current meter

[gazza48h]

hi all im knew to labview so please bare with me. Im simply looking to take readings such as current and voltage from a 12v bulb and feed them back to a DAQ and onto labview. What components would i need to undergo this. Any help greatly appreciated

[crossrulz]

Use a small resistor that is in series with your bulb.  The size depends on your current.  A 1 Ohm should work if your current isn't very high.  You can then differentially measure the voltage drop across the resistor.  Apply Ohm's Law (V=IR => I = V/R) to get the current.  I recommend using a scale in DAQmx to apply to your current channels.

[gazza48h]

thanks for that information i was thinking of that but the problem is i want to display the amount of energy used to run a 12v bulb on labview. Would i be better in taking in real time data measurements from the bulb or how would i go about doing that?... Or would i be better to stick to Omhs law???

[gazza48h]

thanks for that information i was thinking of that but the problem is i want to display the amount of energy used to run a 12v bulb on labview. Would i be better in taking in real time data measurements from the bulb or how would i go about doing that?... Or would i be better to stick to Omhs law???

[Dennis_Knutson]

You don't make any sense. There are two measurements that you take. Voltage across the bulb and voltage across the resistor. The current is calculated with ohm's law. You then calculate the power from the bulb voltage and the calculated current.

[gazza48h]

Thanks i understand now... Sorry for not making much sense all this very new to me...
Just one more question.... Can i simply take a reading in from just my DAQ connected to labview??

[Dennis_Knutson]

You take two readings. With some basic math, you calculate the current and then the power.

[RTSLVU]

This is probably not the best diagram but you should get the idea...

Use a low value resistor like 0.1 ohm and measure the voltage drop across it.

0.1 Ohm will scale to 100mV/Amp

[Hooovahh]

Also be aware of the fact that if you are using a small resistor (like 0.1 ohm), and your voltage is high, then your power will be high, and the resistor should also be able to handle that type of heat disapation.