Originally posted by: basildeengland1
A question has arisen that when a meter for example flips over the maximum range e.g. from 9999 to 0000 is it possible that this meter may for a short period register an inaccurate reading and later correct itself ?
It is not altogether clear the technical level at which you are asking the question:
"Gas Meters - Principles of Operation"
According to the Centre for Remanufacturing and Reuse the lifetime of home energy meters is between 10 and 20 years.
If this next bit misses the precise technical point of your question I appologise in advance...
Ignoring other factors that affect the performance of a gas meter, like aging, the readings after a wrap around will be just as accurate a reading as before the wrap around. And gas use calculations across a wrap around are just as accurate as they would be if the wrap around hadn't occurred. There is no temporary inaccuracy later to be corrected.
The number wrapping feature on gas or electricity meters is completely independent of the calibration or accuracy of the meter, and is just an arithmetical consequence of storing numbers using a finite number of digits.
If the old meter reading was 9995 and the new meter reading 0005 then the gas used is 10 units. This is as accurate as if the old meter reading was 9985 and the new meter reading is 9995, which is again 10 units used.
If you are unsure can just use a simple algorithm like
[Gas Used] = [New Reading] - [Old Reading];
if Gas Used < 0 (negative) then
[Gas Used] = [Gas Used] + 10000;
The first calculation in the case of wrap around gives
0005 - 9995 = -9990
and correction needed because you have exceeded the maximum stored number is -9990 + 10000 = 10 (your actual gas use)
This is equivalent to temporarily adding an imaginary extra digit incremented to 1 in front of the real digits and doing the calculation
Of course, you don't need to add the extra digit when giving the meter reading to your gas supplier.