Need help with measure AC current

[Thang Nguyen]

I am working on a project with requirement of measuring current. The system includes both the AC current transducer CR4211-15 (Input 0/15AAC, Output 0/10VDC) and a Fluke i5S (Input 0.01/5AAC, Output 400mV/A).

 

I use cDAQ9184 with NI-9205. I tested with a light and using MAX to monitor the signal but the signal really noise from the AC transducer and clamp. 

Please take a look at the pics I attached which is the screenshot from MAX.

 

I hope anyone with exp can give me a help.

 

Thank you!

Thang Nguyen

[Phillip Brooks]

The DC output scale of your transducer is 0-10V and your measured signal is < 500mV (less than 10% of rating), so I would test with a larger load.

 

Upgrade from a 40W bulb to a 150W flood lamp   

[Thang Nguyen]

Philip,

I increase the sample rate and I think I didn't receive a good signal.

 

 

[machyaer]

Hello Thang,

 

if you are testing your system with a 220V lamp to have a not-to-low signal on the transducer you need a 1kW lamp otherwise the measure will be lesser than the 30% of the fullscale of the transducer or, at least, a 150W lamp as suggested Phillip...

 

Check the wiring of the transducer and test its output by using a normal voltmeter... finally check the connection with your card and the settings in MAX....

from the last image you send I saw a differential input settled... isn't it?

 

Max

[Thang Nguyen]

Max,

Yes, it's a differential input.

Since I have just accessed to a scope, and I tested with my current lamp + an industry fan, I got a really good DC signal from transducer. But from Max, I got the same level of peak but the signal still goes to zero as in my first picture. Somehow I get a noise from my card.

 

Regards,
Thang Nguyen

Edited September 25, 2013 by Thang Nguyen

[machyaer]

very strange behaviour...

 

did you check that the 2 inputs you used are the correct ones? (i.e. AI0 - AI8)

 

did you try using another input channel? (e.g. AI1 - AI9)

 

did you groung the COM pin of the board?

 

Max

 

PS: If it is possible try using a RSE connection connecting just the AI0 and the other side to GND and see the difference

Edited September 25, 2013 by machyaer

[Thang Nguyen]

Max,

I tried with RSE connection and it works. Thank you very much!

 

Now with the Fluke clamp. I think it returns AC voltage. Do you have any experience with this?

 

Regards,

Thang Nguyen

[machyaer]

Great  ! one of the problem is solved...

 

for the Fluke I don't think that the output is in AC... I suppose that is in DC and with the data you wrote 0,4V for each Ampere of measurement (e.g. if the reading is 2A the output should be 0.8V) so I think that the same connection of the transducer with a fullscale limited at 2V will be sufficient...

 

let me know

 

Max

Edited September 25, 2013 by machyaer

[Thang Nguyen]

Max,

I tried with RSE but it didn't work.

 

 

Great  ! one of the problem is solved...

 

for the Fluke I don't think that the output is in AC... I suppose that is in DC and with the data you wrote 0,4V for each Ampere of measurement (e.g. if the reading is 2A the output should be 0.8V) so I think that the same connection of the transducer with a fullscale limited at 2V will be sufficient...

 

let me know

 

Max

 

[machyaer]

ok, I checked on the fluke website for the manual of this clamp... and it seems that the output is in AC   ...

 

so if you are a 50Hz power supply connected to you lamp you should have  the same sinusoidal signal on the reading... always referred to the GND...

 

Did you connect the shield of the bnc cable of the clamp to the gnd of the system? (where the RSE reference should also be)

 

Max

[Thang Nguyen]

Max,

I use RMS VI to calculate and get a reasonable value compare between 2 sensor, so now they are good. The AC thing was quite make me confused.

 

Thank you so much for your help!

 

Regards,

Thang Nguyen

[machyaer]

 

you are welcome...

 

regards

Max