What flow meters are available that can output pulse signals?

Mass flow meters can output pulse signals

Generally, pulses are used only when high measurement accuracy is required, as the error caused by pulse loss is much smaller than the error resulting from fluctuations in the 4-20mA signal. Even so, mass flow meters used for material transfer or trade settlement in devices still employ the 4-20mA signal. Many selection guides for mass flow meters offer both pulse and current output options, allowing for the use of pulse output; however, it has never been used in practice. I think this is mainly because people don’t want to use a dedicated IO card just for this special signal type. Moreover, according to error analysis, even if pulse measurement is used, the overall system error doesn’t change significantly. In short, instruments of the metering grade can ensure accuracy within 0.2% or even 0.1%; at that level they are usually already at their maximum capacity. As for other instruments, depending on their respective measurement principles, even the use of pulse-type technologies does not bring about any significant improvement. . .

Some turbine flowmeters have a pulse signal as their original signal, and some positive displacement flowmeters can also have their original signal designed as a pulse output. For most smart flowmeters, in addition to being able to output an analog signal, they can also generate a pulse signal for measurement through analog-to-digital conversion; even some two-wire flowmeters can produce pulse signals via special electrical wiring arrangements.

Electromagnetic flow meter, ultrasonic flow meter