Measuring RMS current / voltage 2

[heaterguy]

We are using a solid state relay to control current / voltage to a resistive load. 480V single phase.

Using a Fluke meter, is there a way to determine the RMS current / voltage?

The meter bounces around. For instance, it will show 0.95 amps to 1.11 amps. Is the mid-point the rms current? The meter will also give a peak amps. If we divide the peak amps by 1.414, is it equal to the rms current?

TYIA,

Heaterguy

 

[itsmoked]

I have no direct experience with it/them. I despise companies that demand information from ME before they will give you specs of their device... In fact that is enough of a reason from me to shop elsewhere.

It does look like it covers everything it may be more than you need.

I would just go to the local electrician supply place and find an electronic "house" meter. Buy the matching socket for it and wire it up.

 

[ScottyUK]

Have a look at

http://www.keithley.com/products/dmm/?mn=2000

This instrument measures true RMS and can average multiple TRMS readings. Averaging is user-defined for number of samples and sample rate. HP / Agilent's 34401A is a similar meter with similar features. Both are nice instruments. Retail new is about £650, but there are plenty available on the surplus market.

If you're intent upon a power meter, Yokogawa's WT series are reasonable. Voltech Instruments have some excellent products - their PM3000 is a very capable power meter, although it is no longer young and this shows mainly in the user interface rather than the measuring ability. Your application shouldn't prove too challenging for either manufacturer. Voltech's applications guys are ok to talk to; I haven't used Yokogawa's tech support for test gear.

http://www.voltech.com/products/pwr_anl/pm3000/index.htm

http://www.yokogawa.com/tm/wtpz/wtpz/tm-wtpz_01.htm

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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[heaterguy]

itsmoked, Go to this website for more information on the ION:

http://www.k-tech.com/ION/ION-6200-PriceList.htm

ScottyUK,

Those table top type meters may be our next choice. We are looking for devices that can be panel mounted first, hand held second, and table mounted last. And we are looking for a low cost device.

 

[ScottyUK]

Hi heaterguy,

Another thought I've just ahd is GE's PQM meter. It is panel mounting and has a lot of capabilites which used to be the domain of bench instruments. I do not know much more about it - it is a fairly new addition to our site and I haven't had a chance to play with one yet.

http://www.geindustrial.com/cwc/products?pnlid=6&famid=20&catid=60&id=pqm&lang=en_US

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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[heaterguy]

ScottyUK, that's way more than we need. What do you think of the ION?

itsmoked, we called the local electronics store and they recommended Grainger. Can you check

http://www.grainger.com

for a power meter that is 480V?

cheers,

Heaterguy

 

[ScottyUK]

I think it will struggle with the horrible load you have got.

Northern Design in England make a fair range of relatively cheap meters. They used to be very clued up technically - if you can get in touch and describe your application and maybe point them to the discussion in this thread they can probably suggest something. They may still do semi-custom work if they haven't gotten too big.

http://www.ndmeter.co.uk/prodserv.htm

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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[itsmoked]

1'st choice panel, huh...

This Simpson looks pretty good to me..
Seems to cover all the bases and specifically states that it is accurate with screwy waveforms.

Pretty much can't go wrong with Simpson as far as my experience goes with them.

http://www.simpsonelectric.com/pdf/GIMA datasheet.pdf

Note: The table of what the different models can do.
Grainger carries the G100,G200,G300,G400.

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?xi=xi&ItemId=1613496960&ccitem=

 

[heaterguy]

A guy in our engineering department knew exactly what we needed. Check this out...

http://www.loadcontrols.com/products/upc_products.html

 

[VEBill]

"Three Balanced Hall Effect Sensors Sample Voltage Directly"

Hall Effect Sensors to measure voltage?


"ACCURACY - .5% Full Scale"

I wonder how they do that with Hall Effect sensors and adjustable pots?

 

[ScottyUK]

I lifted the following directly from LEM's website. One way of using Hall Effect to measure voltage:

A very small current limited by a series resistor is taken from the voltage to be measured and is driven through the primary coil. The magnetic flux created by the primary current IP is balanced by a complementary flux produced by driving a curent through the secondary windings. A hall device and associated electronic circuit are used to generate the secondary (compensating) current that is an exact representation of the primary voltage. The primary resistor (R1) can be incorporated or not in the transducer.

Much the same as a standard Hall current sensor, but using a very small current and a lot of turns on the primary winding.


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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[VEBill]

Complicated, but provides isolation. Thanks.

 

[LionelHutz]

I guess I'm not sure what you're looking for. Is this for a production run or for a single use application?

That module could work for what you want but it will require calibration for each installation. If you noticed, the site says it uses 2 pots to adjust the scale so you'd either need to put a known power through it or measure the power at a steady operating point to calibrate it. Each time you change a pot you'd have to calibrate the measurement again. It produces 4-20mA output but you won't know how much power 20mA represents when you adjust the pots. Also, that module says 5hp to 150hp. That's 3750W minimum. What size is your heater?

What kind of scope do you have?

 

[itsmoked]

Great points LionelHutz..

I think it's over kill and a pain-in-the-rear for a production application...

 

[bill318]

If it is just a one time measurement your after you could possibly place your resistive load in a styrofoam container (cheap camping cooler), fill with distilled water and replace the lid. Then poke a good thermometer in the water and run the device for a specific amount of time and then measure the temperature rise. This method does not care what the wave shape is.

Probably not what you are after, but I had to add it to the list as food for thought. ;-)