The magnetic flap level gauge can directly reflect the actual state of the liquid level in the tank without using other means. This simple, clear, stable and intuitive measurement benefit has been increasingly recognized by more and more users. In the actual manufacturing process of instruments, manufacturers can also expand the functions of liquid level gauges by adding some additional technical means, so that they can be applied to practical production control. The measurement accuracy of a large range magnetic flap level gauge over 2 meters is usually comparable to that of a differential pressure transmitter, and therefore it is increasingly valued by users. However, due to the inconsistency between the environment and usage conditions of the measurement site and the environment verified by the manufacturer, some even differ greatly, resulting in the incomplete realization of the maintenance free benefits marked by many manufacturers, and the demand for testing also increases accordingly.

The magnetic flap level gauge is developed based on the principle of buoyancy and magnetic coupling. When the liquid level in the tested container rises or falls, the magnetic float in the liquid level gauge body tube also rises or falls accordingly. The long-lasting magnetic steel inside the float is transmitted to the magnetic flip column indicator through magnetic coupling, driving the red and white flip columns to flip, thereby achieving clear indication of the liquid level. By opening and closing the built-in reed switch contacts, current or voltage signals can be transmitted. Magnetic flap level gauges are usually calibrated through simulation methods (not specified in this method specification) at the factory to ensure that they match the actual medium when supplied.

Specific on-site calibration steps for level gauges:

Firstly, it is necessary to determine the density of the measured medium

The medium density can be measured using a standard density meter, and the magnetic flap level gauge can also be retrieved based on specific information provided by the user. The medium density needs to be recorded and filed to ensure that it meets the requirements of the level gauge user manual. Although theoretically the density of the medium has an impact on the reading of the liquid level gauge, in practical use, the zero and full values of the liquid level gauge can be directly adjusted through a potentiometer.

Secondly, it is necessary to determine the reference zero point

(1) Measure the inner diameter D of the connecting pipeline with a vernier caliper, and use a magnetic flap level gauge to determine the lower point of a standard liquid level on the upper part of the tank. If possible, it can be polished into a groove to prevent the depth gauge from swinging and marked;

(2) Manually inject water into the storage tank without pressure. Stop injecting water when the water level is slightly higher than the inlet pipe of the level gauge. Open the manual ball valve E at the lower connecting flange of the magnetic flap level gauge and loosen the connecting flange F between the tank body and the calibrated level gauge (do not remove it to prevent water flow from surging) until there is no surging flow in the pipeline. Close E and remove the flange. When the liquid in the tank is stable, open E and wait for it to drip for 1 minute (if necessary, drain the water through the drainage valve to improve detection efficiency);

(3) The magnetic flap level gauge measures the distance ha from the measuring point to the water surface using a depth gauge steel tape. The actual zero position height h0=ha-D/2, which is the measurement zero point of the level gauge.

3. Calibration of each liquid level point

(1) Install the flange, close E, and continue to inject water into the tank until the main scale indicating the level to be calibrated is reached. After the water surface stabilizes, measure the output current Ii and the water level height hi. The actual liquid level is H0=h0 hi=ha - D/2- hi;

(2) Continue measuring other points until full range is reached.

4. Calibration of liquid level zero and full degree

At the same time as determining the reference zero point, adjust the zero potentiometer so that the output electrical signal is displayed as 4mA; adjust the full-scale to the upper limit of the standard liquid level, increase the full-scale potentiometer so that the output electrical signal is displayed as 20mA. If there is a deviation in the output during the measurement of the lower stroke of the magnetic flap level gauge, refer to this method for adjustment. On site calibration requires repeating the above steps for three return measurements.