Discrepency between consumption data. smart meter V inhome display.at

[champagnecharly]

Current reading x voltage reading on meter is significantly more than usage in watts on the IHD.
I checked the current through the tiils with a clamp meter and reading agrees with the smart meter.
Why would these readings be different.
Currently with 240v 1.3a which would be 320w but Ihd says 220w.

That said at higher consumptions around 1.8Kw the readings correspond.

I also have an inverter connected with current clamp but that reads the same as ihd.

Can anybody shed some light on why recorded consumption data can vary so much between devices. Is this normal?

 

[Geoff1946]

Power factor issue maybe? The small loads are perhaps capacitive coupled PSUs. Just a guess.

 

[binky]

Some things are calibrated, some things are indicators and not always accurate.

 

[GM at CA UK]

I have seen this before where it was due to the inability of the IHD (or rather the current clamp feeding it) to measure all of the current that was being consumed. In that case the IHD clamp had a poor frequency response (lower cost) and did not include the higher frequency currents (harmonics) in its measurements. Nowadays, when an installation is only consuming small currents they are often made up of loads with high harmonic content (LED lights, IT equipment, Power Supplies, etc.). When you are running at 1.8kW I'm guessing there are probably larger "non-linear" loads connected (heating elements, directly coupled motors, etc.) that don't produce many/any higher frequency harmonic currents that the IHD clamp can miss. With the larger loads connected the harmonic content of the smaller loads becomes proportionally less significant and the difference in readings diminishes, as you saw. One of our customers made a video that shows the big difference in readings across a selection of clampmeters in the presence of high harmonic currents. The clamp that comes with your IHD, and even the IHD itself, are probably not the greatest items when it comes to frequency response, and that being the case will also read low in the same way the various clamps in the video do. You can see the video here

 

[BorisJ]

Current reading x voltage reading on meter is significantly more than usage in watts on the IHD.

Watts is NOT current x voltage.

It is watts = current x voltage x power factor.

 

[champagnecharly]

Power factor issue maybe? The small loads are perhaps capacitive coupled PSUs. Just a guess.

A direcrion to read up on. Thanks.
There are no audio amps. Not sure what other devices use cap coupled psus. But different cirxuits therefore devices will react differently or give varying levels of discrepency.

Watts is NOT current x voltage.

It is watts = current x voltage x power factor.

Thanks I was going o th basis of watts law P=IV. But how will power factor come into it on grid supply alone?

Some things are calibrated, some things are indicators and not always accurate.

That I get what I don't is that the ihd only reads data from the smartmeter. Agreed the inverter is not calibrated or calibrated Chinese style

The clamp that comes with your IHD, and even the IHD itself, are probably not the greatest items when it comes to frequency response, and that being the case will also read low in the same way the various clamps in the video do. You can see the video here

J really need to sit and digest your reply and read/learn. Thank you!
One point though is the ihd is the one which talks to the smart meter directly without an additional clamp. And it is for that reason I am so confused.

 

[GM at CA UK]

J really need to sit and digest your reply and read/learn. Thank you!
One point though is the ihd is the one which talks to the smart meter directly without an additional clamp. And it is for that reason I am so confused.

Ah I see. Sorry, I thought the IHD may have had its own clamp. If, as you say, the IHD talks directly to the smart meter its hard to see how or why it would display a different reading. It will be interesting to see what the answer turns out to be.

 

[champagnecharly]

Ah I see. Sorry, I thought the IHD may have had its own clamp. If, as you say, the IHD talks directly to the smart meter its hard to see how or why it would display a different reading. It will be interesting to see what the answer turns out to be.

I may be wrong with the assumption that the same data shown by the meter is sent to ihd. There may be an seperate iternal isolated circuit which provides that obtains data. I say this because with my inverter on and feeding in my ihd reading was 0+/-15w but the meter reported 1.4 amps. @243v

one thing that has made a big difference in the accuracy of my inverter supply (although that wasn't the real cause of confsion) is turning off my 110v inverter, if I get bored I may go round and find the other culprit devices. For me however the leds do not cause an issue I wonder if its down to the transformer that powers some leds.

 

[champagnecharly]

I may be wrong with the assumption that the same data shown by the meter is sent to ihd. There may be an seperate iternal isolated circuit which provides that obtains data. I say this because with my inverter on and feeding in my ihd reading was 0+/-15w but the meter reported 1.4 amps. @243v
one thing that has made a big difference in the accuracy of my inverter supply (although that wasn't the real cause of confsion) is turning off my 110v inverter, if I get bored I may go round and find the other culprit devices. For me however the leds do not cause an issue I wonder if its down to the transformer that powers some leds.