Active Physical Channels Property

[JanEgilGlaestad]

I am using the "Active Physical Channels Property" (function?), to get the possible measurement types from the selected daq-card. when i have selected NI9203, the function returns an array with only one entry, current. this is as expected. But when i select a NI9215 card the function returns many possible measurement types, current, voltage, RTD etc. However the datasheet only mentions voltage. Why is this?

[ikaiser · Accepted solution]

Hello Jan,

I'l try to shed some light onto your question.

It has to to how many (most?) physical measurements today are done. Basically the characteristic to measure (strength, strain, acceleration, magnetic field strength, resistance, torque, temperature) is converted to voltage, and that signal is then measured digitally.

You are right about the NI-9215 (and all other pure Voltage Input Modules) - it can by itself only measure voltage. (Side-note: The 9203 does the same, except that it has shunt resistors built in that are used to convert the current input to voltage.)

If you are interested in the 9215's raw voltage value only, use the "Voltage" entry. If you have external circuitry to convert other signals (e.g. a shunt resistor to convert current to volts), you can use DAQmx's comfort functions to scale the values "back" to the original dimension.

Does this answer your question?

[JanEgilGlaestad]

Thanks, then i understand. By that philosophy i wold have thought current input (NI9203) could be a range of measurements, but i guess voltage is more common.

[ikaiser]

Hey JanEgil, thank you for your very quick reply!