Ultrasonic level gauge common faults and solutions

The first kind: there will be agitation in the on-site container, and the liquid fluctuation is relatively large, which will affect the measurement of ultrasonic level gauge.

Failure phenomenon: no signal or severe fluctuation of data.

The reason: when ultrasonic level gauges measure distances of several meters, they refer to calm water.For example, the ultrasonic level gauge with a measuring range of 5 meters generally means that the maximum distance to measure the calm water surface is 5 meters, which will be 6 meters out of the factory.When there is agitation in the container, the water is not calm and the reflected signal is reduced to less than half of the normal signal.

Solutions:

1. If the ultrasonic level meter with a larger range is chosen, if the actual range is 5 meters, then the ultrasonic level meter with 10 meters or 15 meters shall be used for measurement.

2. If the ultrasonic level gauge is not changed, and the liquid in the tank is non-viscous, you can also install the wave guide tube, the ultrasonic level gauge probe is placed in the wave guide tube to measure the level gauge height, because the liquid level in the wave guide tube is basically stable.

3. It is suggested to change the two-wire ultrasonic level gauge to the four-wire system.

The second type: foam on the surface of the liquid.

Failure: the ultrasonic level gauge is always searching, or will display "lost wave" status.

Reason: foam is able to absorb ultrasonic wave obviously, caused echo signal to be very weak.Therefore, when more than 40-50% of the surface area of the liquid is covered with foam, the ultrasonic level meter will be absorbed most of the signals, resulting in the level meter can not receive reflected signals.This has nothing to do with the thickness of the foam, mainly with the area covered by the foam.

Solutions:

1. Install the wave guide tube, put the probe of the ultrasonic level gauge in the wave guide tube to measure the height of the level gauge, because the foam in the wave guide tube will reduce a lot.

2. Replace it with a radar level gauge to measure. The radar level gauge can penetrate any foam within 5 cm.

The third;The high temperature in the pool or tank will affect the ultrasonic level measurement.

Fault phenomenon: it can be measured when the water surface is close to the probe, but not when the water surface is far away from the probe.When the water temperature is low, ultrasonic level gauge measurement is normal, the water temperature is high ultrasonic level gauge measurement.

Reason: liquid medium under 30 to 40 ℃ general won't produce steam and fog, more than the temperature would be easy to produce steam or fog, the launch of the ultrasonic wave in the firing process of ultrasonic level meter through the steam will decay time, returned from the liquid surface reflection attenuation will again, finally return to probe ultrasonic signal is very weak, so the measurement is less than.And below this kind of environment, the probe of ultrasonic level gauge is easy to form water bead, water bead can block the transmission of ultrasonic wave and receive.

Solutions:

1. To increase the range, in fact, the height of the tank is 3 meters, to choose between 6 meters to 9 meters ultrasonic level meter.Can reduce or reduce the effect of steam or fog on the measurement.

2. The probe should be made of polytetrafluoroethylene or PVDF and made into a physical seal, so that it is not easy to condense water droplets on the transmitting surface of the probe.As for the emission surface of other materials, water droplets are relatively easy to condense.

The fourth kind: there is electromagnetic interference on site.

Failure phenomenon: ultrasonic level meter data is irregular jump, or simply show no signal.

Reason: there are many motors, frequency converters and welders in the industrial field that will affect the measurement of ultrasonic level gauge.The electromagnetic interference will exceed the echo signal received by the probe.

Solutions:

1. Ultrasonic level gauge must be reliably grounded. After grounding, some interference on the circuit board will run away through the ground wire.And this grounding is to be a separate grounding, can not share the same ground with other equipment.

2. The power supply cannot be the same as the inverter and motor, nor can it be directly induced from the power supply of the power system.

3. The installation site shall be far away from frequency converter, frequency conversion motor and high-power electric equipment.If you can't get away from it, you have to put a metal meter box on the outside of the level meter to isolate the shield. This meter box also needs to be grounded.

The fifth: enter the blind zone

Failure: full range or arbitrary data.

Reason: ultrasonic level gauge will have blind area, generally within 5 meters of the measuring range, blind area is 0.3-0.4 meters.The range within 10 meters is 0.4-0.5 meters.After entering blind area, ultrasonic wave can appear arbitrary value, cannot work normally.

Solution: 1. During installation, the height of the blind area should be considered. After installation, the distance between the probe and water level should be greater than the blind area.