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When troubleshooting, the cause should first be analyzed. The causes and phenomena of device failures are complex.
In order to find out the error, it is necessary to carefully observe, carefully recognize, analyze and compare the error phenomenon.
Because there are many types of instruments, and the structure, circuit and function are very different, to discuss the cause of the error and the troubleshooting method in detail, it is necessary to carry out an analysis of the specific instrument and information Refer to the manufacturer's drawings, instructions, and service manuals for the manufacturer's device circuitry.
Here is a brief discussion of some common and common mistakes from the perspective of correct operator usage and analysis.
(1) Instrument display system error
1. The power indicator does not light up. The cause of the error:
2. The cause of the gauge suddenly fluctuating:
The power supply voltage fluctuates too much and some components in the electronic circuit Sudden damage; contact open or short circuit; High voltage control failure.
(2) Light source system failure
1. Hollow cathode lamp does not light. The cause of the error:
There is a problem with the power supply to the lamp or it is not connected; the contact between the lamp socket and the lamp socket is poor; the connection of the lamp socket is broken; the lamp is leaking.
Examination and treatment method: Check the power supplymaintenance, the wiring and the connections separately. If not a circuit problem, replace the lamp to check.
2. The color of the cathode glow of the lamp is abnormal. The cause of the error: The inert gas in the lamp is impure.
Investigation method: reverse power-on treatment under working current or high current (80mA, 150mA).
3. There is luminescence outside the cathode terminal of the lamp or there is a spark discharge in the cathode. The cause of the error:
The pressure of the inert gas in the lamp decreases and cannot maintain the normal discharge, the latter is caused by oxides or impurities on the cathode surface.
Investigation method: In the former case, replace the lamp with a new one; in the latter case, conduct a current in excess of ten milliamps until the sparking ceases. If invalid, replaceReplace the lamp with a new one.
4. The reason for the tritium lamp failure: The tritium lamp power supply system is faulty; the ignition voltage of the tritium lamp increases due to long-term use; The tritium lamp has expired. Determination method: treat reasons separately.
5. The reason for the tritium lamp power failure is insufficient: the light bar is small; Examination method: increase light barrier; reset light path; Replace lamp with a new one.
(3) Energy output error
1. The hollow cathode lamp is on and there is no energy output after the high voltage is turned on. Cause of error: No negative peak The hollow cathode lamp emits abnormal light or the position is wrong; the wavelength is not correct; the burner blocks the light;
The monochromator is defective; the host circuit is defective. Examination method: DThe second, third and fourth situations are easy to investigate, and the fifth and sixth situations must be dealt with sequentially according to the provisions of the instrument manual or service manual.
2. Reasons for low output power:
The lamp power is low; optical path adjustment is not good; the lens or the optical components in the monochromator are dirty; the wavelength is not allowed; the gain of the amplifier circuit is reduced; the photomultiplier tube ages.
Investigation method: If the energy is generally reduced throughout the band, check whether the photomultiplier tube is aging, and whether the negative high voltage is normal;
If the energy is low, it is related to the wavelength. In addition to checking whether the optical components are dirty, you should also check whether there is a mechanical position change in the monochromator optical system;
If it is due to the confusion of the wavelength display, the wavelength should be recalibrated; If it is a line gain issue, it needs to be investigated further and corrected according to the service manual.
3. The energy display does not change during operation. The cause of the error:
There is a problem with the connection of the preamp before the host circuit; the main amplifier is abnormal.
Examination method: Check the preamp connector and op amp. Adjust the potentiometer according to the service manual requirements.
4. The energy is not zero when the light is blocked. Cause:
The preamp component or main amp component is not properly adjusted or damaged.
Examination method: Use a digital meter to monitor the output of the preamp, adjust the Potentiometer on the circuit board if the light is blocked so the energy reading is zero, or replace the op amp on the main amp.
(4) Error in signal recording
1. The zero point is not correct. Cause of the error: The hollow cathode lamp is aging, the intensity is too weak and the wavelength setting is not accurate. ; quartz window and condenser surface contamination; The sample beam and reference beam of the two-beam instrument do not match.
Examination and treatment method: According to the specific reasons, take appropriate measures. For instruments with automatic withering device, the digital display is not at (0.000 ± 0.002) when the button is pressed. A and the automatic zeroing circuit can be adjusted. Set the set point to zero or use the torch to block the light so the instrument outputs 10mV. If the extDigital readout absorbance is not 1,000, adjust the digital readout set point on the display board circuit to set the absorbance to 1,000.
2. Cause of static baseline drift failure: failure of light source system and detection system.
Examination method: First determine that the instrument is wet. Place the moisture-absorbing silica gel, turn on the instrument to remove moisture, and the instrument's stability will gradually normalize after a period of time. Find out if the instrument's separate ground wire is ok and the instrument's ground wire (connected to the instrument's case) cannot be shared with the neutral wire.
Any electromagnetic induction will cause the instrument to drift. Use an oscilloscope to measure the waveform of the synchronous demodulation control detection pointattitude” and compare it to the standard waveform. If the waveform is abnormal, it should be adjusted to make it normal.
A small change in the synchronous demodulation control waveform can cause the instrument to drift.
The stability of the element lamp and lamp power supply, the stability of the negative high-voltage power supply, etc., may cause baseline drift. If the problem is with the power supply, it should be dealt with according to the service manual.
3. Causes of ignition baseline drift failure: static baseline drift; Atomization system failure.
Methods of investigation and treatment: Exclude static baseline drift; check whether the suction capillary is clogged and forms bubbles, whether the waste liquid drains smoothly and whether water accumulates in the mist chamber.
An iUnstable gas source pressure and insufficient torch preheat can cause drift. Of course, if the wavelength is not set correctly, there will also be drift. They should be treated on a case-by-case basis.
4. Excessive noise and unstable readings Causes of error:
The light source system, nebulization system, spectroscope system and detection system are not working properly.
Method of investigation: First, distinguish whether the fault comes from the atomization system or from the electrical detection system. Comparing the situation of inhaling and spraying “pure water” by igniting and not igniting the flame: This can be judged by the stability of the baseline.
If the fault is determined to be from the atomization system, then further assessment is required as to whether it is from the flame or the sprayer;
You can Spray “pure water” and adjust the sprayerate to see if the noise level is significantly reduced or disappears, otherwise the noise could be mainly from the flame.
You can adjust the combustion ratio, burner height and stable gas source pressure to observe the change in noise level. The atomizer is the main source of noise in the flame atomization system.
If it is determined that the fault is mainly due to the electrical detection system, it is important to distinguish whether it is due to the lamp power supply or the detection system.
Use a qualified copper lamp to fully preheat the instrument and lamp, cut off the human light, and examine the noise level at this time.
If normal, the problem is with the lamp power supply or with the element lamp. Check the lamp power supply further or replace the Lampe with a new one.
If the negative is from the lamp or lamp power supply, further checks of the monochromator system and detection system are required. If the error phenomenon changes with wavelength, it can be assumed that the error mainly comes from the monochromator system.
With two-beam instruments and as the lamp current is increased, the baseline drift increases, indicating that the two beams of the monochromator are mismatched. Stray light inside the monochromator, dust and dirt on the surfaces of the grating and its optics can increase the noise level.
The detection system is one of the main sources of noise. Use a multimeter and an oscilloscope to find out if the fault comes from the power supply or the photomultiplier tube or the linear circuit.
Checking for noise bugs is a difficult oneTask. Sometimes the error phenomenon is the superimposition and synthesis of several parts and factors. from.
Unstable readings indicate that there is a large amount of noise superimposed on the absorbance signal. This is not good for the measurement.
The causes of unstable readings are mainly in the atomization system, suction capillary clogging, atomization nozzle corrosion, waste liquid accumulation in the atomization chamber, and contamination of air and acetylene or the pressure is not good. Stable, the concentration of the test solution matrix is too high, there are precipitates and inclusions;
The burner seam is deposited with carbon and inorganic salts or the seam is clogged, causing the main flame to zigzag. All these situations both affect reading stability. Specific problems should be checked and ruled out.
(5) Limits of sensitivity and detectionzen errors
1. Reasons for sensitivity errors:
The working conditions of the instrument are not optimal; the relative position and concentricity of the capillary and the choke nozzle are not good; the position of the impact ball is not good; Waste liquid accumulates in the nebulization chamber;
Investigation method: According to the method provided in the operation manual and maintenance manual, find out the reasons one by one and improve the treatment.
2. Causes of detection limit deviation error: various errors leading to low sensitivity; various errors that lead to excessive noise and unstable readings.
Investigate and fix the method: Investigate the error fully and fix it with the related methods mentioned above.
