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First time setup, Picolog1012 to measure 230V sources

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First time setup, Picolog1012 to measure 230V sources

Postby hybrid » Mon May 29, 2017 12:23 pm

Hi there,

I've just acquired a Picolog 1012, this is my first time using it so would really appreciate any help. I need to measure the voltage and frequency of a 230V source. I'm going to be measuring the frequency and voltage drops as a step load is applied.

So my plan is to step down the voltage from 230 to 12V AC using a simple toroidal transformer.
Something like this http://ie.rs-online.com/web/p/toroidal- ... s/3616210/

I then need to use a voltage divider plus offset & scaling circuit to being the 12V AC down to 0 -2.5 V. Basically like the example circuit given in the pico manual. Which I've uploaded here http://imgur.com/a/YLTVT

What size resistors should I use as R1, R2 and R33?

I suppose first questions is, is this possible? correct ? safe ?
If not how do you recommend achieving what I want to do.
hybrid
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Re: First time setup, Picolog1012 to measure 230V sources

Postby Gerry » Thu Jun 01, 2017 7:10 am

Hy Hybrid,

First of all from a safety perspective, if the 230V source is essentially mains voltage, you would be dealing with potentially hazardous voltages on the primary, and potentially high currents on the secondary, so you would need to have knowledge/experience of the safety protocols relevant to your organisation/application when working with these types of voltages and currents or work with someone who has that knowledge/experience.

To log the data you should be considering a data acquisition device that will give you protection in terms of making connections to it because a Small Terminal Board could leave potentially dangerous connections exposed. You should be considering something like our PicoScope 4444 (https://www.picotech.com/oscilloscope/4 ... verview?lv) with PicoConnect 422 Passive differential Probes (https://www.picotech.com/accessories/d9 ... tial-probe), which are rated to CAT III, at 1000V.

In what looks like a related help desk ticket you mentioned 3-phase, which would then apply here also. Assuming that you will be taking line-to-neutral measurements (which you typically are in a Y configuration at the user end of 3-phase) then the measurements will effectively be single ended (with neutral eventually being referenced back to ground), so the Passive Differential probe will be just dividing down the voltage (without any need to scale and offset the voltage).

Bear in mind that the 230V voltage source is going to be RMS voltage, so you will be measuring AC peak-to-peak value which will be ±325.3V. The Differential probe then divides this down by 25 to ±13V. In our PicoScope 6 software, the PicoConnect 422 probe will be automatically identified with the Y-axis being appropriately scaled by 25, to show the true value.

If you actually want an RMS waveform displayed you can then create a Math channel that will do this for you. Go to 'Tools->Math channels', click on 'Create', then 'Next', and enter the equation mentioned in this post: post100871.html#p100871. You will also need to adjust the scaling to match what you have, and pay attention to the other caveats mentioned.

Regards,

Gerry
Gerry
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Gerry
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