Jim Mimlitz, SCADAmetrics

When totalizing the total accumulated flow through a non-absolute-encoder flow meter, it is generally preferable to interface with a pulse-per-volume signal (eg. 1 pulse per gallon). However, certain flow meters only offer a 4-20mA signal that is proportional to rate-of-flow. Examples include certain Parshall Flume-Type Wastewater Flow Meters, Differential-Pressure Flow Meters, WH Power Meters, and many others.

While it is certainly possible to program a computer or PLC to perform a running time integral of the rate-of-flow signal, this technique is difficult, time-consuming, and fraught with pitfalls. A straightforward and elegant hardware-based solution is to convert the 4-20mA signal to a pulse, and utilize the EtherMeter’s sophisticated pulse-processing capabilities to provide both totalization and rate-of-flow.

Interested in learning more about this technique? Check out our new Application Note in the Documentation Library: App Note #20

For reference, here is a link to the Brochure for the EtherMeter, which can process pulse signals into total consumption and rate data available in Modbus and/or Allen Bradley automation protocols.

The recommended Milliamp-to-Pulse Converter is Model No. APD-7500-SS-D.  Alternatively, the Octal-Plug Version may be used, Model No. API-7500-SS-D.  For reference, here is a link to the Brochure for the Milliamp-to-Pulse converter: the Model APD 7500 SS D

Accumulating Flow Totals From a 4-20mA Flow-Rate Signal.

Accumulating Flow Totals From a 4-20mA Flow-Rate Signal.

About Jim Mimlitz

Licensed Professional Electrical Engineer @ SCADAmetrics. Specialties: Connecting Flow Meters with SCADA, Telemetry, and Building Automation Systems. Electronic Circuit Design, Software Development.

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