Dual pulse input

Despite the fact that true Level A pulse compensation was not possible with yesterday's flow measurement technology, the industry still favors its full implementation as laid down in various standards such as ISO-6551 and API 5.5. In our new Flow-X family, we have realized the complete implementation. 

There are a number of conditions under which the dual pulse output of a flow meter can introduce an error to the connected flow computer. Signal noise, long cables, interference noise and many other disturbances can all introduce errors from either missing or additional meter pulses.  This in turn can cause the flow totals to be calculated incorrectly.

It is an important function of a flow computer to recognize these signal problems from real meter pulses. The ISO-6551 standard, "Petroleum liquids and gases -- Fidelity and security of dynamic measurement -- Cabled transmission of electric and/or electronic pulsed data", and other standards define a standard to deal with and correct for such disturbances.

Below a number of such pulse error conditions are given (the pictures below were taken from a 100MHz digital storage oscilloscoop):

Most existing flow computers, some having a measurement technology of 20 or more years ago, have a difficult time to fully implement sophisticated signal processing.  For most, the originating digital signal processing technology that does not allow for sophisticated pulse integrity checks, at least not to the full "Level A" specifications laid down in ISO 6551.

Most flow computer products are able to produce some sort of "Level B" implementation, which partly solves the measuring challenge.  However, solutions with a full implementation of the highest level of signal error compensation, referred to as "Level A" pulse compensation are indeed hard to find.

Flow-X signal processing

Flow-X utilizes the most modern hardware components such as high speed microprocessors and Field Programmable Gate Arrays, a true Level A implementation is available now. This means that all fault signal conditions and pulse disturbances as defined in the ISO6551 standard are correctly recognized and corrected for.

The dual pulse input of a Flow-X module compares at real-time, the digital signals from a dual pulse meter input with a frequency of not less than 10MHz. The Flow-X digtal hardware and software algorithms analyze, at 10MHz speed, in real-time the signal disturbances and compensates subsequently for added, missing, simultaneous pulses and indicate real meter problems.

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