The Contrec Model 515 (Application GN01) is the frequency input version of the 515 natural gas flow computer, built to take a pulse or frequency signal straight off a turbine or PD meter. It accepts dual-channel quadrature pulse inputs, so it can check the two pulse trains against each other to ISO 6551 Level B pulse security – useful if anyone ever questions whether the pulse count has been tampered with or corrupted along the way.
Gas compressibility and density are calculated using the AGA-8 Detailed Characterization Method across gas mixtures of up to 21 components, using live temperature and pressure inputs, and gross heating value is worked out to ISO 6976 and GPA 2172-96. This is the same calculation basis used for fiscal and custody transfer gas metering, so it’s suitable for billing-grade applications on gas distribution or power generation balancing points, not just internal monitoring.
In actual application, this application code is normally paired with a turbine or PD meter that already outputs a pulse signal, with the 515 handling all the compressibility correction and heating value math downstream. It has an onboard adjustable transducer excitation supply so you can power the field transmitters directly, plus 4-20mA retransmission and dual RS-232/RS-485 Modbus RTU ports so it talks to most SCADA or DCS systems without extra conversion gear. It also keeps a built-in log of totals, averages, and alarms, so you have an audit trail if anyone questions the readings later.
Before we quote this, we would normally check the meter’s pulse output type (single or dual channel), the gas composition (for the AGA-8 calculation), the temperature and pressure input ranges, and what output signals your control system needs. Hope this helps.
