True rms panel meter

[Tammuz]

I'm looking for something to back up my Auber dspr 400. The least expensive unit that has a good rep was the Datakom DA 0101 for about $35 US without current transformer.
Has anyone here a better recommendation?

[BigSwede]

I'm not 100% sure what you desire. If it's a power meter, I've been very pleased with the performance and accuracy of my cheap unit:

bulbs2.jpg

It's a Murata ACM20 Series power meter. Gives you Volts, amps, watts. I've used it for some time without any issues at all. It does use a toroid to measure amperage, but I mostly leave the watts displayed during operation.

Not lab grade, but little of what we do requires much more. HTH

[Yummyrum]

Agree the murata meter Big swede uses is accurate for Phase control but problem with Aubers is they use burstfire power control . Which is great , except because it is turning whole cycles of power on and off over a 2 second time frame , it is a bugger to measure actually measure the power .

I ended up making a true RMS meter that would sample the Voltage over a 2 second period and then perform RMS calculations on the samples . I then calculated the actual power from my elements resistance based on its rated power and operating voltage .

An arse way to do it but it was extremely accurate .

viewtopic.php?p=7787459#p7787459

[Salt Must Flow]

Agree the murata meter Big swede uses is accurate for Phase control but problem with Aubers is they use burstfire power control . Which is great , except because it is turning whole cycles of power on and off over a 2 second time frame , it is a bugger to measure actually measure the power .

I ended up making a true RMS meter that would sample the Voltage over a 2 second period and then perform RMS calculations on the samples . I then calculated the actual power from my elements resistance based on its rated power and operating voltage .

An arse way to do it but it was extremely accurate .

viewtopic.php?p=7787459#p7787459

All of that is way over my head. Just curious ... in the end, how accurate is it to assume that a 240V 5500W element at 50% power is operating at 2750W using one of those Auber units?

I know it depends on the power to the home and not all areas are stable or equal. I also recall you had a unique issue using Auber units due to your solar & battery setup or something like that.

[Yummyrum]

All of that is way over my head. Just curious ... in the end, how accurate is it to assume that a 240V 5500W element at 50% power is operating at 2750W using one of those Auber units?

I know it depends on the power to the home and not all areas are stable or equal. I also recall you had a unique issue using Auber units due to your solar & battery setup or something like that.

Good question SMF and yes it does depend on the voltage at your shed and also how much that drops when your element turns on .In my case there is close to 14V drop between when I turn element on and off .

OK so look at your 5500W 240V element .
I made a calculator .Plugging that in I can see your element has a resistance of 10.42 Ohms

it is from here
viewtopic.php?p=7786460#p7786460

Ignore the Calculate from Current bit , that's just if you are using an ammeter .(The numbers in that block don't change when you are inputting Voltage)

Element 240v.png

Now say your voltage drops to 230 V ,The element is now pulling only 5052w at 100% power

Element 230v.png

If your voltage is only 220v then your element would be pulling 4621w at 100% power

Element 220v.png

So getting back to your question
if your supply voltage is 240v , then yes 50% power is 2750w
but ,if your supply voltage is 230v , then 50% power is 2526w
and if your supply voltage is 220v , then 50% power is 2310w

How much you care about the difference between the ideal and the real is a personal choice
For the most part , it's probably close enough but if you want to know for sure , Turn the controller to 100% power , measure the voltage across the element , then plug that into my calculator to give you the actual 100% power , then you know what percent of what is .

But then , if your street voltage is changing through out the run , so will your actual power

[shadylane]

I then calculated the actual power from my elements resistance based on its rated power and operating voltage .

An arse way to do it but it was extremely accurate .

There's a problem with trusting the rated power of elements.
Seems like the majority of the elements I've tested have a slightly higher resistance than the math would say even at room temperature.
After being brought to temp and measured the resistance is even higher. Usually around 10% more than it should be.

An example would be a 5,500 watt element should be around 10.5 ohms but is 11.5 ohms at operating temp.
Now the power is only 5,000 watts.

[Windy City]

This is the one I use.
https://www.digikey.com/en/products/det ... WQQAvD_BwE

Here is the data sheet.
https://www.selec.com/us/en/viewdocumen ... 55b2ba2521

Not necessarily cheap but gives a ton of feedback/information.
To be honest I ended up using it to save space on the control panel with one meter instead of three, also not a bad price when considering buying three meters, the extra real estate on the panel and the extra wiring.

[Yummyrum]

Windy , I believe you use Auber DSPR1 .( ascertained through squinting at your fine controller build )
Good to hear that meter will work . DSPR 400 uses same burst-fire mode so should work on that as well .

Windy , i see you have three elements . Am I right that you are using one phase of the meter per element ?

Does the meter show a combined total power of each phase ?

I really like the look of that meter .

It also appears to have a seperate power input to run it so it shouldn’t suffer burn out at low power setting like some of the cheaper meters that are self powered of the voltage input .

[Windy City]

Hey Yummy
Yeah good detective squinting it is a DSPR 1
Yes I am measuring by one phase per element. I actually called them to make sure. I hate to open the smoke capsule that is installed on all these electronics.
Yes it will show total power use and much more.
I liked that it had the separate/independent power source knowing that is a weak link in meters.
When you build a complete panel and have your cutouts you are kind of stuck with that sizing and really don't want to have to have to cut out all the nicely bound wires again. I try and find the best product for my use. Yeah it costs a little more but as the old saying goes buy right cry once buy wrong and cry many times.

[Yummyrum]

Awesome . Thanks Windy

BTW , this is gold .

viewtopic.php?p=7753350#p7753350

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