how to avoid the interferential signal? i cannt get a flowing line now.

[聂英]

hi,i just use Labview to write a program which watches the hydraulic pressure. The hydraulic pressure's device makes current from 4mA to 20mA, and it equals 0MPA to 2Mpa. i used a circuit which transfer current to voltage(0-5V), i.e. 4mA-20mA<->0V-5V. and i watch the transformed voltage from the oscillograph . and the voltage is a DC voltage. but when i use the data acquired card to acquire the voltage and read it from labview program, i meet a problem. The signal i watch from labview is interfered. when i acquired a pressure about 0.8MPa, the chart doesnt show a flowing line,but a flexural line. the data is from 0.81Mpa to 0.90MPa. i think the signal is interfered. how can i solve this proble through labview?

[GerdW]

Hi,

you're worried about a 80kPa variation on a sensor with a 2MPa range?

What's the resolution/scaling of the scope?

How accurate is the "circuit which transfer current to voltage"?

[NIquist]

Your scope may also default to a fast averaging sampling mode which would reduce the signal noise and make it appear flatter.