limit for REALTIME (PHPFINA) value

Submitted by mik.open on Fri, 03/04/2015 - 21:45

hi,

I would like to know how large a value for an kWh accumulator can grow, before reaching its own limit?

Thanks

Mik

Re: limit for REALTIME (PHPFINA) value

Submitted by Robert Wall on Sat, 04/04/2015 - 19:32.

I have not checked the source code, my guess (and it is just that) is it's a long integer, so 2³¹ - 1.

Re: limit for REALTIME (PHPFINA) value

Submitted by mik.open on Sat, 18/04/2015 - 08:01.

Looking at the documentation https://github.com/openenergymonitor/documentation/blob/master/BuildingB... the data is stored in 4 byte worth of data.

The data is written as a binary string (format float) using pack("f",$value).

But I'm still not sure if this representation is https://en.wikipedia.org/wiki/Single-precision_floating-point_format.

Re: limit for REALTIME (PHPFINA) value

Submitted by Robert Wall on Sat, 18/04/2015 - 13:37.

What does the PHP manual say about "pack" and floating point?

Re: limit for REALTIME (PHPFINA) value

Submitted by chaveiro on Fri, 01/05/2015 - 21:02.

PHP size of a float is platform-dependent, 32 or 64 bits.
MySQL we use float with single precision that is four bytes 32bits and this will be the limit.

The answer is tricky because depends on precision of the value that will fit 32bits:

Minimun value: ±1.18×10^-38
Maximal value: ±3.4×10^38

See: http://en.wikipedia.org/wiki/IEEE_floating_point

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