how to save the first data within for loop

[watha2]

Hi,

My project is to make a measurement system.

So the system is divided into two subsystem, they are manual system and automatic system.

I need to measure the voltage and the current. However, the current is given by the first voltage in loop then divided by the resistances given from digital potentiometer. So I think that i need to save just the first output voltage when the voltage is maximum to be used for the current. I want to get the current real time.please help me.

[Yamaeda]

Measure the first voltage before the loop?

/Y

[pjr1121]

If I understand you correctly, you are sourcing Voltage, and measuring resistance in order to calculate current.  If voltage is known at all times, why do you need to store it?

Besides that point, you can quite easily store a value from a specific iteration in a control.  Compare the iteration value to zero and wire the boolean result to a case statement.  If iteration equals zero, wire the voltage value to a control.

[watha2]

I couldn't use 2 visa read in one vi. So I don't know what to do.

[pjr1121]

My point is that you are sourcing voltage, you don't need to read it.  You should be setting the voltage in order to use Ohm's Law.

[watha2]

Em, The resistance is the input, so I always know the resistance, the measurement variable is the voltage. I got the current from divided the first output of voltage when the resistance is max and the resistance that i give. I need every value of the voltage when the resistance is changed, but I also need the first voltage to be stored and used as a constant value to  be devided with whichever input resistance i give so i can get the current.

I don't quite understand what you mean. Please explain more to me. I'm sorry if I didn't understand because I'm a beginner. Thanks for replying my post.