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Flow Measurement Transducers: Core Electronic Raw Pulse Generator Sub-Systems

Quick Answer

For batch control, custody transfer, or totalizer integration, the raw pulse generator sub-system inside a flow measurement transducer is often more useful than the analog output. This sub-system provides a direct frequency signal proportional to actual flow volume. Silver Instruments supplies raw pulse generator options across electromagnetic, Coriolis, oval gear, vortex, and ultrasonic flow meters.

Raw Pulse Generator Basics in Flow Measurement Transducers

Most flow measurement transducers produce more than a 4-20 mA signal. The core electronic sub-system converts a mechanical motion, acoustic phase shift, or induced voltage into a continuous square wave. Each pulse equals a defined volume or mass increment. For example, an oval gear meter may generate 254 pulses per liter while a vortex meter may generate 12 pulses per liter depending on the DN size and bluff body geometry.

In practice, engineers care about pulse resolution, pulse width, duty cycle, and the difference between raw and scaled signals. Raw pulse output sends the full frequency from the sensing element. Scaled output passes through a divider to give one pulse per unit. Raw pulse keeps more resolution for flow computers and high speed counters.

Why Raw Pulse Output Matters for Batching and Total Flow

Imagine a paint manufacturer in Vietnam dosing solvent into a mixing tank. A 4-20 mA loop may drift by 0.5 percent over temperature. A raw pulse signal does not drift in the same way. Each edge or state change is a discrete volume count. The PLC high speed counter adds the pulses and stops the valve at the exact batch volume.

We have seen this on customer sites many times. A desalination plant in Saudi Arabia used an electromagnetic flowmeter with raw pulse output to control antiscalant dosing. The meter signal went to a local totalizer and a PLC counter. The raw pulse resolution allowed the dosing pump to turn on and off within 2 liters of target.

Here is the thing, raw pulse signals are digital, so they reject most analog noise. But cable routing still matters. Keep pulse cables away from VFD motor leads. Use shielded twisted pair for runs beyond 50 meters.

Silver Instruments Pulse Generator Options by Flow Meter Type

Silver Instruments offers raw pulse generator sub-systems across multiple flow technologies. The electromagnetic flowmeter series covers DN15 to DN300 with configurable pulse per unit, frequency output, and 4-20 mA HART as a backup. This works for raw water, wastewater, chemicals, and seawater desalination feed lines.

The oval gear positive displacement flowmeter provides high resolution raw pulse output for diesel, fuel oil, and chemical injection. This meter type is common for DN4 to DN80 lines and low flow batching. The vortex flowmeter gives a linear raw pulse signal from the shedder bar and suits steam, compressed air, and hot water. The Coriolis mass flowmeter can output raw mass pulse, volume pulse, and 4-20 mA simultaneously. This helps a food and beverage plant in Thailand that wants mass total and volume total on the same process line.

The ultrasonic flowmeter and thermal mass flowmeter also support pulse output for clean water, cooling water, or gas monitoring. Most models from Silver Instruments allow field selection of pulse divider, pulse width, and active or passive output by the local keypad or Modbus. If the process temperature swings more than 20 °C, confirm whether the meter includes a PT100 compensation input.

Electrical Parameters You Need to Specify

Do not assume a raw pulse signal will match your PLC input. Check the pulse amplitude first. Common options are 5 VDC, 12 VDC, and 24 VDC. Some meters use open collector NPN or PNP. Others use a relay or active push pull driver. The high speed counter