Need help: electrical/math

[bunny]

I think i need some reassurance or fresh guidance.
I do not have a True RMS meter.
I'm trying to get to know my element better and it's watt story relative to vapor speed.
My 1500w 120v element meters 10 ohms resistance.
My controller shows amp draw during heat-up and run.
So: ohms x amps = volts.?
If my amps are 5 during my run with 10 ohms resistance does this mean my voltage is 50?
amps x volts = watts.?
If so, then 5 amps x 50v = 250w.?
4.2 amps x 10ohms =42v.?
4.2amps x 42v = 176w.?


Have I got this right or am I way out there in the parking lot?
Thanks for any assistance.

Do I need a True RMS meter?

[NZChris]

If in doubt, I use this.
https://www.calculatorology.com/watts-v ... in%20amps.

[bunny]

OHHHH!
Thank You,
Thank You,
Thank You,

That's perfect!

[acfixer69]

I think i need some reassurance or fresh guidance.
I do not have a True RMS meter.
I'm trying to get to know my element better and it's watt story relative to vapor speed.
My 1500w 120v element meters 10 ohms resistance.
My controller shows amp draw during heat-up and run.
So: ohms x amps = volts.?
If my amps are 5 during my run with 10 ohms resistance does this mean my voltage is 50?
amps x volts = watts.?
If so, then 5 amps x 50v = 250w.?
4.2 amps x 10ohms =42v.?
4.2amps x 42v = 176w.?


Have I got this right or am I way out there in the parking lot?
Thanks for any assistance.

Do I need a True RMS meter?

You don't NEED a true RMS meter unless you got something else that you need to know. The element has the wattage printed on it at a rated voltage. Your voltage can be measured with a cheap meter. The ohms are going to be constant. The only thing you can change is the voltage and the amperage will be the result of that.

[Stonecutter]

This should also get the job done. It’s not as easy as NZC method but it works all the same. Power being watts.

ED904268-34F7-4413-9158-2C1AE04B8A40.png

[shadylane]

Do I need a True RMS meter?

Wouldn't do any good.
The output from your controller probably isn't a sinewave.
Most of the controllers used around here have a sawtooth waveform.
The only exception I can think of, would be a variac transformer.

[Yummyrum]

Do I need a True RMS meter?

Wouldn't do any good.
The output from your controller probably isn't a sinewave.
Most of the controllers used around here have a sawtooth waveform.
The only exception I can think of, would be a variac transformer.

I beg to differ .
A true RMS reading Voltmeter is exactly what is required if you want to read a non-sinusoidal wave form …. accurately .

The question is how accurately do you need to know the voltage ?

This youtube clip is excellent . It shows several voltmeters . Some Averaging , some True RMS as well as an oscilloscope showing the waveform being measured .
It shows a phase controller being adjusted as you see the variations in measurement .

[Stonecutter]

A clamp meter may help give you real time measurements but they’re also not the most accurate. Of course non of this is going to knock it out of park regarding end product. You’ll gain some insight as to the mathematical workings of your rig but that’s about it. It would be like trying to measure btu output on a propane burner during a run…. Not much use in the end.

[shadylane]

Do I need a True RMS meter?

Wouldn't do any good.
The output from your controller probably isn't a sinewave.
Most of the controllers used around here have a sawtooth waveform.
The only exception I can think of, would be a variac transformer.

I beg to differ .
A true RMS reading Voltmeter is exactly what is required if you want to read a non-sinusoidal wave form …. accurately .

Your right Yummy

[Yummyrum]

Your right Yummy

Hee hee , spent too many years chained to a bench looking at CRO’s


Sorry to labour the point but regarding accuracy of measurement .

In the youtube clip , when O’l mate had it turned up full , the voltage reads were very similar . Translated to Power measurements the Power calculated was down to around 97% of the True RMS …. Pretty close , I could live with that

However , when he turned it down to about halfway , the difference was quite large .
The calculated power based on the Averaging meter was only 39% of what it actually was .

So it probably doesn’t matter if you use those numbers yourself .

Where it can become problematic is when sharing power levels on a forum
EG ,“I use a 5500w to heat up but I have to turn it down to 900w otherwise it floods “ we all scratch our heads wondering why a 2” column is flooding at 900W when in reality its running closer to 2400W… and no wonder its flooding .

I have never fully believed quoted power numbers from a Phase controller for good reason.

[The Baker]

You can see why I call for the electrician.

Geoff

[bunny]

Oh Oh Oh No-

I was most grateful and thrilled by NZChris's post.

Then I watched Yummyrum's video followed up with his video on TRMS clamp meters.
Now I don't know how accurate or not my Amprobe is when it reads 5A.

How can I tell if my controller is sinusoidal or suicidal?
It's similar to this one except the fan is on the inside of the enclosure.

image.png (86.67 KiB) Viewed 1376 times

[Yummyrum]

Its just a bog standard phase controller just like the one in the video . 99.9% of them all work that way .

So alas , if its not a true RMS meter ( whether it reads Volts or Amps ) it will not give an accurate measurement of that definitely non sinusoidal waveform coming out of that controller .

If you are concerned , you could buy ( they aren’t that dear anymore ) or borrow a multimeter that does have True RMS and plot a graph compared to your meters reading . Then you just use the graph in future .

[bunny]

Its just a bog standard phase controller just like the one in the video . 99.9% of them all work that way .

So alas , if its not a true RMS meter ( whether it reads Volts or Amps ) it will not give an accurate measurement of that definitely non sinusoidal waveform coming out of that controller .

If you are concerned , you could buy ( they aren’t that dear anymore ) or borrow a multimeter that does have True RMS and plot a graph compared to your meters reading . Then you just use the graph in future .

Thanks,
Now I know I need the TRMS meter.
I'll probably go for the Klein CL600

Thanks again ,
bunny

[Yummyrum]

I believe these Murata panel mount True RMS current meters have been recommended before .

Note : there are two versions. AC3 requires a 110v supply where as the AC4 version is for 240V

Edit : there are several versions which cover different current ranges too …. Download pdf data sheet from the link for more info

https://www.x-on.com.au/mpn/murata/aca2 ... gKrhvD_BwE

murata have been making high quality meters for at least 50years

[bunny]

I believe these Murata panel mount True RMS current meters have been recommended before .

Note : there are two versions. AC3 requires a 110v supply where as the AC4 version is for 240V

Edit : there are several versions which cover different current ranges too …. Download pdf data sheet from the link for more info

https://www.x-on.com.au/mpn/murata/aca2 ... gKrhvD_BwE

murata have been making high quality meters for at least 50years

Thanks Yummyrum,
This panel meter looks great, however the shipping is such to me that I was able to get the Klein CL600 delivered for a couple bucks less.

The CL600 arrived last night .
The measurements I have taken are vastly different than with my non-true RMS meters.
The assumed wattage calculations were about half as much as with the True RMS meter.
5.0 amp x 50 volt was about 250 watts. The True RMS readings at the same setting were 7.4 amps x 76.6 volt amounts to about 567 watts.
The vapor speed calculator went from 14.57ips to 33.4ips.
No wonder my column could flood near that setting.

I made a cross reference chart so I can still use the old panel meter.

Thanks again, and hope others will frequent the MultiMeter Channel for some first hand information.

[Yummyrum]

Good stuff Bunny .