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How did you troubleshoot various faults of the potentiostat?
Date: 2022-04-06Read: 0
What is a potentiostat?
The potentiostat itself is a branch under a rectifier, with constant potential and constant current functions.
Constant potential refers to using the reference electrode feedback as a constant standard to control the output of the organizer.
It's simple. For example, for a newly built pipeline with a cathodic protection potential requirement of -1.2V, the constant potential meter is set at -1.2V. In order to meet the requirement of -1.2V, the constant potential meter increases its output until the potential reaches -1.2V. At this point, the output voltage is, for example, 10V, and the current is, for example, 5A. Therefore, we can say that this pipeline meets the protection requirements with a required voltage of 10V and a required current of 5A
The cathodic protection system includes auxiliary anode facilities, cathode facilities, and constant potential meters. These three parts are independent of each other and are an organism. When one of them fails, the instrument cannot work normally. Therefore, the constant potential meter can be regarded as the window of the cathodic protection system, through which system symptoms can be observed and treated accordingly.
（2） Several common faults and their solutions
(1) When the potentiostat malfunctions, the instrument knob can be turned to "self-test" for testing. If it is normal, it indicates that the potentiostat is working properly, and the fault may be in the on-site area. If there is a backup instrument, it can also be switched to another testing machine. If the other one is also not normal, it indicates a fault on site. Otherwise, the fault is in the on-site area Constant potential meter.
(2) The constant potential meter has two working modes: manual and automatic. When it is determined that the constant potential meter is faulty, the working mode knob of the instrument can be turned to "manual" for testing. The "manual" adjustment can output current and voltage, indicating that the main circuit, voltage regulator, and trigger circuit are working normally. The fault is in the automatic part.
(3) When the fault of the constant potential meter is determined to be in the automatic part, the alarm current limiting integrated block can be removed for testing. If the instrument resumes operation, it indicates that there is a fault in the alarm and current limiting parts, and can be plugged back into the integrated block separately. When the instrument is not working properly in which integrated block it is plugged into, it can be determined that there is a fault in this part.
(4) If the alarm and current limiting circuits are removed and the instrument still does not work properly, the fault may be in the comparator and impedance conversion circuit, which can be tested separately using good integrated blocks.
(5) When the constant potential meter is turned on to the "manual" working mode, it cannot work. You can first check whether the fuses are intact, whether the digital meter displays normally, and whether the voltage of each group of the stabilized power supply is working properly. When checking the trigger circuit, you can first use a good trigger board to test the machine. When it is determined that the trigger board is faulty, then test each level of components for damage in sequence (for synchronous integrated blocks, good integrated blocks can be directly compared).
(6) If all control boards are normal, the fault may be in the main circuit. It can be checked whether the voltage passing through the transformer is normal, and whether the diodes and thyristors in the entire circuit have been broken down, causing an open circuit or short circuit. .
(7) When the constant potential meter is normal through the above tests, it indicates a fault on site. The anode facility, cathode facility, and reference electrode can be checked in sequence. The anode facility consists of an anode cable, an anode rod, and a ground bed (in pipeline cathodic protection, the vertical distance between the anode ground bed and the pipeline is usually required to be short of 300m). When the anode cable is disconnected or the anode grounding resistance reaches a constant value, the output voltage of the potentiostat increases and the output current becomes zero.