Cuptor DO308

Service manualMETTLER TOLEDOAnalytical

Business location Schwerzenbach: Address Sonnenbergstrasse 74 (Industrie Vieri), 8603 Schwerzenbach, Switzerland Telephone +41 44 806 77 11 Telefax +41 44 806 73 50 Internet www.mt.com

Edition: September 2005

© Mettler-Toledo GmbH 2005ME-51710384 Printed in Switzerland 0509/8.12 Drying oven

DO308P51710384

Service Manual ME-51710384 08/2005

DO308 Overview

ContentsA-General 1

1. Introduction 32. Safety measures 33. Exploded view drawings 64. Spare parts 95. Tools 96. Circuit description 107. Specifications 12

B-Checks 131. Maintenance 15

C-Troubleshooting 171. Measuring points 192. Troubleshooting list 193. Error messages 20

D-Repairs 211. Repairs 232. Temperature adjustment 27

E-Document history 29

F-Data section 31

Service Manual ME-51710384 09/2005 A-1

DO308 General

Contents1. Introduction 3

2. Safety measures 3

3. Exploded view drawings 63.1 Control unit 63.2 Sample tube 73.3 Heating part 8

4. Spare parts 9

5. Tools 9

6. Circuit description 106.1 Temperature control 106.2 CPU tasks 11

7. Specifications 12

A-General


DO308 General


DO308 General

1. IntroductionThe METTLER TOLEDO DO308 Drying Oven is used for moisture determination by the Karl Fischer method for samples where direct moisture determination is not possible. Examples are insoluble samples or those whose determination yield false results due to side reactions with the KF reagent. The oven can also be an alternative to external extraction. The drying oven can be used together with both the volumetric and coulometric METTLER TOLEDO Karl Fischer titrators.

The sample in a glass boat, or in an aluminium foil insert, is slid into a glass tube, where it is heated. This heating drives off any moisture from the sample in the form of vapor, which is then fed from the heated glass tube to the KF titration cell by a stream of dry purge gas, such as dry air or nitrogen.

2. Safety measuresThe DO308 has been tested for the experiments and intended purposes documented in these operating instructions. However, this does not absolve you from the responsibility of performing your own tests of the product supplied by us regarding its suitability for the methods and purposes you intend to use it for. You should therefore observe the following safety measures.

Measures for your protection- Never place or install objects on or above the apparatus! These could catch fire.- Avoid heat buildup above the apparatus by leaving a free space of approx. 1 meter! Readily flammable materials

could ignite.- For safety reasons, there must be at least 30 cm between the wall or other equipment and the rear and sides of

the device! No containers, chemicals or other devices should be placed behind the device!

- Never touch the guard of the oven as well as the flange of the sample inlet which is attached to the flange ring of the heating tube during or after operation! You could burn yourself.

Risk of fire

Risk of burns


DO308 General

- Before the instrument is opened, the power cable must be disconnected from the external power supply.- Install the power cable so that it doesn't come into contact with the hot parts of the oven! Otherwise the cable

could melt and cause a lethal technical fault.- Ensure that you plug the power cable supplied into a receptacle outlet that is grounded! In the absence of ground-

ing, a technical fault could be lethal.- Switch the apparatus off and disconnect the power cable before you change blown fuses! An electric shock could

be lethal.

- Never work in an environment subject to explosion hazards! The housing of the apparatus is not gas tight (explo-sion hazard due to spark formation, corrosion caused by the ingress of gases).

- Never use a reactive gas as a purge gas! It could lead to an explosion.- In the determination of water contents of organic substances and when using ambient air as purge gas, ensure

that no explosive gas mixtures can be formed! Risk of explosion!- Check the gas paths and drying tubes for free gas flow! This prevents buildup of an overpressure in the titration

cell, which could lead to an explosion.- Open the stop cock before you stop the gas flow, switch off the apparatus or lower the temperature! This prevents

siphoning back of the titration solution into the hot drying oven. Failure to do this could result in an explosion hazard.

- Don't use flammable liquids with a flashpoint below 325 °C in conjunction with the oven DO308! Otherwise they could catch fire.

- Use flammable liquids only in quantities, too small to cause spread of fire!

- When using chemicals and solvents, comply with the instructions of the producer and the general lab safety rules!- When working with chemicals or solvents of unknown composition, it is the operator's responsibility to obtain in-

formation from appopriate sources about possible hazards associated with the use of such chemicals or solvents!- The drying oven DO308 has been designed and built as a laboratory device. It is only intended to be used to drive

out water from a small amount of sample at temperatures from room temperature up to 300 °C. Using the device for any purpose other than that stated above, or using it in any application that does not correspond to the techni-cal data, is considered to be improper usage. Any damage resulting from such use is the sole responsibility of the operator!

Risk of an electrical shock

Risk of explosion

Risk of burns

Caution


DO308 General

Measures for operational safety- Only those parts or assemblies specified in the spare parts list may be replaced.- The service technician must be familiar with the “Safety instructions for contractors” issued by the company using

the instrument.- Use only fuses of the type specified in the Operating Instructions!- Exclude the following environmental influences: • powerful vibrations, • direct sunlight, • atmospheric humidity greater than 75%, • temperatures below 5 °C and above 40 °C, • powerful electric or magnetic fields!

Caution


DO308 General

3. Exploded view drawings

3.1 Control unit� � � � �

� �

��


DO308 General

3.2 Sample tube

�

��


DO308 General

3.3 Heating part

��

15

16

17

18

19


DO308 General

4. Spare parts

Item Description Used in Part No. Remarks1 Coversheet DO308 513712042 Lid DO308 513712093 Knob DO308 513712174 Power Supply DO308 513712115 Power line filter DO308 513712126 Control PCB DO308 513712197 Power switch DO308 513712088 Sample tube DO308/DO307 513712069 Slider DO308/DO307 5137110310 Screw cap DO308/DO307 5119112911 PTFE ring 5137121512 Heating tube DO308/DO307 5110620113 Insulating inserts DO308/DO307 5137121314 Jacket tube DO308/DO307 5137121415 Stop cock valve DO308/DO307 5119113016 Flow meter 51191131 For gas drying unit17 Gas inlet DL39 DL39 5110866918 Gas inlet DL38 DL38 10509119 Guide rod DO308/DO307 51371101

5. Tools

Item Description Part No. Remarks1 Calibration Set 511062092 Adapter cable 51371216 To connect the calibration temperature sensor to the

DO3083 Screwdriver Torx 10 511916594 Screwdriver Torx 20 51191660


DO308 General

6. Circuit description

6.1 Temperature controlThe heating unit is controlled according to the set temperature. The temperature on the heating unit is controlled by the internal sensor B1. The heating power is activated from the micro controller via IC D1 and the selection 120/230V from the SSR V12.If the heating unit is overheated for some reason (i.e. defective Solide state relais), the relay K1 will open and interrupt the heating. (Error 03) This information is stored in the EEPROM and K1 will stay open until the instrument is switched off and the problem is solved!

The temperature limiter circuitry and/or the overtemperature circuitry works as following:

- The maximal temperature measurement for the overtemperature circuitry will be activated only if measured over 310°C.

- The relative temperature measurement for the overtemperature circuitry will be activated if:1. the temperature is rising more then +2 °C/sec. over the set temperature, even if the temperature potentiometer

is set to 0 during operation!2. the difference of the actual slope is >0.11 °C for 6 sec. to the actual Interval of 6-12 sec.

That means not only the SSR could be defective, but also following parts have to be checked:

- Heating tube and/or temperature sensor Pt1000- Electronic circuitry (PCB)- Electromagnetic interference‘s- Temperature calibration

The heating unit is identical for 120 V and 230 V. At 230 V mains supply, the heating unit is controlled to about <50% power supply. The instrument can be calibrated automatically with a calibration temperature sensor, which can be connected to X5. (see section D)


DO308 General

6.2 CPU tasksPower interruptionIf a power interruption less then 50ms occurs, the actual status of operation is not interrupted!If a power interruption more the 50ms occurs, the watchdog circuitry is taken over, see below!

WatchdogThe program is producing continuous pulses, which are checked by a small electronic circuitry.As soon as the program is disturbed or interrupted, the electronic releases a reset impulse!

Control of heatingThe heating output of the heating unit will be constant, even if there are power fluctuations!The micro controller is measuring the power voltage indirectly from the input ‘AdHeatCurrent’and adjusts the heating output if any power fluctuation is occurring.

If any voltage measurements on the heating unit are done, please consider above points!

EEPROMFollowing values are stored in the EEPROM:

- calibration valuepower control heating unit:- nominal value- actual value- heat reset- if a power interruption less then 50 ms occurs, the actual status of operation is stored (see also under power

interruption)


DO308 General

7. Specifications

Power supply connectionVoltage 100 - 230 VACAdmissible voltage fluctuations ±10%Frequency 50/60 HzPower consumption 450 WFuses T 3.15A L 250V

TemperatureControl range 40 °C ... 300 °CMeasurement deviation ±5 °C in the middle of the sample tube at 300 °C

Interface5-pin mini Din socket for air pump box 24 VDC regulated, max. 10 W

DimensionsFootprint housing width 256 mm, depth 180 mmDimensions width 300 mm, height 300 mm, depth 550 mmSample tube diameter 30 mm, lengt 390 mmEffective boat volume 15 cm3

Weight 9.1 kgAmbient conditions

Ambient temperature 5…40 °Cmax. relative humidity (not condensing) 80% for temperatures up to 30 °C, linear decreasing up to 50% relative

humidity at 40 °CUse indoorsHeight up to 2000 m Installation-/ Overvoltage category IIPollution degree 2

MaterialsHousing Sheet steelSample tube, heating tube, jacket tube Borosilicate glassFlanged rings AluminumGas carrying tubing PolyamideSample boat Borosilicate glass

Service Manual ME-51710384 09/2005 B-13

DO308 Checks

Contents1. Maintenance 15

1.1 Visual inspection/cleaning 151.2 Cleaning the sample tube 151.3 Changing the silica gel and molecular sieves 151.4 Software version 151.5 Checking the temperature 15

B-Checks


DO308 Checks


DO308 Checks

1. Maintenance

1.1 Visual inspection/cleaningThe housing of the oven is not splashwater-proof. In case of contamination, it can be cleaned with a cloth moistened with alcohol.

1.2 Cleaning the sample tubeYou can clean the sample tube with chromic acid or other glass cleaning agents.

- To dismantle it, proceed as described in section D.- Dry the tube before installation and bake out (Described in the operating instructions).

1.3 Changing the silica gel and molecular sieves- You should change the silica gel of the gas drying unit as soon as it starts to turn pink.- You should change the molecular sieves when the drift value of the titration solution is two to three times higher

than that with fresh molecular sieves.

1.4 Software versionThe software version is displayed when switching on the instrument, i.e. Version 01.03.

1.5 Checking the temperature- Check if the internal temperature sensor lies flat on the heating tube.- Remove the sample tube from the furnace and replace it by the aluminum temperature sensor holder of the adjust-

ment set (see section D).- Insert a certified thermometer approx. 120 mm into the heating tube.- Set temperature to 100 °C. LCD heating on, after approx. 10 min. starts flashing, after another 5 min. thermometer

should show oven temp. 100 °C ± 10 °C.- Set temperature to 200 °C. LCD heating on, after approx. 10 min. starts flashing, after another 5 min. thermometer

should show oven temp. 200°C ± 10°C.

NoteIf temperature difference to the set temperature is more than ± 10°C and/or if temperature difference to the display is more then ± 10°C, new calibration will be necessary. (See section D)

Maintenance check list

Model: D

O308 _________________________ D

ate: _____________________________

Serial number: _________________________

Software version: ___________________

Signature: ____________________________

Visual checks

Components

Check Cleaning

OK

Power cable

• •

❏

On/O

ff switch

•

❏

Connector sockets •

❏

Loose screws

•

❏

Housing

• •

❏

Coversheet •

•

❏

Knob •

•

❏

Tubing connections •

•

❏

Sample tube

• •

❏

Stop cock •

❏

Slider •

❏

Air pump

•

❏

Technical checkout

Components

Check Cleaning

Adjust OK

Light in power sw

itch •

❏

Software version

•

❏

LCD display

•

❏

Temperature check 100 °C

•

•

❏

Temperature check 200 °C

•

•

❏

Set temperature [°C]

Disp. temperature [°C]

Ext. thermom

eter [°C]Difference [°C]

Limits of error [°C]

10010

20010

Service Manual ME-51710384 09/2005 C-17

DO308 Troubleshooting

Contents1. Measuring points 19

2. Troubleshooting list 19

3. Error messages 20

C-Troubleshooting





1. Measuring points

Description Test points ValuePower supply black/red wires 24 V DC ± 1 VHeater Plug X4 40 – 60 ΩPT1000 Plug X8 approx 1.1 kΩ at ambient temperature

2. Troubleshooting list

Malfunction Possible cause RemedyDO308 not working at all Mains power missing

24 VDC missingPower switch defectiveF1/2 (3,15 AT) in Power line filter defective

Check mainsReplace power supplyReplace mains switchReplace F1/2

Heating not OK H1 heating unit defectiveH1 connections corrodedPT1000 internal wiring looseSSR V12 defectivePulse SSR from IC 8 missing

Replace heating tubeReplace heating tubeCheck wiring or PT1000Replace PCBReplace PCB



3. Error messagesThe Error Messages are shown on the display. To remedy cause of error:switch of DO308, correct cause of error and switch DO308 on again!

Error Nr. Error text Meaning RemedyE01 ERR_SENS1_CUT1 Internal temperature sensor open. - Check PT1000.

- Replace Control PCB.E02 ERR_SENS1_SHORT2 Internal temperature sensor B1 short circuit. - Check PT1000.

- Replace Control PCB.E03 ERR_SENS1_OVERT3 Temperature limiter circuitry is activated

(Overtemperature).- Check PT1000.- Replace Control PCB.

E04 ERR_SENS1_CALIB4 Calibration of the instrument not OK. - Check PT1000.- Replace Control PCB.- New calibration necessary.

E05 ERR_SENS2_CUT5 External temperature sensor B2 open (only if B2 connected).

- Check external PT1000 Adjustment temperature sensor.

E06 ERR_SENS2_SHORT6 External temperature sensor B2 short circuit (only if B2 connected).


E07 ERR_SENS2_OVERT7 Temperature limiter circuitry is activated (Overtemperature).


- Replace Control PCB.E08 ERR_SENS2_CALIB8 Calibration of the instrument not OK (only if

B2 connected).- Check external PT1000 Adjustment

temperature sensor.- Replace Control PCB.- New calibration necessary.

E09 ERR_HEATING9 Oven not heating. - Check heater.- Check PT1000.- Replace Control PCB.

E10 ERR_OPT10 Opto coupler defective. - Replace Control PCB.E30 ERR_OVEN30 Calibration of the instrument not OK (no cali-

bration).- New calibration necessary.

Service Manual ME-51710384 08/2005 D-21

DO308 Repairs

Contents1. Repairs 23

1.1 Opening the control unit 231.2 Replacing the Control PCB 231.3 Replacing the power supply 231.4 Replacing the power line filter 231.5 Replacing the sample tube 241.6 Replacing the heating tube 251.6.1 Removing cable connections 251.6.2 Disassembling of the heating tube 251.6.3 Assembling of the heating tube 261.6.4 Restore cable connections 26

2. Temperature adjustment 272.1 Preparing the adjustment 272.2 Starting the adjustment 27

D-Repairs


DO308 Repairs


DO308 Repairs

1. Repairs

1.1 Opening the control unit- Open the control unit by removing the 2 torx screws on the bottom and the 2 torx screws at the back of the control

unit.- Lift up the front panel.

1.2 Replacing the control PCB- Lift off the cover of the knob, hold it, loosen the nut and remove it.- Open the instrument. See "1.1 Opening the control unit".- Unplug all connectors from the control PCB.- Unscrew the 4 nuts holding the PCB wit a 5.5 mm tube wrench.- Carefully remove the PCB, taking care to the glass, which is located between the LCD display and the cover (see

drawing).- Reassembly is carried out in the reverse order.

1.3 Replacing the power supply- Open the instrument. See "1.1 Opening the control unit".- Unplug all connectors from the power supply.- Remove the PCB.- Reassembly is carried out in the reverse order.

1.4 Replacing the power line filter- Open the instrument. See "1.1 Opening the control unit".- Unplug all connectors from the power line filter.- Remove the 2 torx screws from the back and remove the power line filter.- Reassembly is carried out in the reverse order.


DO308 Repairs

1.5 Replacing the sample tube- Switch off the DO308, disconnect the power cable and let the oven cool down.- Unscrew the screw cap (a) and remove the sample transport assembly (guide rod and

glass boat).- Disconnect all tubing from the sample tube.- Unscrew the two screws on the holder (b) with the provided screwdriver and remove the

spacing plate (i).- Remove the holder from the guide rods (e) and take it away from the sample tube.- Remove the slider (h) from the square bar (g).- Unscrew the two screws from the sample tube fixing (c) in the middle of the flanged ring

(f).- Carefully pull the sample tube, together with the sample tube fixing (c) and the gasket

(d), out of the oven. - Push the gasket on the new sample tube and place the sample tube fixing between the

upper gas outlet and the thickening of the sample tube, as shown in the picture above. (Take care, that the counter sinkings for the screws have to point frontwards.)

- Carefully slide the sample tube into the oven, with the guide rods sliding to the lower holes of the sample tube fixing.

- Tighten the sample tube fixing.Do not tighten the screws too tightly!- Reinstall the slider to the square bar.- Slide the holder from above on the sample tube and attach it to the guide rods.- Attach the spacing plate to the square bar and fix it on the holder with the two screws.Do not tighten the screws too tightly!- Insert the sample transport assembly and reconnect the tubing.

�

�

� ��

�

�

�

�


DO308 Repairs

1.6 Replacing the heating tubeBefore disassembly of the heating tube is carried out, the sample tube must be removed (see "1.5 Replacing the sample tube"). After that, the control unit must be opened (see "1.1 Opening the control unit").

1.6.1 Removing cable connections- Press the small orange levers on the plug X4 using a small screwdriver and pull out the heater cables from the

plug.- Press the small orange levers on the plug X8 using a small screwdriver and pull out the PT1000 cables from the

plug.- Unplug the grounding wire leading to the tube.- Press on the grey bushing and pull the tube out of it.- Pull the cables out of the control unit. 1.6.2 Disassembling of the heating tubeIf the heating tube is not defective, then wear clean gloves for avoiding finger prints.- Unscrew the 3 torx screws and remove flange in order to have access to the 4

torx screws holding the heating.- Carefully remove the 4 torx screws, holding the touch guard (o).- Remove the touch gard (o).- Remove the jacket tube (n).- Remove insulating inserts (m).- Undo cable clip at the cable bushing.- Holding the heating tube, carefully pull the 4 cables out of the bushing/tube.

Note- Also replace insulating ring (m) if damaged.- Any fingerprints on the heating tube (l) must be removed with a cloth and a little

alcohol!

�

�

�

�

�

�


DO308 Repairs

1.6.3 Assembling of the heating tubeWear clean gloves.- Use insulating tape for holding together the 4 cables.- Holding the heating tube, carefully push the cables trough the bushing/tube.- Fasten the cable clip at the cable bushing.- Check if the plastic insulation (k) is correctly placed.- Place the insulating inserts (m) and slide in the jacket tube (n).- Reinstall the touch guard (o) observing the correct adjustment.

Note- Also replace insulating ring (m) if damaged.- Any fingerprints on the heating tube (l) must be removed with a cloth and a little

alcohol!

1.6.4 Restore cable connections- Push the cables and tube trough the opening of the control unit.- Press on the grey bushing and push the tube in place.- Plug in the grounding wire.- Check new heating tube for resistance and isolation. - Measure resistance between the cable connections of the heater (40 – 60 Ω). - Measure resistance between one connection of the heater to the ground of the housing (> 100 MΩ).- Press the small orange levers on the plug X8 using a small screwdriver and push the PT1000 cables into the

plug.- Press the small orange levers on the plug X4 using a small screwdriver and push the heater cables into the plug.

Note- It is necessary to carry out a temperature adjustment. See "2. Temperature adjustment".

�

�

�

�

�

�


DO308 Repairs

2. Temperature adjustment

2.1 Preparing the adjustmentTools needed for the temperature adjustment: Calibration set ME-51106209.

The adjustment temperature sensor is officially calibrated and supplied with a certificate from the manufacturer valid for one year. Recertification is possible at every official certifing body.

- Switch power off and disconnect the power cable.- Dismantle the sample tube (see "1.5 Replacing the sample tube") and install the temperature sensor holder in the

mounting flange of the sample tube. Fix it with the knurled screw.- Insert the temperature sensor through the hole into the heating tube. Connect the temperature sensor with its cable

to the ADJUSTMENT mini-DIN socket of the control unit.

Note- It is important to perform the adjustment at a constant room temperature, away from sunlight and ventilation

systems.- The adjustment procedure only works correctly if the internal temperature in the heating tube T1 is < 50 °C and

the calibration temperature sensor T2 < 80 °C when starting.

2.2 Starting the adjustment- Switch on the instrument.

Ready for Calibration

Setpoint: 0°CAct. Value ext.: 25°CAct. Value int.: 26°C

- Press Start when the following display appears.

> T2> T1

Calibration at 100 °CCalibration is running

set point: 100°Cact. value ext.: 48°Cact. Value int.: 54°C

1. step. - in 10 min. heating up to 100 °C, controlling with T12. step. - stabilising and calibration with T2 (max. 90 min.)


DO308 Repairs

Calibration at 250° CCalibration is running

set point: 250°Cact. value ext.: 128°Cact. Value int.: 144°C

1. step. - in 10 min. heating up to 250 °C, controlling with T12. step. - stabilising and calibration with T2 (max. 90 min.)

228°C230V

Man 0:00:00 OffT2

The calibration will be ended and stored after the 2. step (250 °C), if the actual temperature on calibration sensor T2 is within ± 5 °C to the nominal value.

After a successful calibration, the values are stored, and the display will change to the information screen, although for the temperature display the external sensor (T2) is in use. It is now possible to enter a temperature and start heating whereby the temperatue in the oven can be observed.

NoteIf above conditions are not met, the calibration will be interrupted and an Error Message will be displayed!

Service Manual ME-51710384 09/2005 E-29

DO308 Document history

E-Document historyIs my service manual really up to date?• Service manuals are constantly updated.• All changes are listed in the Register E.• The status of the document is defined by the date of issue (front page and footers of manual) and by the index,

e.g. ME-51710xxxC. The first version has no letter.• Visit our website at: www.mtanainfo.com to download actual versions of service manuals.

Document history Index Date of issue

First issue of the Service Manual DO308 - September 2005 (09/2005)

Service Manual ME-51710384 09/2005 E-30

DO308 Document history

Service Manual ME-51710384 09/2005 F-31

DO308 Data section

ContentsWiring diagramm 33

F-Data section


DO308 Data section


DO308 Data section

METTLER TOLEDO reserves all rights in this document and in the subject thereof. By ac-ceptance of the document the recipient acknowledges these rights and undertakes not to publish the document nor the subject thereof in full or in part nor to make them available to any third party without METTLER TOLEDOs prior express written authorisation nor to use it for any purpose other than for which it was delivered to him.

Wiring diagram

m

��

��

��

��

��

��

��

�

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

�

��

��

��

��

��

��

��

��


DO308 Data section

Cuptor DO308

Documents

sample tube

heating tube

following safety measures

burnsservice manual

heated glass tube

safety measuresthe do308

safety reasons

2do308 generalservice