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Keison PFP7 Скачать руководство пользователя страница 34

33

PFP7/REV C/01-08

8.5

Signal processing description

Refer to

Figures 8.5.1

and

8.5.2

.

The signal from the PIN (PD1) diode is amplified by IC1, a high input impedance op-amp. The
coarse gain control switches 1, 10 and 100 Megohm resistors into the feedback to change the
gain  on  the  first  three  ranges.  On  range  4  the  100  Megohm  resistor  is  left  in  circuit  and  the
sensitivity  of  the  7107(IC5)  is  increased  by  a  factor  of  approximately  10.  The  10  Kilohm
potentiometer feeding into the inverting input of IC1 is a factory preset control for compensating
for any dark current from the PIN diode and for any offset in IC1. The output of IC1 is then fed
through a filter network consisting of R8, C4 and R9, C5; the signal is then fed into IC2 a non-
inverting buffer with RV2 its preset offset adjustment.

The  front  panel

blank

potentiometer, RV3, provides an adjustable DC offset which is fed into

the inverting input of IC3 to compensate for any signal from the flame background when setting
the readout to zero with the flame alight.

The front panel

fine

sensitivity potentiometer, RV4, controls the gain of IC3 and the values in

the  feedback  of  this  stage  are  selected  to  enable  the  sensitivity  to  be  varied  continuously
between each of the switched steps of the coarse sensitivity control.

The output of IC3 is fed via a filter consisting of R15 and C7 to the 7107 (IC5). The 7107 is an
Analogue  to  Digital  converter  complete  with  a  7  segment  decoder/driver  for  the  3½  digit  LED
display. The sensitivity of the A to D converter is set by RV6 to approximately 1mV per digit on
coarse sensitivity ranges 1, 2 and 3 and 0.1mV per digit on coarse sensitivity range 4 by SW1B
and RV7. The output of IC3 is also fed to the non inverting buffer IC4 (with preset offset control
RV5) to give a buffered recorder output of 1mV per digit on ranges 1, 2 and 3 and 0.1mV per
digit  on  range  4.  The  preferred  decimal  point  may  be  selected  by  SW2  which  connects  the
relevant decimal point to 0V through a 560 ohm resistor, R16, R17 or R18.

Figure 8.5.1

: Main circuit board layout.

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Содержание PFP7

Страница 1: ...Flame Photometer Models PFP7 and PFP7 C Operating and Service Manual...

Страница 2: ...d only be removed by personnel who have been trained to avoid the risk of shock At this point the unit must be disconnected from all services i e gas and electric 4 References should always be made to...

Страница 3: ...1 Calibration standards 11 3 2 Sample preparation 12 3 3 Dilution 13 SECTION 4 14 Operation 14 4 1 Front and rear panel controls 14 4 2 Operation 16 4 3 Calibration PFP7 17 4 4 Calibration PFP7 C 19...

Страница 4: ...tem description 28 8 2 Combustion and ignition system description 29 8 3 Optical system description 30 8 4 Power supply description 30 8 5 Signal processing description 33 Component replacement 35 9 1...

Страница 5: ...able atomic flame emissions of the alkali and alkaline earth metals in terms of the emission wavelength and the colour produced Element Emission Wavelength nm Flame Colour Sodium Na 589 Yellow Potassi...

Страница 6: ...eristic wavelengths are easily isolated from those of most other elements due to wide spectral separation The analysis of Na K Li Ba and Ca are typically determined at low temperatures i e 1500 2000 C...

Страница 7: ...of 3ppm Na and K and 5ppm Li are set to read 100 Specificity Interference from Na K and Li when equal in concentration to the test element will be less than 0 5 Stability Better than 2 over 5 minutes...

Страница 8: ...refer to Section 2 5 2 1 4 Drain The instrument will need to be sited near a drain or sink to enable disposal of waste liquid A suitable receptacle can be utilised if provision is made for easy dispo...

Страница 9: ...rictor 5 fitted into the end of the fuel inlet 6 on the mixing chamber The restrictor should remain in place if butane propane or L P G is to be used as fuel Keep the restrictor screw in case of any f...

Страница 10: ...of heat Fit the air and fuel inlet connectors to the ports provided on the rear of the instrument 1 Fit the appropriate lengths of tubing to the connectors 12 and 13 and secure with the screw clips pr...

Страница 11: ...nised water Check that no air bubbles are trapped in this tube and that it flows and runs to waste freely Ensure that the drain trap is pushed completely down on its clip 2 5 Accessories Always use re...

Страница 12: ...rds encompass the expected range of the sample concentrations 3 Standards should be prepared so as to ensure that the region in which measurements are made coincide with the concentrations that produc...

Страница 13: ...rom direct sunlight in a cool place ideally at temperatures below 25 C Glass containers should not be used for storage as they can affect the sodium concentration levels Standards should be stored in...

Страница 14: ...mples using deionised water or suitable extractants e g saturated CaSO4 for sodium in soil Extraction is more successful using a blender macerator or shaking machine If the sample is organic then the...

Страница 15: ...unit thereby causing fuel ignition d p This switch controls the position of the decimal point fuel A fine needle valve that controls the flow of fuel and enables optimum flame conditions to be set bla...

Страница 16: ...PFP7 Both FS1 and FS2 should be of an anti surge type POWER IN A three pin receptacle for the AC mains supply POWER OUT Two three pin sockets for flame photometer accessories such as a compressor and...

Страница 17: ...before continuing Depress the ignition switch for a further 20 seconds This process may be repeated until successful ignition occurs If the fuel valve has to be opened more than 5 turns more than rec...

Страница 18: ...centration by cross reference to the curve A calibration curve is prepared using standard solutions containing known concentrations of the elements to be determined and if necessary other materials to...

Страница 19: ...maining standard solutions if used to construct the calibration curve and note the results 4 When the blank and standards are set unknown samples can be aspirated and the results noted either directly...

Страница 20: ...djust the fuel valve in a clockwise direction until a peak reading is obtained Re set the display reading accordingly for the standard being aspirated NOTE There is a time delay between adjusting the...

Страница 21: ...e environments A bactericidal agent should be used when cleaning parts during routine maintenance 4 7 Good practice guidelines 1 It is most important that the nebuliser mixing chamber and burner are k...

Страница 22: ...1 4 Maximum operating pressure 100psi 100psi Working temperature range 5 to 80 C with no freezing 5 to 80 C with no freezing Nominal filtration rating 5 m 5 m Bowl material Polycarbonate Polycarbonat...

Страница 23: ...ght kg 4 5 4 Datalogger The analogue RS232 datalogger is an easy to use PC based data acquisition product that plugs into the serial port of a PC desktop or laptop and requires no power supply Replaci...

Страница 24: ...rrect no further action is required 4 If the consumption rate is too low this is likely to be caused by a blockage in the fine capillary tubes and can usually be cleared by passing the cleaning wire t...

Страница 25: ...isconnect the mixing chamber from the chimney unit by unscrewing the knurled locking ring and dropping the chamber clear of the chimney 4 Remove the fluted burner from the top of the burner tube 5 Rin...

Страница 26: ...set for the element being determined refer to Section 4 2 Operation Fuel cylinder nearly empty Replace cylinder with a fully charged one Instrument in strong draught Relocate the instrument Instrumen...

Страница 27: ...refer to Section 4 2 Instrument not draining adequately Ensure the U tube is clear of blockages and that the drain trap is at the correct level 7 5 Flame will not light Possible cause Solution Drain U...

Страница 28: ...Re make standard Nebuliser completely blocked Check the nebuliser performance as defined in Section 6 2 Weekly maintenance 7 8 Unable to set blank Possible cause Solution Blank contaminated Re make t...

Страница 29: ...and is factory set and sealed The aspirated sample is passed into the mixing chamber where the fuel gas is introduced The sample aerosol then strikes the PTFE impact bead which further breaks up any l...

Страница 30: ...ed by lifting the yellow locking ring and rotating the knob on the side of the regulator until the correct pressure is shown on the pressure gauge From the air regulator the air passes to the nebulise...

Страница 31: ...the transformer primary winding the other side of which is connected to the neutral from the power switch The transformer primary is auto wound to provide a step up function to supply 240V for the ig...

Страница 32: ...he reference level set by RV8 is factory set for optimum switching of the solenoid on off Adjustment of this may have a significant impact on the safe operation of the flame photometer and should only...

Страница 33: ...32 PFP7 REV C 01 08 Figure 8 4 2 Power supply and flame failure detection circuit...

Страница 34: ...nsate for any signal from the flame background when setting the readout to zero with the flame alight The front panel fine sensitivity potentiometer RV4 controls the gain of IC3 and the values in the...

Страница 35: ...34 PFP7 REV C 01 08 Figure 8 5 2 Main circuit board...

Страница 36: ...crewed and the mixing chamber 7 lowered from the chimney and removed 4 The burner 8 can be withdrawn from the burner tube 9 and the end cap removed by releasing the three socket head screws 10 The imp...

Страница 37: ...through the top of the back plate The chimney back plate can now be removed taking care not to strain the thermocouple cable The stainless steel inner chimney can now be pivoted up and cleaned with a...

Страница 38: ...unit Remove the four screws on the cover plate to release the filter wheel assembly from the chimney assembly Remove the two grub screws from the filter wheel to gain access to the filters 3 To fit a...

Страница 39: ...38 PFP7 REV C 01 08 Figure 9 1 3 Filter wheel and filters 1 filter wheel 2 PIN diode PCB mounting bracket 1 2 1 2...

Страница 40: ...the retaining screws 2 Identify the power supply PCB mounted on the base of the unit Note the orientation and polarization of the two multiway connectors branching from the cableform Disconnect these...

Страница 41: ...e top rear cover as described in Section 9 2 step 1 Disconnect the three connectors from the back of the main PCB by pulling on the housing box do not pull on the cables Note the orientation and polar...

Страница 42: ...solenoid replacement Refer to Figure 9 2 1 1 Ensure that power fuel and air supplies to the instrument are disconnected Remove the top rear cover as described in Section 9 2 step 1 2 Identify the two...

Страница 43: ...the large knob from the fuel needle valve on the front panel by loosening the two grub screws and then fully close the valve taking care not to over tighten and remove the preset stop knob by looseni...

Страница 44: ...he nylon tube to the outlet of the air regulator assembly Pull the tube and compression fitting out of the air regulator assembly 3 Remove the nut on the rear panel air inlet bulkhead connector The ai...

Страница 45: ...7 segment display red Qty 2 012 004 Rocker switch illuminated green 017 024 Rocker switch bias 1w 017 025 Display driver ICL7107 Qty 2 019 002 Thermocouple assembly 027 023 Allen key 2 5AF 060 037 Adj...

Страница 46: ...g the details below UK Office Keison Products P O Box 2124 Chelmsford Essex CM1 3UP England Tel 44 0 330 088 0560 Fax 44 0 1245 808399 Email sales keison co uk Please note Product designs and specific...

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