Checks on Wattson Accuracy

EricMears

The 'whats in your baseload' thread was drifting a bit OT and I didn't really want to take my thread on the new flashcounter OT either so have started this new thread.


According to Wattson (& my flashcounter) , my 'nett' line went negative just before 9am today

At 08:55:30, Wattson was showing 597W being generated and 582W used and trace has been below axis ever since.

Flashcounter showed last 10Ws import at 08:47:30 so I'll have bought less than 10Ws since then; previous 10Ws import was at 08:42:55. 10Ws in 475 secs is an import rate of 130Watts.

During that period (I exported day in 30s slugs and averaged up 9 of them) Wattson was showing a generation rate of 412W and usage of 601 (net 189W).

According to the inverter generation for 5 min period ending 08:50 was 372Watts (and I'm pretty sure that they really mean 372 Watts rather than 372 watt-seconds in 5 mins)

EricMears

One small clarification:

I have never said - nor would I - that "my Wattson is x% out so yours must be too" !

I'm sure the individual instruments vary considerably. Some might be correct to fourth decimal place; others could be 20% in error. Only way to be sure is to check against something else known to be accurate.

I would however say that a Hall effect sensor is only at best an approximation. If you wanted to build one a bit better you'd need to completely isolate the test area from all extraneous radiation (other nearby cables, microwave in next room, alien transmissions from planet Zog etc. etc.)

Oscargrouch

EricMears wrote: »

One small clarification:

I have never said - nor would I - that "my Wattson is x% out so yours must be too" !

I'm sure the individual instruments vary considerably. Some might be correct to fourth decimal place; others could be 20% in error. Only way to be sure is to check against something else known to be accurate.

I would however say that a Hall effect sensor is only at best an approximation. If you wanted to build one a bit better you'd need to completely isolate the test area from all extraneous radiation (other nearby cables, microwave in next room, alien transmissions from planet Zog etc. etc.)

Just posted some numbers on the Base thread.

Found the shortcut in Holmes to see your base rate..Should have thought of it first time around (true or false):-

Go to History>Energy>select 24 hrs> select date>Slide the bar (r/h/s) down to 4 hours>select the 4 hours that you want to look at> select any days in turn and it will show you the same 4 hrs for the selected date....HTH....:rotfl:

EricMears

Oscargrouch wrote: »

Found the shortcut in Holmes to see your base rate

Will certainly have a look at that later (probably a couple of days later).

At the moment I'm working on a website script to extract my own data from any defined period. That's already working for "last 5 minutes" but I need to amend it slightly to let me choose start & finish times 'on the fly'.

Currently (:eek:) Wattson is showing approx. 630W whilst I'm calculating 570W.

And of course I'm still waiting to be able to calculate total usage over (say) a 7 day period so I can see how my estimates compare with official meter (it's a crying shame they haven't given me one with 3 decimal places )

Oscargrouch

EricMears wrote: »

Will certainly have a look at that later (probably a couple of days later).

At the moment I'm working on a website script to extract my own data from any defined period. That's already working for "last 5 minutes" but I need to amend it slightly to let me choose start & finish times 'on the fly'.

Currently (:eek:) Wattson is showing approx. 630W whilst I'm calculating 570W.

And of course I'm still waiting to be able to calculate total usage over (say) a 7 day period so I can see how my estimates compare with official meter (it's a crying shame they haven't given me one with 3 decimal places )

Agree; my meter is an LCD just the five numbers. I would have to run a test for around a month to get a near comparison.. OH would not be interested.....in doing the surveys...:rotfl:

rogerblack

Oscargrouch wrote: »

Agree; my meter is an LCD just the five numbers. I would have to run a test for around a month to get a near comparison.. OH would not be interested.....in doing the surveys...:rotfl:

Look carefully.
It will also say something like '1000 flashes per kWh'.

This means that at a load of 1kW, it will be flashing once per 3.6 seconds.
100W - per 36.
20W - per 180.

EricMears

rogerblack wrote: »

Look carefully.
It will also say something like '1000 flashes per kWh'.

This means that at a load of 1kW, it will be flashing once per 3.6 seconds.
100W - per 36.
20W - per 180.

That is of course the system my flashcounter uses.

However, I don't think we can expect Mrs O to sit by the meter with a stopwatch at 3am :rotfl:

rogerblack

EricMears wrote: »

That is of course the system my flashcounter uses.

However, I don't think we can expect Mrs O to sit by the meter with a stopwatch at 3am :rotfl:

I've also used the somewhat silly system of pointing a recorder at the light.
Simply place a recorder timed to record from 3AM to 4AM (or whatever) in the cupboard.
Most phones - perhaps with an installable app - can do this.

Oscargrouch

rogerblack wrote: »

I've also used the somewhat silly system of pointing a recorder at the light.
Simply place a recorder timed to record from 3AM to 4AM (or whatever) in the cupboard.
Most phones - perhaps with an installable app - can do this.

:rotfl::rotfl::rotfl: Glad some Have a bigger Anorak than mine......You are of course joking...........:rotfl::rotfl::rotfl::D

P.S. I would be mad to leave a £300 phone outside all night to check a CU meter...Hmmm don't think even my Video Camera (more expensive) records in pitch black....:cool:

Oscargrouch

EricMears wrote: »

However, I don't think we can expect Mrs O to sit by the meter with a stopwatch at 3am :rotfl:

Will give you her e-mail address to ask, in case you have a 'Death Wish'.

EricMears

Oscargrouch wrote: »

P.S. I would be mad to leave a £300 phone outside all night to check a CU meter

Whereas I can afford to leave one 25pence photoresistor and a couple of bits of plastic pipe outdoors all the time (and the other £20 worth is safely indoors).