Metrohm 765 User Manual

CH-9101 Herisau/Switzerland
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765 Dosimat

Instructions for Use

8.765.1023

2005.06 ti/dm

Content

Content

1 Overview ...................................................................................................................2

2 Operation with the keyboard ...................................................................................4

2.1 Keypad........................................................................................................................ 4

2.1.1 Key <RATE> .......................................................................................................6

2.2 Modes ......................................................................................................................... 6

2.2.1 Mode DOS, dosing ..............................................................................................7

2.2.2 Mode DIS R, repetitive dispensing....................................................................... 9

2.2.3 Mode DIS C, cumulative dispensing.................................................................... 9

2.2.4 Mode PIP, pipetting............................................................................................ 10

2.2.5 Mode DIL, diluting..............................................................................................11

2.2.6 Mode CNT D, content dispenser .......................................................................12

2.3 User memory ............................................................................................................17

2.4 Special settings.........................................................................................................18

3 Error messages, troubleshooting..........................................................................19

3.1 Special messages and error messages ................................................................... 19

3.2 Diagnosis ................................................................................................................. 21

3.3 RAM initialisation....................................................................................................... 30

3.4 Releasing a locked spindle with insertd Exchange Unit...........................................31

4 Operation via RS232 Interface (green pages) ......................................................33

4.1 General .....................................................................................................................33

4.2 Control commands ................................................................................................... 34

4.3 Handshake and other properties..............................................................................45

4.3.1 Handshake full ...................................................................................................45

4.3.2 Handshake none................................................................................................45

4.3.3 General properties of the RS232 Interface......................................................... 46

4.4 Pin assignment of the RS232 / I/O socket ................................................................ 47

4.4.1 I/O socket, 25 pins ............................................................................................. 47

4.4.2 RS232 interface, 25 and 8 pin sockets ..............................................................48

5 Appendix.................................................................................................................51

5.1 Technical specifications............................................................................................ 51

5.2 Warranty and certificates .......................................................................................... 53

5.2.1 Warranty ............................................................................................................. 53

5.2.2 Certificate of Conformity and System Validation................................................ 54

5.3 Connection of a balance........................................................................................... 56

5.4 Connection of a printer .............................................................................................56

5.5 Continuous dosing with two Dosimats ..................................................................... 57

5.6 Scope of delivery and ordering designations ...........................................................59

Index...........................................................................................................................61

765 Dosimat

Overview

Explanation of symbols:

< > means "key", e.g. <GO> means key "GO"

DOS.....0.000 ml means "display"

765 Dosimat

1

Overview

1 Overview

Front view of instrument:

1 Exchange unit

Normally the models with automatic cock changeover.

Note:
Choose the volume of the exchange unit in such a way that a volume between

10...100% of the nominal volume is expelled.

2 Display
The 16 digit display shows all important information:

DOS 3.456 ml Mode (DOS = dosing) and dosed volume. Dosimat is in

stand-by position

DOS ↑ 3.456 ml The piston is moving upwards.
DOS ↓ 3.456 ml The piston is moving downwards.
DOS → 3.456 ml The cock is turned to the right.
DOS ← 3.456 ml The cock is turned to the left.

The display of the status
where movements of the piston cannot be clearly identified.

3 Operating keys at the Dosimat

<FILL> Filling. This key is (with remote control off) always accessible

<CLEAR> Resetting of the volume display to 0 with Dosimat in stand-by

<GO> Order to execute the current mode. With mode DOS, dosing

4 Setting of display contrast

5 Analogue setting of dosing rate

Position 1 = lowest rate

Position 10 = highest rate
The expelling and filling rates can be set separately (see page 6).

↑ resp.↓ are specially important for very slow dosings

and serves also as emergency stop.

position.

goes on as long as <GO> is pressed.

765 Dosimat

2

Overview

Rear view of instrument:

6 Data inputs and outputs

Via data transfer interface according to RS 232 C including optional analogue

output. For 25-pin D subminiature plug.
Important: Note plug positions, page 47!

Plug cables in and out only if the instruments are switched off.

7 Data inputs and outputs

Via data transfer interface according to RS 232 C. For 8-pin plug.
(For details see page 47)

Plug cables in and out only if the instruments are switched off.

8 Connection for keyboard

For details of operation with keyboard 6.2149.000 see page 4ff.

9 Power connection

In power supply systems, in which strong HF interferences (transients) are su­perimposed on the power voltage, the 765 Dosimat should be connected via an
additional power line filter, e.g. METROHM 615 model.
The main cables supplied with the instrument are three-core and equipped with
a plug with an earthing pin. If a different plug has to be fitted, the yellow/green
lead must be connected to the protective earth. Each break in the earthing inside
or outside the instrument can make it a hazard.
When the instrument is opened or if parts of it are removed, certain components
may be live if the instrument is connected to the power line. The power cable
must therefore always be unplugged when certain adjustments are made or
parts replaced.

10 Power switch

Switching on and off Dosimat. The 765 Dosimat is equipped with a non-volatile
memory, i.e. set parameters remain in the working memory if the Dosimat is
switched off and on.

11 Earthing socket

The 765 Dosimat must be grounded correctly and effectively, if necessary
through the separate earthing socket.

12 Connection for stirrer

In general a Magnetic Stirrer (forms a complete titrating stand). Other stirrers
may be connected as well, e.g. a METROHM Rod Stirrer. Supply voltage output:

+9 V DC (I # 200 mA).

13 Connection for external dosing contact

E.g. 6.2107.000 push button cable.

14 Indication of power voltage

Make sure the current has been adapted correctly before Dosimat is switched
on.

15 Identification plate
Indication of model, series and serial number.

765 Dosimat

3

2.1. Keypad

2 Operation with the keyboard

2.1 Keypad

RATE VOLUME EXP

BLANK

7

FACTOR

8

UNIT

4

STORE

5

1

2

0

.

FILL

GO CLEAR

6.2149.000

SMPL

9

RECALL

6

3

MODE

–

ENTER

RATE Expelling and filling rate in all modes.

VOLUME Different volumes depending on selected

mode.
EXP Exponent.
BLANK
FACTOR Calculation parameters in mode DOS.
SMPL

UNIT Unit in modes DOS and CNT

STORE Management of user memory:
RECALL Storing, loading of modes.

MODE Selection of mode.

ENTER Confirmation of entries.

FILL Filling and emergency stop key.

CLEAR Resetting of the volume display to 0 with

Dosimat in stand-by position.

GO Start mode. With mode DOS, dosing

goes on as long as <GO> is pressed.

The keys <FILL>, <CLEAR>, <GO> are identical
with the corresponding keys on Dosimat.

765 Dosimat

4

2.1 Keypad

Rules for data input:

• On entering a negative number, key in minus sign first; <-> is not a "change of sign"

key!

• Changeover between first functions (blank, factor etc.) and digits is done

automatically.

• Terminate parameter entries with <ENTER>.

• Some keys are organized as inquiry drums, i.e. pressing these keys several times, dis-

play shows new inquiries. A new value is stored or a new feature is selected with
<ENTER>. The program then returns to the initial state, the inquiry drum is left. Enter­ing an inquiry drum, that inquiry, where the drum has been left last time, is displayed
first.

• The Dosimat works with a resolution of 10'000 pulses per burette cylinder volume.

Exchange unit

Resolution of display

Volume/mL Rate mL/min

Smallest increment

V

1 mL .001 .001 0.1 µL

5 mL .001 .005 0.5 µL

10 mL .001 .010 1 µL

20 mL .002 .020 2 µL

50 mL .005 .050 5 µL

If a volume value is entered which can not be dosed exactly with the exchange unit on

the Dosimat, the value is rounded off to the next possible one and stored accordingly.
The smallest possible increments for 1 and 5 mL cylinders are not displayed. However,
they are dosed and the display is rounded.

• Key <CLEAR> sets parameters to "OFF".

765 Dosimat

5

2.2. Modes

2.1.1 Key <RATE>

The inquiries of this key are identical for all modes.

Expelling and filling rate

RATE

↑ ml/min

↓ ml/min

This key is accessible live (except in mode DOS), i.e. rate can be
changed during a running function .

Expelling rate
Range for digital setting depending on volume of exchange unit:

1 mL 0.001 3.00 mL/min
5 mL 0.005 15.0 mL/min
10 mL 0.010 30.0 mL/min
20 mL 0.020 60.0 mL/min
50 mL 0.050 150.0 mL/min

Key <CLEAR> sets "OFF", i.e.. the rate can be controlled
analogically by means of potentiometer at the Dosimat 765.

If the preset rate is too high to be dosed with the exchange unit
presently mounted, the rate is set automatically to its maximum.

Filling or aspirating rate
The data input rules are the same as for the expelling rate.

The filling rate is set to maximum on changing the exchange unit (e.g.
always after no exch. unit! is displayed!).

2.2 Modes

MODE

DOS: DOSing

DIS R: DISpensing, Repetitive

DIS C: DISpensing, Cumulative

PIP: PIPetting

DIL: DILuting

CNT D: CoNTent Dispenser

The modes are selected by the inquiry drum <MODE> and
confirmed with <ENTER>.

Dosimat is dosing as long as <GO> is pressed. Result calculation
can be activated.

Dosimat is dosing a stored dispensing volume if <GO> is pressed,
the burette cylinder is refilled and display reset to 0.000 mL.

Dosimat is dosing a stored dispensing volume if <GO> is pressed,
the dispensed volume (V-DIS) remains displayed.

Aspirating and subsequent expelling of a stored pipetting volume.

Aspirating a stored pipetting volume and subsequent expelling of the
pipetting and diluting volume.

Preparation of solutions with preselected content.

765 Dosimat

6

2.2 Modes

Example:
Selection of mode "DIS C", cumulative dispensing.

Press <MODE>.

Display shows that mode which has been selected last with key <MODE>, e.g.

DOS .

Press <MODE> repeatedly until display shows DIS C .

Load mode "DIS C" into working memory with <ENTER>.

Display shows DIS C 0.000 ml.

Mode "DIS C" is ready to work, the piston is in zero position.

All modes which are loaded into the working memory by key <MODE> are equipped
with a set of standard parameters:

Mode V-DIS/V-PIP

mL

V-LIM/V-DIL

mL

↑

Rate

mL/min

Rate ↓

mL/min

Calculation

DOS – OFF OFF max. b=0; f=1; s=1

DIS R 1 – OFF max. –

DIS C 0.1 OFF OFF max. –

PIP 0.1 – OFF OFF –

DIL 0.1 1 OFF OFF –

CNT D – – OFF max. –

2.2.1 Mode DOS, Dosing

Dosimat is dosing as long as <GO> is pressed. Result calculation can be activated.

VOLUME

V-LIM OFF ml

RATE

Security volume:
Dosing is stopped if V-LIM has been reached.
Input range: 0.001...999.999 mL, OFF

Expelling and filling rate, see page 6.

765 Dosimat

7

2.2. Modes

Calculation values

BLANK

FACTOR

7

8

SMPL

9

UNIT

4

b = 0. ml

f = 1.

s = 1.

unit

Blank value
Input range: 0...±999.999 mL

Factor
Input range: 0... ±1E33

Sample size
Input range: 0... ±1E33
Input manually or on-line with balance, see page 56

Unit
Input range: ppm, %, g, mg, g/L, mg/L, mol, mol/L, mL, L,
/pc, none

Result calculation
If one of the calculation values (blank, factor, smpl) is not set to its standard value, a

result is calculated on filling of the Dosimat according to formula:

(dosed volume–blank)*factor
Result = ————————————————
smpl

The result is recalculated on each entry of a calculation value (blank, factor, smpl).
Pressing <CLEAR> display shows the dosed volume in mL. To start a new dosing, press
<GO> twice, pressing once resets the volume in display to 0.000 mL.

Printing the result on a printer
If Dosimat is set to send RS 232 on (special settings see page 18), filling the Dosimat or

re-calculation triggers a print command. A continuous number (#), the dosed volume and
the calculated result are printed.
Do set new calculation parameters for the next dosing only after having pressed <GO>
once, i.e. if display shows DOS 0.000 ml.
The continuous number is set to zero on switching on the Dosimat and incremented by 1
on every filling command.

Example of print-out

#01 V = 0.352 ml R = 7.04 ppm
#02 V = 0.440 ml R = 8.8 ppm
#03 V = 0.000 ml
#04 V = 0.364 ml R = 7.28 ppm
#05 V = 0.438 ml R = 8.76 ppm
#06 V = 0.382 ml R = 7.64 ppm
#07 V = 0.370 ml R = 19.61 %
#08 V = 0.372 ml R = 19.72 %

765 Dosimat

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2.2 Modes

2.2.2 Mode DIS R, Repetitive Dispensing

Dosimat is dosing a stored dispensing volume if <GO> is pressed. The burette cylinder
is refilled and display reset to 0.000 mL.

Dispensing volume
Input range: 0.001...999.999 mL

VOLUME

V-DIS 1. ml

RATE

Expelling and filling rate, see page 6.

2.2.3 Mode DIS C, Cumulative Dispensing

Dosimat is dosing a stored dispensing volume if <GO> is pressed, and the dispensed
volume (V–DIS) remains displayed.

Dispensing volume
Input range: 0.001...999.999 mL
Security volume
Dispensing is stopped, if V-LIM has been reached.
Input range: 0.001...999.999 mL, OFF

Expelling and filling rate, see page 6.

VOLUME

RATE

V-DIS 0.1 ml

V-LIM OFF ml

Tandem Dosing
Mode DIS C is suitable for continuous dosing with 2 Dosimats, see page 57.

765 Dosimat

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2.2. Modes

2.2.4 Mode PIP, Pipetting

Aspirating and subsequent expelling of a stored pipetting volume.

VOLUME

V-PIP 0.1 ml

RATE

If mode PIP is loaded, the display shows PIP * 0.000 ml.
The sign * in the display means that mode "PIP" is not yet ready to be used. With a first
<GO>, a preparation step is carried out which is marked in the display with

PIP prep. . This preparation step includes the formation of an air bubble which

serves to separate the transfer solution of the exchange unit from the sample.
Then display shows PIP 1 0.100 ml, i.e. the Dosimat is ready to aspirate the pipetting
volume (0.1 mL). With <GO> the pipetting volume is aspirated and display shows

PIP 2 0.100 ml which means that the Dosimat is ready to expel the pipetting volume.

With the next <GO>, the volume is expelled and the Dosimat is then ready to aspirate
the next pipetting volume without any preparation step.

If the pipetting volume is changed, a new preparation step is always carried out.

Sequence of PIP

PIP * 0.000 ml

↓

<GO>

↓

PIP prep.

↓

PIP 1 0.100 ml

↓

<GO>

↓

PIP 2 0.100 ml

↓

<GO>

↓

Note

Pipetting volume
Input range depends on the volume of the exchange unit:

1 mL 0.001... 0.900 mL
5 mL 0.001... 4.900 mL
10 mL 0.001... 9.800 mL
20 mL 0.002... 19.700 mL
50 mL 0.005... 49.500 mL

Note: The liquid of the exchange unit is mixed with the
pipetted liquid if it is aspirated into the burette cylinder!
The aspiration tube must contain V-PIP!

Expelling and filling rate see page 6.

Standard mode PIP.

Preparation step: Hold burette tip free at working
height.
Ready to aspirate the pipetting volume: Immerse
burette tip.

Ready to expel the pipetting volume: Hold
burette tip for pipetting.

765 Dosimat

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2.2 Modes

• A new air bubble is built with every preparation step ("prep.") e.g. its volume increases.

If you wish to keep the volume of the air bubble expel it in mode DOS before changing
V-PIP.

• For best pipetting results we recommend exchange units with volumes ≤ 20 mL and

pipetting equipment 6.5611.000.

• The aspirating and expelling rates should not be higher than 20 mL/min.

• Hold tubing tip in an angle of app. 45° to the vessel wall during pipetting. Just the

same as you do with glass pipettes!

• The vessel, containing the liquid you want to pipette should stand on the same level as

the vessel into which you are going to expel the liquid in order to ascertain app. the
same level of the pipetting tubing during work.

2.2.5 Mode DIL, Diluting

Aspirating a stored pipetting volume and subsequent expelling of the pipetting and dilut­ing volume.

Pipetting volume
Input range depends on the volume of the exchange unit:

1 mL 0.001... 0.900 mL
5 mL 0.001... 4.900 mL
10 mL 0.001... 9.800 mL
20 mL 0.002... 19.700 mL
50 mL 0.005... 49.500 mL

Diluting volume
Input range: 0.001...999.999 mL

Note: The diluting liquid is unintentionally mixed with the
pipetted liquid if it is aspirated into the burette cylinder!
The aspiration tube must contain V-PIP!

Expelling and filling rate see page 6.

VOLUME

RATE

V-PIP 0.1 ml

V-DIL 1. ml

If mode DIL is loaded, the display shows DIL * 0.000 ml.
The sign * in the display tells you that mode DIL is not ready to be used. With <GO> a

preparation step is carried out during which V-PIP is expelled into the bottle of the
exchange unit and an air bubble is built to separate the solution of the exchange unit from
the sample.

Then the Dosimat is ready to aspirate the pipetting volume (0.1 mL) which is displayed by

DIL 1 0.100 ml and carried out after pressing <GO>.

Then DIL 2 1.100 ml is displayed which means that the Dosimat is ready to expel the
pipetting and the diluting volume (0.1 mL + 1 mL = 1.1 mL). This is executed after
<GO>. The preparation step is now carried out automatically and the Dosimat is ready to
aspirate the next pipetting volume.

765 Dosimat

11

2.2. Modes

Sequence of DIL

DIL * 0.000 ml

↓

<GO>

↓

DIL prep.

↓

DIL 1 0.100 ml

↓

<GO>

↓

DIL 2 1.100 ml

↓

<GO>

↓

DIL prep.

↓

Standard mode DIL.

Preparation step: Hold burette tip free at working
height.
Ready to aspirate the pipetting volume: Immerse
burette tip.

Ready to expel the pipetting and diluting volume:
Hold burette tip for pipetting.

Notes

• If you wish to change V-PIP, it is best to change it during filling in the preparation step,

i.e. when display shows DIL ↓ prep..

• If V-PIP is changed at another time, a new preparation step is carried out, which

changes the volume of the air bubble. The first dilution after such a change could be
erroneous and should be discarded. Another possibility is to expel the air bubble in
mode DOS and to start Mode DIL from the beginning. V-DIL can be changed at any
time without a new preparation step.

2.2.6 Mode CNT D, Content Dispenser

Mode CNT D is used to prepare solutions with a particular content. Doing this, the sub­stance must not be weighed-out to a particular value in order to obtain the preselected
content but the 765 Dosimat dispenses the amount of solvent calculated correspond­ingly.

RATE

Expelling and filling rate see page 6.

765 Dosimat

12

2.2 Modes

Content entries which can be implemented in the CNT D mode are summarized below
and designated with a bold frame

Reference quantity

(denominator)

Specified
quantity

(numerator)

Amount of

substance

/ mol

n

i

Mass

/ kg

m

i

Concentration Fraction Molality

Volume

of the solution

V / L

Amount of substance
concentration c

c

= ni/V

Units: mol/L, mmol/L
Example: c(NaOH)=0.1 mol/L
Outdated: molarity, molar

Mass concentration ρ

Units: g/L, mg/L
Example: ρ(Pb
Outdated: mg%

i

= mi/V

ρ

i

2+

)= 1 g/L

Amount of substance
fraction x

Unit: 1
Example: x(Au)=0.005
Outdated: mole fraction, mole

Mass fraction w

Units: %, ppm; 1
Example: w(H
Outdated: weight percent

Sum

of the components j

xi = ni/Σnj

percent

= mi/Σmj

w

i

O)= 5%

2

Mass

of the solvent

/ kg

m

k

Molality b

= ni//mk

b

Unit: mol/kg, mmol/kg
Example: b(KOH, in EtOH) = 1

i

mol/kg

Sequence of CNT D

CNT D 0.000 ml

↓

unit %

↓
↓

<ENTER>

↓

cnt 1 %

↓

Input <ENTER>

↓
↓
↓
↓
↓
↓

s 1 g

↓

Input <ENTER>

Standard mode CNT D. Display changes
automatically after preparation.
Choose unit by pressing key <UNIT>.
The volume is calculated according to the
chosen unit.

Input of the desired numerical value for the
content.
Depending on the unit selected the following
auxiliary variables are inquired during the first
run:

M 1 g/mol Molar mass of the substance
dens. 1 g/ml Density of the solvent
f 1.00000 Factor for volume contraction

Input of the weight manually or via a balance,
see page 56.

↓

add V XXX.XXX ml

↓ ↓
<GO> <CLEAR>

↓
dosing V

The calculated volume is displayed and expelled
with <GO>.
With <CLEAR> the values for "cnt" and/or "s" can
be changed. This gives an idea of the
approximate weighing.
Pressing <MODE>, the mode can be changed.

765 Dosimat

13

2.2. Modes

The formulae for calculation of the volume to be dispensed "add V" are shown in the
following table, with

cnt content in the selected unit
M molar mass of substance to be weighed out
f factor
dens density of the solvent
s weight of substance

Unit Formula for

add V =

Amount-of-substance
concentration

mol/L

mmol/L

f·s·10

f·s·10

cnt·M

6

3

cnt·M

3

f·s·10

Mass concentration

g/L

mg/L

cnt

f·s·10

6

cnt

2

f·s(10

Mass fraction

%

ppm

-cnt)

cnt·dens

6

f·s(10

-cnt)

cnt dens

Molality

mol/kg

mmol/kg

s·10

cnt·M·dens

s·10

3

6

cnt·M·dens

Application of factor f

Factor f for ionic standards

With ionic standards, the mass fraction of a single ion A is usually specified. On the other
hand, the solution is prepared from A
Pb(NO

. The factor f is calculated from the formula:

3)2

, e.g. a standard of 10 ppm Pb2+ prepared from

nBm

n*M(A) m*M(B)
f = ———— or f = ————
M(A

) M(AnBm)

nBm

M(A): molar mass of ion A
M(B): molar mass of ion B
M(A

): molar mass of substance AnBm

nBm

765 Dosimat

14

2.2 Modes

The following table shows factors for the most common ionic standards:

Cation Standard

prepared from:

Na+ NaCl

Factor f Anion Standard

prepared from:

0.39339

-

F

NaF 0.45245

Factor f

NaNO

3

K+ KCl

KNO

3

Ca2+ CaCl2 0.36111 Br- NaBr·2H2O

Ba2+ BaCl2·2H2O

Ba(NO

3)2

Cu2+ Cu(ClO4)2

Cu(NO

·6H2O

3)2

Pb2+ Pb(ClO4)2·3H2O

Pb(NO

3)2

PO

0.27050

0.52441

0.38670

0.56222

0.52550

0.24214

0.21494

0.45028

0.62557

-

Cl

NaCl

KCl

0.60666

0.47550

0.57514

KBr

-

I

KI 0.76444

2-

SO

K

4

-

NO

NaNO3

3

3-

Na2HPO4·12H2O

4

Na

3PO4

0.55087

2SO4

KNO

3

·12H2O

0.67141

0.72950

0.61319

0.26519

0.24985

The factor f as correction for substances with admixtures

e.g. water of crystallization, impurities, moisture.

The factor f as correction for the volume contraction

For the amount-of-substance concentration c (units mol/L and mmol/L) and the mass
concentration ρ (units g/L and mg/L), the concentration is referred to the volume of the
solution.

c

= ni/V resp. ρi= mi/V

i

where n
m

amount of substance i

i

mass of substance i

i

V volume of the solution

765 Dosimat

15

2.2. Modes

Since the volume of the solvent V0 is dispensed in the operational method of the CNT D
mode, higher concentrations require a correction factor which takes the difference
between V

and V (volume of the solution) into consideration:

0

V

0

f = —–
V

This factor can be determined with the Dosimat in the DOS mode:
A solution of the desired concentration is prepared in the conventional manner in a
volumetric flask by dispensing the solvent with the aid of the Dosimat up to the mark of
the flask (V

). If the volume V of the volumetric flask is inputted in the calculation

0

parameter "s", the factor f is calculated directly by the Dosimat and appears on the
display.
The factor f determined in this manner holds for the appropriate substance/solvent pair in
the measured concentration range with the possibility of linear extrapolations up to
concentrations of ca. 1 mol/L.

Several correction factors are shown in the following table:

Concentration c

0.05

mol/L

0.1 mol/L 1 mol/L

Substance/solvent

Potassium hydrogen

0.999 0.998 0.982

phthalate/water

Na2EDTA·2H2O/water 0.991 0.981 -

NaCl/water 0.999 0.998 0.982

KNO3/water 0.998 0.997 0.960

CuSO45H2O/water 0.995 0.992 0.904

765 Dosimat

16