@Tribillowl 👍 - not sure how the IHD can be incorrect, as it's just a "repeater" display for the data on the meter itself.
The meter sends it the kWh consumption every 10 seconds plus the current active ToU tariff rate, so the IHD can multiply them together to display the current cost. So if the meter's sending the correct information I can't see how the IHD can get it wrong 🤔
@geoffers
It gets it wrong by multiplying the wrong set of values.
I suspect the code does something like multiply consumption by unit price where DATE(gmt date time value) = TODAY(), so missing the 23:00-00:00 gmt values for yesterday, that are in fact 00:00-01:00 bst today.
@geoffers
It gets it wrong by multiplying the wrong set of values.
I suspect the code does something like multiply consumption by unit price where DATE(gmt date time value) = TODAY(), so missing the 23:00-00:00 gmt values for yesterday, that are in fact 00:00-01:00 bst today.
Yea, but the GMT>BST adjustment has already been made on the meter, so if the IHD is just picking up the data from the meter there should be no error
Have a look at yours : mine has been corrected for BST...
The SMETS spec states that the meter has a "Local Time Change calendar", and the IDH should adjust from UTC to local time in the summer
@geoffers
That just means the meter has been coded to correctly display GMT/BST.
The data is hopefully some standard format (ISO 8601 or more likely Unix epoch) and it's up to the display / application / IHD to do the conversion when it gets displayed / used in calculations.
A bit of digging and it's sent to the IHD over the HAN as a Zigbee UTCTime:
According to ZigBee Cluster Library [1], UTCTime is an unsigned 32-bit value representing the number of seconds since 0 hours, 0 minutes, 0 seconds, on the 1st of January, 2000 UTC (Universal Coordinated Time). The value that represents an invalid value of this type is 0xffffffffff.
By my maths, that gives us until 2136!
But you're right, anywhere using signed 32 bit ints will have fun come 2038!
A bit of digging and it's sent to the IHD over the HAN as a Zigbee UTCTime:
By my maths, that gives us until 2136!
But you're right, anywhere using signed 32 bit ints will have fun come 2038!
👍 Interesting - the meters themselves (or at least the data accessed from them using the Glow API) uses the Unix time—the number of seconds elapsed since the Unix epoch (00:00:00 UTC on 1 January 1970)
@geoffers Hi, I had wondered if the time change had something to do with it, but the 12-1 bar is in the light blue, denoting off peak, and is the time I start the charge to the battery, so the app bar chart figures are correct, but the sums are not! Problem is, all data is fed from the meter.
@Tribillowl - Well blow me (the things you do for the benefit of science) - you are absolutely correct.
Although the meter and IHD do show the local time value as BST on their clocks, the tariff rate change occurs as GMT time, changing at 00:30 GMT (= 01:30 BST)
This won't be something EOn can fix - more likely to require a firmware upgrade for the meter (which ain't going to happen)
However it's not worth losing sleep over 😂, since the values on the IHD are purely to give you an approximate idea of your usage costs. Fortunately the billing is calculated correctly from midnight to 7 am local time, summer and winter
@geoffers Hi, thanks for all your input and time on this and, it sort of makes some sense now. Interestingly, I read the post you referenced and I have put a note on there as my Next Drive tariff is showing just the 6.7p as a flatrate on the Glow app and Glowmarkt!
@geoffers Hi, thanks for all your input and time on this and, it sort of makes some sense now. Interestingly, I read the post you referenced and I have put a note on there as my Next Drive tariff is showing just the 6.7p as a flatrate on the Glow app and Glowmarkt!
No probs - I'm interested to fully understand how this all hangs together👍 - Have responded to your other post...
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