How to measure power consumption using GPIB-USB-HS 3458A ?

[swpark]

Hello Folks,

I'm a CS student studying sensor network. I'm trying to measure the power consumption of a sensor using Agilent 3458A and NI GPIB-USB-HS on LabView. I'd like to measure power consumption for a couple of minutes while sensor networks are booted, then try to calculate how much they consume the power.

I've never done power measurement before, However, I tried to setup the environment, and read many posts. However, I'm messed up at setup enviroment. If you have any idea (or script) for calculation of power consumption, and workaround for setup, I would really appreciate and it would be much helpful for my studying.

Followings are what I've done so far.

HW: Agilent 3458A, NI GPIB-USB-HS

SW : Labview 2009

1. Installed Labview 2009 and run "Measurement and Automation Explorer".

2. Enabled NiVisaTulip.dll from NI-VISA-4.5.1 -> Toosl ->NI-VISA -> VISA Option.

3. Observed GPIB-USB-HS under "Devices and Interfaces"

4.GPIB-USB-HS -> Right click ->Click "Scan for instruments"

I got "Instrument 0" with  message "The device did not respond to a *IDN? query" with a beep sound.

When I checked the error message in the panel (Gray+Error), I got "103, "SYNTAX -- *   Expected command header."

So I tried followings

5. Clicked "Instrument 0" and select "Communicate with Instrument".

6. 488-2Communicator pops up -> Clicked "Query" (same as above query '*IDN?')

I got the following message.

iberr = EABO

EABO indicates that an I/O operation has been canceled, usually due to a timeout condition after a GPIB read.  Before reading from the instrument, verify that the GPIB command you are sending is understood by your device and instructs it to place data in its output buffer.  For information on your device's command syntax, consult the instrument manufacturer's user documentation.

Thank you,

Swpark.

[Albert.Geven]

Why did you enable the tulip passport.

probably this handicaps your communication with the NI gpib.

measuring power is measuring voltage and current (or only current when voltage is fixed) and then show this in a graph as a function of time.

[Dennis_Knutson]

The instrument does not support the *IDN? query. It uses ID? You should know that since you have the manual for the instrument, correct?

Ignore the message. There is no problem. From the  Tools menu, select Instrumentation>Find Instrument Drivers and do a search for 3458A. You will get the instrument driver here. On the Instrument Driver Network, you will find information on what a driver is and how to use one.

[swpark]

The reason is that Labview can't get the response from Agilent 3458A so I enabled. Somehow, when I send any query, 3458A responds some numbers. 😞

[Albert.Geven]

Look at Dennis 's post.

Download the driver, select the correct gpib address and make sure that the gpib unit is fixed coorectly to the instrument.

Sometimes the housing is just a little to thick to correctly fit completely.

[swpark]

@Dennis,

Yes, I tried to used that device driver, but "Find Instrument Drivers" can't scan correctly. whenever I scan the instruments, it shows 2 instruments named "?IDN*" and  "2.3....E-02" on the currently attached instruments.Did I something wrong? 

 @Albert & @Dennis,

I have Agilent 6651A as well, while consistent 3V, how can I measure the power consumption? ( Somehow 6651A can respond very well in Labview)

I read the manual, but I don't know how to measure the usage of power for 2 - 3 minutes then draw some graph. Could you give some idea?

Thank you.

[Dennis_Knutson]

There is no such thing as Scan for Instrument Drivers. There is a scan for instruments and you previously said it was okay - just not returning anything for the *IDN? query. It's not supposed to return anything. I also don't know what you mean by 'can't get the response from Agilent 3458A so I enabled'. There is nothing to enable and I don't know what you tried to do.

Do one thing at a time. Before you even open LabVIEW, make sure the scan for instruments works. You should have each instrument on a separate address before doing the scan. You should have only two instruments listed and the only warning you should get is the one that failed to respond to the *IDN?. I would suggest you power down the instruments before doing another scan. If you have a problem with the scan for instruments, try removing the cable from one of them and repeating the scan. If that has problems, swap cables.

[swpark]

I meant I enabled "Tulip Passport". I will upload the screenshot once get school. Thank you so much for your answer.

By the way, could you answer for the 2nd question regarding Agilent 6651a if you don't mind? Is it possible to measure the power consumption for 2-3 minutes using 6651a and to draw some graphs such as current draw periodically?

swpark.

[Dennis_Knutson]

You can probably query it to see what the current output is. Ohm's law says Watts = V*I

[Henrik_Volkers]

Another hint:

Seems like you want to measure really low power devices, µC based, with internal low low power sleep cycles. 

Getting meaningfull data with current measurement in such cases is tricky, involves high amplification, high speed sampling .....  

Easy way: take a capacitor as energy source and  measure the voltage drop and calculate the energy.

However you need to know the capacity, leakage and maybe even soakage of your C. (There ain't no free lunch 😉

Jim Williams from linear has written some great application notes about current measuring . Digg in there and learn. 

Message Edited by Henrik Volkers on 02-08-2010 10:53 AM