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Field inspection manual—volumetric measuring devices

Part 3, section 6— Performance— intermediate flow test

Application

This test applies to any metering device equipped with a register that has a linearization feature, (meter curve correction factors).

Purpose

The accuracy curve of a meter is dependant upon the flow rate. In order to enhance accuracy, manufacturers have introduced a feature that allows meters to be calibrated for different flow rate. Correction factors related to the flow rate can be programmed. In accordance with the requirements, adjacent correction factors may not be set at values that deviate by more than 0.25%. However, the legislation does not impose a limit on the number of set points. Consequently, certain registers may permit the correction of large meter errors using correction factors that widely exceed 0.25%. A meter may appear to be accurate when performing slow and fast tests, but could possibly show large measurement errors at intermediate flow rates if wrong factors have been programmed.

Legislative references

R.262, R.265, R.266, R.267, R.268, R.269, SVM.1-10 and NoA.

Procedure

Set the device to display or print the programmed correction factors. Determined whether there are odd or extreme values that have been programmed at particular flow rates.

Perform an accuracy test at the suspected flow rate following the procedure for a fast flow test.

Record the results.

Interpretation of results

All results must be within applicable tolerances

Revision

Original document

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