Elementary Analysis of Display Instrument Features of Turbine Flowmeter

Turbine flow meters are flow meters that use a turbine for measurement. The turbine flowmeter first converts the flow rate to the speed of the turbine, and then converts the speed into an electrical signal that is proportional to the flow rate. Level Transmitters, Input Level Transmitters, and Static Pressure Level Transmitters These flow meters are used to detect instantaneous flow and total integrated flow. The output signal is frequency and easy to digitize. In the figure, the induction coil and the permanent magnet are fixed together on the housing. When the ferromagnetic turbine blade passes the magnet, the magnetic resistance of the magnetic circuit changes, thereby generating an inductive signal. The signal is amplified and shaped by an amplifier and sent to a counter or frequency meter to show the total integrated flow. At the same time, the pulse frequency is frequency-voltage converted to indicate instantaneous flow. The speed of the impeller is proportional to the flow rate, and the number of revolutions of the impeller is proportional to the total amount of flow. The output of the turbine flowmeter is a frequency-modulated signal, which not only improves the immunity of the detection circuit, but also simplifies the flow detection system. Its range ratio is up to 10:1 and its accuracy is within ±0.2%. The time constant of the small inertia and small size turbine flowmeter can reach 0.01 second.

The task of the display instrument of the turbine flow meter is to convert the number of output pulses per unit time and the total number of output pulses into instantaneous flow and total flow meters and display them.

The pulse signal output by the preamplifier is irregular in amplitude and waveform. After entering the display instrument, it must first be shaped into a regular rectangular electric pulse signal with a certain amplitude by the shaping circuit, and then pass the frequency/ Current conversion circuit, the frequency signal into the corresponding current signal (4 ~ 20mA) and then convert the instantaneous flow meter value, the total conversion and integration circuit obtained. Some display instruments are displayed locally, and some send DCS displays.