Work with the delta calculation

The following methods are used to calculate a delta.

To calculate the delta

Method 1: If the new counter is higher than the previous (last good) counter

1. To find the volume delta, minus the new counter from the previous counter.

2. Apply the reasonability criteria.

Method 2: If the new counter is less than the previous counter being used

There are three possible reasons why a good, new counter is less than the previous counter:

• A counter rollover has occurred. The counter reached a fixed maximum and then began counting again from zero.

• A counter reset has occurred. The counter began counting again from zero without having reached any fixed maximum.

• The counter went backwards due to a flow reversal.

Assessing the counter and the volume delta is done as follows. The rollover applied in this example is the configured Input Rollover.

3. Calculate a delta applying the rollover. Delta = (rollover – prior counter) + new counter.

4. A rollover occurred and the delta calculated in step 1 is used if the following happens:

   1. The delta is less than half the size of the rollover.

   2. The delta is reasonable.

5. A counter reversal occurred if the following happens:

   3. The delta is greater than or equal to half the size of the rollover.

   4. The delta is reasonable. In this case the delta used is the delta calculated is step 1 minus the rollover.

      Note: This delta will be negative.

6. A counter reset occurred if the following happens:

   5. Assuming a delta equal to the new counter, the delta is reasonable and will be used.

7. If steps 1–4 fail, the delta is considered unreasonable.