[P102] PZEM004Tv3 change Wh to kWh

[chromoxdor]

I found it misleading, that the value name is called Energy_Wh since the value is in kWh
Took me a while to figure out why the formula %value%/1000 didn´t give me the expected kWh value.

Can anybody confirm or do i have maybe a different revision of this device?

[TD-er]

Some energy meters do only show "Wh" values upto some value and then switch to kWh.
If we always get kWh counts from this sensor, then it is OK to change it.
However if it only switches to kWh after some count, then it may need some reconsidering.

[chromoxdor]

Some energy meters do only show "Wh" values upto some value and then switch to kWh.

I did a bit of research and at first glance it seemed to be like that....
But then i found this in PZEM004Tv30.cpp

/*! * PZEM004Tv30::energy *
 * Get Active energy in kWh since last reset *
 * @return active energy in kWh*/
float PZEM004Tv30::energy()
{
    if(!updateValues()) // Update vales if necessary
        return NAN; // Update did not work, return NAN

    return _currentValues.energy;
}

[chromoxdor]

forgot to attach that:

_currentValues.energy =  ((uint32_t)response[13] << 8 | // Raw Energy in 1Wh
                              (uint32_t)response[14] |
                              (uint32_t)response[15] << 24 |
                              (uint32_t)response[16] << 16) / 1000.0;

[TD-er]

Ah so the output is indeed kWh and not Wh.

Strange byte order by the way.

[chromoxdor]

Strange byte order by the way.

I wish i could agree but I am working right now to understand what this bit shifting means anyway. :)

[TD-er]

Bitshift is literally what the name suggests.

Thus 0010 << 1 = 0100 You literally shift the bits by N places.

So let's assume the response bytes have the hex values 0x13, 0x14, 0x15 and 0x16 on those positions in the response array, then the value becomes:
0x15161314

So there's a rather strange bit order.
It looks like it is little-endian and big-endian mixed.

It is probably OK, but still looks a bit 'odd'.

[chromoxdor]

Minutes ago i asked chatgpt why it is strange :)

[TD-er]

Ah glad to see chatGPT also understands why things might look strange :)