Spectrophotometer FAQ and Processing

(1) Turn on the power

Open the benefit board of the sample room, the pointer of the ammeter is left or right, and the zero position cannot be adjusted with the zero adjustment potentiometer knob.

① Check that the voltage of the light source front lamp should be 11.5V ± 0.5V (adjustable 100% knob), clockwise, and turn it to the end.

② On the left side of the instrument, remove the rectangular cover plate, there is a coarse adjustment zero potentiometer, the rotation of the J1 degree time meter makes the meter point to the right (100%), and the counterclockwise adjustment is the opposite.

③Check whether the internal connection wires of the instrument are disconnected, weak soldered, poorly connected, etc., including seven-core brackets and brackets.

④Whether the amplifier is damp or seriously damp, which will affect the zero adjustment. In order to get rid of the moisture quickly, you can use a hot air blower to blow hot air into the dark area of ​​the photoelectric tube, but be careful not to be too hot and not to affect the plastic silicone base.

It is generally required that when the zero position is adjusted, when changing from 1st gear to 3rd gear, the difference in the change of the ammeter pointer should be within 10% of the ammeter reading.

Faults in the micro-current amplifier and damage to the photocell may also cause the zero position to be adjusted. You can remove the cassette and remove the two lead wires of the photocell. Test the amplifier alone to determine whether it is caused by a photoelectric cell problem. If the amplifier is damaged, connect it to the amplifier to repair it.

(2) Turn on the power

The light source is on, the zero adjustment potentiometer is adjusted normally, and no monochromatic light passes through the sample chamber.

Turn the wavelength indicator to the left of 580nm, turn the 100% adjustment knob clockwise to make the light source the brightest, and place a white paper vertically on the right wall of the sample chamber for easy observation.

① Open the back panel, you can directly observe whether the position of the light source lamp is good, carefully loosen the two fastening screws, adjust the parts of the lamp holder, and observe whether there is a light spot on the paper at the same time, first adjust the light spot to the brightest and most complete, and then Tighten the screws. If there is a slight change, you can slightly turn the lamp holder to make the light spot better.

② After careful adjustment, if there is still no light report, check the optical path of the monochromator. Make the instrument horizontal and vertical, remove the difference plate of the monochromator, and you can see the internal junction of the monochromator. Where there is light entering, the light source bulb and the position of the lamp can be moved to make the incoming light the brightest. Use a piece of paper to move the light spot to the direction of the collimating mirror, so that the light spot falls on the center of the collimating mirror. If it is too left or too right, adjust the angle of the reflector in the adjustable optical system according to the method introduced in the manual (the up and down adjustment is fixed at the factory, and the up and down direction of the light spot is realized by adjusting the inclination angle of the reflected light appropriately.

The parallel light from the collimating mirror shoots to the shuttle mirror, returns to the collimating mirror after being dispersed, and gathers on the focal plane of the exit slit through the collimating mirror, and a bright light band can be seen, which means there must be monochromatic light. The light is emitted from the exit slit, and the monochromatic light in the sample chamber passes to the receiving photocell.

If the spectral band is not at the exit slit, it is too high, too low, too left or too right to emit monochromatic light from the exit slit, adjust the 3 pins of the collimating mirror, if the wavelength reading disc is placed at 11180nm, it will be at The exit slit should be shading, and the adjustment range is generally small. If the change is large, it may be that some part or medium or nail is loose. In this way, we must pay attention to the fault in this aspect, and adjust it after careful troubleshooting and recovery.

(3) Connect to a suitable power supply

The indicator light is on, but the light source light is off.

① Check whether the voltage regulator circuit board of the front lamp is enclosed in the socket, check whether the output of the power transformer (17V~) and the filament of the bulb are broken.

②Check that the voltage at two points at the contact end of the lamp should be 11.5±0.4V (100% adjustment, clockwise to the end).

③ If there is no 11.5V output voltage, check the rectifier tube according to the general rules, and the DC voltage of the capacitor is about 20V.

④ Check the voltage-stabilizing printed circuit board, whether there is any falling off, false soldering or component damage, and then check the solder joints of each connecting line.

⑤ Check and repair according to the circuit diagram of the regulated power supply in the manual.

(4) Each adjustment knob can work

But the electric meter indication swings from side to side and is unstable.

The unstable pointer is related to the following aspects: unstable light source; light leakage, damp, loose structure, etc.; micro-current amplifier performance deterioration; photoelectric tube failure.

①Input the AC voltage of 190-240V, check the voltage stability of the output 11.5V, and require the output change to be less than 0.005v. Check with a 5-digit digital voltmeter. If there is no such setting, you can observe that the output ripple coefficient (with a vacuum tube millivolt meter) is <3mV, and there is no beating phenomenon.

②Use a black cloth to build the right side of the instrument, the test room, the photocell cassette part, etc. one by one, observe whether the indication of the electric meter is affected, check out the light leakage parts, and eliminate them.

Open the test room, adjust the "0" position in front of the light gate (the light hole on the right side of the test room) and place an opaque light shield to observe whether the 0" position changes. If there is any change, it means that the light gate has light leakage and needs to be disassembled Repair the colorimetric part and check the light gate parts. When the lever is not pressed down, the light gate baffle should cover all the light holes, so when the lever is lowered, the light gate should be fully opened.

The instrument should be placed on a flat platform, so that the bottom of the instrument is stable, and the meter pointer should be stable without external force.

③The lake inside the photocell cassette causes the amplifier to be unstable and the pointer of the meter to vibrate. When the sensitivity is adjusted from level 1 to level 3, the zero position of the meter will deviate greatly, and it will not be around the zero position (referring to the zero position adjustment) , At this time, it is necessary to replace the inner magnetic glue of the male gel, and keep the dark area dry. When the micro-current amplifier 3Df6F deteriorates the core performance of the field effect tube and reduces the impedance, it is necessary to replace it with a core 10ua 3DJ6F FET.

First observe whether the amplifier is moving when the photocell is not installed. If the pointer of the ammeter is unstable when the photocell is illuminated, and the light source is good, then there is something wrong with the photocell.

(5) The use of matting film 0, 5A, 1, 1.5A

The above extinction films are called neutral light transition films, because the transmittance of these light transition films in a wide range of wavelengths is basically the same.

When the concentration of the measured solution is too concentrated and the A value is too high, for example, the measured value is 1.7A, we will easily cause the reading on the electric meter indication.

Error, if a 1A sugar light film is placed at the reference solution during the measurement, the meter reading is 0.74A, and the actual value is 1.74A.

In addition, it needs to be added that the 1A of the so-called 1A filter is a nominal value, and the actual value is about 1A. The actual value measured under the actual use of the length should prevail. For example, the measured value is 0.95A, and the meter reading in the above example is 0.74A, then the actual value is 0.74A + 0.95A=1.69A, and so on.

(6) The use of the five levels of sensitivity range

The sensitivity range is divided into five levels, which can change the load resistance and feedback resistance of the current amplifier, so that the same input signal current, the voltage drop on the load resistance varies with the resistance, and the output signal strength is different. The load resistance is small, and the output signal is small, that is, the deflection of the meter pointer is small. This has an advantage, and its stability is relatively good. Therefore, in principle, try to start from the sensitivity level 1. When the adjustment is 100%, adjust it clockwise to the maximum, that is, the bulb voltage is the maximum, and the light intensity is the maximum, and the sensitivity is still not adjusted to 100% (A0). To 2, if it is not enough, the third gear can be used and so on.

(7) Use praseodymium and neodymium filters to correct the wavelength

PrNd filter is a kind of glass product containing rare metal praseodymium and neodymium, its spectral absorption characteristics are fixed.

It is mainly used to correct the wavelength accuracy of the instrument. Because its absorption peak has a standard value, it can be used to verify the accuracy of the instrument wavelength. It is used as a basis for adjusting the length of the instrument. Now it is recommended to use the 529nrn absorption peak.

①Indicate the wavelength plate at 580nm first, and the emitted monochromatic light should be the first color. If it is not the first color, adjust the wavelength screw to make the emitted light be the first color.

②The point-by-point test method can be used to record the light rate of the wavelength and the corresponding wavelength. Because the thickness and composition of each piece of wrong glass are different, its light transmittance is also different, but its absorption peak is unchanged. .