In article ,
Grunff wrote:

That's a great idea, thanks. 257-414 is discontinued, but there
are quite a few other suitable ones.

I use quite a number of the LA55-P (RS 180-7357).
16-turns of ptfe insulated wire to sense 10Adc
full scale being pulled from a 347Vdc supply.
15-0-15V supplies, with following opamp to provide
the Zero and Gain adjustments.

Calibration can be done off-line, with (say) a
20Vdc source, 2 ohm resistor, and digital ammeter.
Once set up it has a repeatability within 0.25%
(of fsd).

AFAIK, the sum to be done will be something like.

T*(P1+P2+P3.......Pn)
Total Energy = --------------------- Joules.
N

P1(etc) are a series of discrete Power calculations,
taken at time intervals T/N, where T/N is small
compared with T. T/N must also be small compared
to the shortest transient P.

For a 5 minute run, T= 300 seconds, and T/N might
typically be 100uS. This gives N= 3000000, which
is the number of (pairs of?) data points to log.

--
Tony Williams.