Pico Technical Support and Discussion Forum

Tim · User Joined: 03 Apr 2007 Posts: 3

Hi All,

I'm fairly new to this but I'm looking to measure DC power and log the data to a PC. The supply is 18V with PWM and the max current is 9.5A

I think the USB ADC11 will do the job for me with the correct probes but I have a couple of questions.

1. Can I also use the USB ADC11 to start / stop the test via a digital output?
2. Can you recommend a Current clamp & Voltage probe?
3. Can I control the entire testing from Excel?

Thanks,
Tim

ziko · Posted: Tue Apr 03, 2007 10:56 am Post subject:

Hi and thank you for your post.

The ADC11 can measure 0-2.5V, you would need to attenuate your voltage signal, we provide a terminal board in which you can solder some resistors.

1)The ADC11 does have a digital I/O however to use this you have to write your own software.
2)Using the ADC11 and a current clamp you will only measures positive voltages.
3)Yes you can write your own software in excel we provide an example macro when you do a custom installation.

I will need know to what is the speed of the signal you are measuring and how many channels you are wishing to measure. As this may mean if the ADC11 is or is not suitable.

Hope this helps.

Kind regards

Tim · User Joined: 03 Apr 2007 Posts: 3

Thanks for your information Ziko,

I have finally recieved some information from the manufacturer of the components that I will be monitoring.

The PWM frequency for the DC power is 16kHz. I will only be wanting to measure the Current and Voltage from this single source - is it still possible to use the ADC11/12 and can I simply combine the attenuated voltage and the current readings of the readings to calculate the power draw?

I am not needing extreme accuracy but a good result 18V DC 0-9.5A to within 0.1A

Thanks in advance,
Tim

ziko · Posted: Wed Apr 18, 2007 9:40 am Post subject:

Hi,

You are trying to measure a signal that is 16kHz, which in turn means you need to sample 10 times quicker (since it is a square wave). This is beyond the ADC11s capabilities as it has a sampling rate of 20kS/s. In PicoLog there are also a number of factors you have to take into account, this all depends on the mode that you are using.

How long do you want to sample for?

Kind regards

Tim · User Joined: 03 Apr 2007 Posts: 3

Hi,

The time taken for the test is 20s with power measurements averaged over 0.2s intervals.

Is there any way you can see this working?

Thanks,
Tim.

ziko · Posted: Tue Apr 24, 2007 9:16 am Post subject:

Having consider your application. We currently do not have any product that can fulfil all your requirements. The problem is the frequency of your signal and the length of time you are sampling for. If we were to take the 3206 for example, this has a record length of 1MS, you would need to sample 160KS/s for 20 seconds this will give you 3.2MS which is beyond the 3206.

The only product I see that can achieve the majority of your needs is the 520x scopes, however the SDK is not available at the moment and will not be for another couple of months. You will not be able to use excel to create macros for the 520x though.

Hope this helps.

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Pico Technical Support and Discussion Forum