pump power electronics.
Thanks for any help,
Fastwalker