Typical Faults and Troubleshooting Methods in the Spectrophotometer

As a precision instrument, the spectrophotometer will inevitably undergo some changes in its technical condition due to various reasons such as working environment and operating methods during the operation process, which may affect the performance equipment and even induce equipment failures. and crashes. Therefore, analysts should understand the basic principles and instructions of the spectrophotometer, and be able to detect and eliminate these hidden dangers in time, and repair the faults that occurred in time to ensure the normal operation of the equipment.

1) If the test wavelength is changed greatly, wait for a while and recalibrate the \"0\" and \"100%\" points after the lamp heat balances. Then measure again.

2) When the needle instrument is not energized, the needle of the ammeter should be on the zero scale. If it\'s not the cas, perform a mechanical zero adjustment.

3) After using the bowl, please rinse it with distilled water immediately, and wipe the water with a soft, clean gauze to prevent the surface finish from being damaged and affecting the light transmission of the cuvette.

4) The operator should not easily move the bulb and the light reflector, so as not to affect the luminous efficiency.

5) 1900 type spectrophotometer, because its photoelectric receiving device is a photomultiplier tube, its own characteristic is large magnification, so it can be used to detect weak photoelectric signals, but not to detect strong photoelectric signals. Light. Otherwise, signal drift will easily occur and sensitivity will decrease. Given its aforementioned characteristics, care should be taken not to expose the photomultiplier tube to light in a prelongated maintenance and use of this type of instrument. Therefore, when preheating, you should open the lid of the cuvette or use a light blocking rod to prevent prolonged exposure to light. Performance drift leads to unstable work.

6) RearIf the sensitivity of the amplifier is off, it must be reset.

7) Cuvette compatibility. The cuvette must be used together, otherwise the test results will be meaningless. A comparison must be made before each test. The specific method is as follows: inject the same solution into the two cups to be tested respectively, and place the instrument at a certain wavelength. Quartz cuvettes; Distilled water 220 nm and 700 nm, glass cuvettes: Adjust the transmission of one cell to 100%, measure the transmission of the other cells and record the difference between the indicated values ​​and the direction of ttransmission of light. If the transmission difference is within the range of ±0.5%, it can be used together. If it exceeds this range, its impact on test results should be considered.

Several typical faults that may occur in the operation of the spectrophotometer and their troubleshooting methods:

1) The instrument cannot be zeroed. Possible reasons:

a)The light door cannot be fully closed. Solution: Fix the light barrier assembly so that it closes completely.

b) The \"100%\" transmission is facing down. Solution: Readjust the \"100%\" button.

c) The instrument is very humid. Solution: Open the photocell cassette, blow it with a hair dryer for a while to dry it, and replace the desiccant.

d) Circuit failure. Solution: Send to repair department to overhaul circuit.

2) The instrument cannot be set to \"100%\". Possible reasons:

a) The light energy is not sufficient. Solution: Increase the sensitivity magnification speed or replace the light source lamp (although the lamp is still on).

b) The cuvette rack is not in place. Solution: Adjust the cell holder to drop it.

c) The photoelectric conversion part is getting old. Solution: Replace the part.

d) Circuit failure. Solution: adjust the circuit.

3) During the measurement process, the \"100%\" point often changes. Possible reasons:

a) The position of the cuvette in the cuvette holder is inconsistent or there are liquid droplets on the surface. Solution: Wipe the surface of the cuvette with a lens cloth, then place it on the left side of the cuvette and position it with a positioning clip.

b) Circuit failure (voltage, photoelectric receiverric, amplifier circuit). Solution: Send for repair.

4) The digital display is unstable. Possible reasons:

a) Warm-up time is not sufficient. Solution: Extend the warm-up time to about 30 minutes (due to aging and other reasons, some instruments will also work unstably when in working status for a long time).

b) The desiccant in the photocell breaks down, which makes the micro-current amplifier wet. Solution: Bake out the circuit and replace or bake out the desiccant.

c) Excessive environmental vibration, high air velocity near the light source, strong external light, etc. Solution: Improve the working environment.

d) Photocells, circuits and other reasons. Solution: Send for repair.

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