The electric contact level gauge is designed based on the different electrical resistivity of water and steam. The electrode of the measuring cylinder has a low impedance to the cylinder in water. The impedance of the cylinder is high in the steam.
As the water level changes, the number of electrodes in the water also changes. Convert into a change in resistance value. Transmit to the secondary instrument to achieve functions such as water level display, alarm, protection interlock, etc.

Troubleshooting of electric contact level gauge:
1. The electrode of the electric contact level gauge is prone to being covered by oxides, and over time, its reliability and sensitivity gradually decrease. This can be solved by reducing the electrode point current, as this greatly reduces the adsorption force of the electrode.
Sharp pointed electrodes are also acceptable, as they have a certain self-cleaning ability, which extends the service life of the electrode and increases the reliability of the work.
In addition, the method of inclined installation can also be accepted to reduce the chance of simultaneous alarms at the upper and lower limits of the electrode, as this may reduce the probability of the electrode droplets communicating with the droplets flowing down from the container wall.
The electric contact level gauge should be frequently drained and flushed with steam to reduce the coverage on the electrode contacts, keep the contacts clean, and prevent the indicator light of the secondary meter from dimming or misindicating.

2. The upper and lower limit alarm devices of the electric contact level gauge sometimes act simultaneously when there is a special conflict, that is, the upper and lower limit alarm indicators of the secondary gauge of the electric contact level gauge flash simultaneously.
Although it is impossible for the actual liquid level heights at both high and low ends to exist simultaneously, this phenomenon often occurs on the secondary gauge, especially when the liquid level detection cylinder is just discharged and the gauge is reopened, it is more likely to appear.
When the on-site glass level gauge indicates 60% of the scale, the secondary level indicator light in the control room flashes at both 50% below the lower limit and 75% above the upper limit, indicating that the liquid level is both above and below the upper limit. Obviously, this is impossible.
The reason for this is as follows: just after the liquid level detection cylinder is discharged, the actual glass level gauge reading is below the upper limit (75%) mark, but at this time, the high alarm indicator light flashes, indicating that the high alarm circuit has formed a path.
This may be due to a short circuit in the electrode or a disconnection of the external wiring of the electrode, which is in contact with the shell of the detection cylinder (power common terminal), causing the indicator light to flash; It may also be caused by dirt on the outer end of the electrode and a short circuit with the outer shell of the detection cylinder; It is also possible that the circuit cable has a grounding phenomenon.
Sometimes this high alarm indicator light flashes for a few special minutes and then disappears on its own, returning to normal. This indicates that the high alarm flash is due to the residual liquid droplets on the electrode during discharge communicating with the liquid droplets flowing down the wall of the detection cylinder container, causing false indication.
If the high alarm indicator light still flashes after half an hour and the actual liquid level is normal again, then the above reasons should be followed for investigation. This high alarm flashing phenomenon is sometimes caused by false liquid level.
Sometimes, when the liquid level is at normal level, the liquid level detection cylinder flashes an alarm at the lower limit 5% mark after being discharged, indicating that the circuit has been broken. This may cause the external terminal of the electrode to be disconnected or poorly contacted during discharge, and the cable lead to be disconnected. This is caused by poor contact of the wiring terminal at the control point of the racetrack in the circuit; It may also be a problem with the circuit of the lower limit (50%) of the secondary meter. Sometimes false liquid levels can also cause low alarm flashes.

1. State adjustment method
Generally speaking, before the fault is determined, do not touch the components in the circuit casually, especially adjustable devices such as potentiometers. However, if multiple reference measures are implemented in advance (such as marking the position or measuring voltage or resistance values before triggering), triggering is still allowed if necessary. Perhaps sometimes the malfunction can be resolved after the modification.

2. Isolation law
The fault isolation method does not require comparison of equipment or spare parts of the same model, and is safe and reliable. According to the fault detection flow chart, segmentation and encirclement gradually narrow the fault search range, and then with signal comparison, component exchange and other methods, the fault will generally be found quickly.

3. Capacitor bypass method
When a circuit produces strange phenomena, such as display disorder, the capacitor bypass method can be used to determine the approximate faulty circuit part. Connect the capacitor across the power and ground terminals of the IC; Connect the transistor circuit across the base input or collector output to observe the impact on the fault phenomenon. If the capacitor bypass input terminal is invalid and the fault phenomenon disappears when bypassing its output terminal, it is determined that the fault is manifested in this stage of the circuit.

4. Observe opinions
Utilize visual, olfactory, and tactile senses. Sometimes, damaged components may discolor, bubble, or show burnt spots; Burned components will produce some special odors; Short circuited chips will heat up; Virtual welding or detachment can also be observed with the naked eye.

5. Discharge method
The so-called elimination method is a method of determining the cause of faults by plugging and unplugging some plug-in boards and components inside the machine. When the instrument returns to normal after removing a certain plug-in board or component, it indicates that the fault occurred there.

6. Tapping hand pressure method
It is common to encounter the phenomenon of instruments running intermittently, which is mostly caused by poor contact or virtual soldering. For this situation, it is acceptable to use tapping and hand pressure methods
The so-called "tapping" refers to gently tapping the plug-in board or component with a small rubber mallet or other tapping object on the possible faulty part to see if it will cause errors or shutdown faults. The so-called 'manual pressure' refers to the process of turning off the power and then manually pressing down on the plugged components, plugs, and sockets when a fault appears, and then turning on the machine to see if the fault can be resolved. If it is found that knocking the casing once is normal, and then knocking it again is not normal, all the connectors should be re inserted firmly and tried again. If it is troublesome and unsuccessful, another method can only be found.

7. Heating and cooling method
Sometimes, when the instrument works for a long time or when the working environment temperature is high in summer, it will show a fault. After shutting down and checking, it will be normal. After a period of shutdown and restarting, it will be normal again. After a while, the fault will appear again. This phenomenon is caused by poor performance of individual ICs or components, and the high-temperature characteristic parameters cannot meet the requirements of the indicators. To identify the cause of the malfunction, the temperature rise and fall method is acceptable.
The so-called cooling refers to using cotton fibers to wipe anhydrous alcohol on the possible faulty parts when the fault appears, so as to cool it down and check whether the fault is eliminated. The so-called temperature rise refers to artificially raising the ambient temperature, such as placing an electric soldering iron close to the suspicious area (be careful not to raise the temperature too high and damage normal components) to see if the fault appears.

8. Substitution method
Require two instruments of the same model or sufficient spare parts. Replace a good spare part with the same component on the faulty machine and see if the fault is resolved.

9. Shoulder riding technique
The shoulder riding method is also known as the parallel method. Place a good IC chip on top of the chip to be inspected, or connect good components (resistors, capacitors, diodes, transistors, etc.) in parallel with the components to be inspected, maintaining good contact. If the fault is caused by an open circuit or poor contact inside the device, accept this method to troubleshoot.

10. Comparison method of magnetic flap level gauge
Two instruments of the same model are required, and one of them is operating normally. Necessary equipment such as multimeters and oscilloscopes are also required to use this method. According to the nature of comparison, there are voltage comparison, waveform comparison, and static impedance comparison
Output result comparison, current comparison, etc. The practical method is to run the faulty instrument and the normal instrument in a sympathetic manner, then detect the signals at some points and compare the two sets of signals measured. If there is a difference, it can be concluded that the fault lies here. This method requires maintenance and repair personnel to have considerable knowledge and skills.
Common troubleshooting of magnetic flap level gauge
Magnetic flap level gauges often experience malfunctions in practical applications, and the causes of these malfunctions are diverse. Some are caused by single component failures, while others are caused by multiple component failures occurring simultaneously.
Below, the common faults and their causes of magnetic flap level gauges in application are analyzed as follows:
Fault 1: Local display is normal and remote transmission is abnormal. Reason analysis:
Generally speaking, there are multiple reasons for this type of malfunction, and the following are the more common ones:
1. Resistance virtual soldering.
2. The pressure exceeds the rated value, causing damage to the switch.
3. Domestic glass tube reed switches are fragile and prone to short circuits or open circuits, resulting in abnormal long-distance transmission.
4. When the medium temperature is too high, the metal sheet expands due to heat, and the metal contact gap of the reed switch is small, which makes it easy to show a closed state.
Fault 2: Both the remote transmission and the magnetic flap do not move. This fault phenomenon is usually caused by abnormal float, and the following symptoms are important:
The reasons for the damage of the float in the magnetic flap level gauge due to incorrect indication on the display panel are usually as follows:
1. Due to incorrect strength design of the float, it sinks inward and becomes deflated when subjected to pressure.
2. The welding joint is not fully penetrated or missed, causing the weld seam to crack when the float is under pressure, and the float will be flooded.
3. The float cannot be used normally due to demagnetization caused by prolonged use or long-term use at high temperatures.
4. Due to the loosening of the magnetic steel in the float, the float cannot function properly.
Fault 3: Due to the float being stuck, the display panel's indication is inaccurate, causing the float in the magnetic flap level gauge to get stuck. There are several common reasons for this:
1. The ambient temperature is too low, and the float cannot move normally due to the freezing of the medium.
2. The installation angle of the float is less than 87 degrees, and due to the tilt of the float, its up and down movement is affected.
3. The float is stuck and unable to move normally due to its magnetic adsorption of iron filings or other pollutants.
4. Due to poor sealing, the float is trapped by impurities that have infiltrated, preventing it from rising or falling.
The so-called finding the cause of the malfunction only solves half of it. Through the analysis of common faults in the magnetic flap level gauge above, we have basically found a solution to the problem. Based on the identified faults and their causes, we can take targeted measures to address them.