Gebrauchsanleitung / Operating manual Labor-pH-Meter Laboratory pH Meter CG 842 ba12242de_2 09/99 Bedienungsanleitung Seite 1 Operating manual Page 45
Operating Manual Laboratory pH Meter CG 842 ba12242e_2 09/99 45
Accuracy when going to press All details contained in this operating manual are valid data at the time of going to press. However, SCHOTT may add details for both technical and commercial reasons, or in order to fulfil legal requirements of different countries. This does not affect the characteristics described. Warranty declaration The designated instrument is covered by a warranty of three years from the date of purchase.
List of contents 1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 1.1 1.2 1.3 1.4 1.5 2 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Declaration of conformity . . . . . . . . . . . . . . . . . . . . . 52 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Safety .
List of contents 48
Overview 1 Overview The compact CG 842 precision pH meter lets you perform pH measurements rapidly and reliably. The CG 842 provides the highest degree of operating comfort, reliability and measuring safety for all applications. The proven calibration procedures and special AutoRead function support your work with the pH meter. 3 2 1 Keypad 2 Display 3 Sockets 1 Note The measuring instrument can also be delivered as part of a set.
Overview 1.
Overview 1.2 Display Status line Measured value display Function and temperature display 1.3 Sockets 1 2 3 4 1 Socket according to DIN 19262/BNC 2 Pt1000/NTC30 connector for pH combined electrodes with temperature probe 3 Reference electrode connector 4 Connector for plug-in power supply (optional) Caution Only connect probes to the instrument that cannot feed excessive voltages or currents (> SELV and > circuit with current limiter).
Overview 1.4 Declaration of conformity 29.03.99 SCHOTT Geräte GmbH Im Langgewann 5 D 65719 Hofheim am Taunus Deutschland, Germany, Allemagne 29.
Overview 1.5 Ambient temperature Measuring ranges and resolution Measuring accuracy (± 1 digit) Technical data Storage temperature - 25 °C ... + 65 °C Operating temperature 0 °C ... + 55 °C Allowable relative humidity Annual mean: < 75 % 30 days/year: 95 % Other days: 85 % pH (resolution selectable) - 2.000 ... + 16.000 - 2.00 ... + 16.00 U [mV] - 999.9 ... + 999.9 - 1999 ... + 1999 T [°C] - 5.0 ... + 100.0 T [°F] + 23.0 ... + 212.
Overview Housing EMC and VDE norms Test marks Length [mm] 230 Width [mm] 210 Height [mm] 70 Weight [kg] Approx. 0.850 Material ABS Interference emission (generic standard) EN 50081-1 FCC class A Interference immunity (generic standard) EN 50082-1 Protective class 3, EN61010-1 Climatic class 2, VDI/VDE 3540 TÜV GS, UL/CUL, CE 1 Display Temperature compensation Keypad 54 Multifunctional LCD Automatically with Pt 1000/NTC (30 kW) -5 ... 99.9 °C Manual input -20 ...
Overview Energy supply Batteries 4 x 1.5 V AA type alkaline manganese batteries Runtime Approx. 3000 operating hours Mains power supply (option) Connection max. overvoltage category II (valid for all plug-in power supply units): Plug-in power supply (Euro plug): Type no.: Z851 Order no.: 28 520 4897 FRIWO FW3288, 11.8134 Friwo Part No. 1816492 Input: 230V ~ / 50 Hz / 23 VA Output: 6 V = / 1,8 A /10,8 VA Plug-in power supply (US plug): Type no.: Z852 Order no.: 28 520 4901 FRIWO FW3288, 11.
Overview Connections Input amplifier Calibration modes 56 Electrodes Socket according to DIN 19 262 or BNC 4 mm socket for reference electrode Temperature probe 4 mm socket for temperature probe Plug-in power supply unit 2-pole special Friwo Input impedance ≥ 1012 Ω Offset current ≤ 10-12 A AutoCal TEC With Technical buffers (given in pH): 2.00; 4.00; 7.00; 10.00 at 25 °C; buffers are temperature compensated in the range 0 ...
Safety 2 Safety This operating manual contains basic instructions that you must follow during the commissioning, operation and maintenance of the pH meter. Consequently, all responsible personnel must read this operating manual before working with the instrument. The operating manual must always be available within the vicinity of the instrument. Target group This measuring instrument was developed for use in the laboratory.
Safety 2.1 Authorized use This instrument is authorized exclusively for pH and Redox measurements in the laboratory. The technical specifications as given in the chapter, TECHNICAL DATA, must be observed. Only the operation and running of the measuring instrument according to the instructions given in this operating manual is authorized. Any other use is considered unauthorized. 2.
Safety Safe operation If safe operation is no longer possible, the instrument must be taken out of service and secured against inadvertent operation. Safe operation is no longer possible if: l the instrument has been damaged in transport l the instrument has been stored under adverse conditions for a lengthy period of time l the instrument is visibly damaged l the instrument no longer operates as described in this manual If you are in doubt contact the supplier of the instrument.
Safety 60
Commissioning 3 Commissioning Perform the following activities for the initial commissioning: Setting °C or °F l Set the °C or °F l Set the resolution l Connect the plug-in power supply (optional). The temperature can be displayed in °C or in °F . In the delivery condition, the measuring instrument is preset to °C. To change the unit proceed as follows: 1 Switch the measuring instrument off. 2 Press and hold down the key. 3 Press the key.
Commissioning 3 Press the and keys again. The measured values are displayed with a low resolution, e. g. pH = 4.01. Connecting the plug-in power supply (optional) The measuring instrument works battery-powered. It can, however, also be supplied by the plug-in power supply which is available as an accessory. Warning The line voltage on site must lie within the input voltage range of the original plug-in power supply unit (see section 1.5 TECHNICAL DATA).
Operation 4 Operation 4.1 Switch on the instrument 1 Place the instrument on a flat surface and protect it against intense light and heat. 2 Press the key. The display test appears briefly on the display. The instrument then switches automatically to the previously selected measuring mode. 3 Connect the pH electrode to the instrument. The measuring instrument is ready for operation. Note The instrument has an energy saving feature to avoid unnecessary battery depletion.
Operation 4.2 Preparatory activities Measuring Perform the following activities when you want to measure: 1 Connect the pH electrode to the instrument. 2 Adjust the temperature of the buffer or test solutions or measure the current temperature if the measurement is made without a temperature probe. 3 Calibrate or check the instrument with the pH electrode according to section 4.3. 4 Select the measuring mode by pressing .
Operation 4.2.1 Measuring the pH value 1 Perform the preparatory activities according to section 4.2. 2 Immerse the pH electrode into the test sample. 3 Press the key until pH appears in the status display. The pH value appears on the display. AutoRead AR (Drift control) The AutoRead function (drift control) checks the stability of the measurement signal. The stability has a considerable effect on the reproducibility of the measured values.
Operation Note The current AutoRead measurement (with acceptance of the current value) can be terminated at any time by pressing . 4.2.2 Measuring the Redox voltage The pH meter can measure the Redox voltage (mV) of a solution when connected with a Redox electrode, e.g. BlueLine 31 Rx. 1 Perform the preparatory activities according to section 4.2. 2 Immerse the Redox electrode into the test sample. 3 Press the key repeatedly until U appears in the status line.
Operation 4.3 Why calibrate? Calibrating pH electrodes age. This changes the asymmetry (zero point) and slope of the pH electrode. As a result, an inexact measured value is displayed. Calibration determines the current values of the asymmetry and slope of the electrode and they are stored in the instrument. Thus, you should calibrate at regular intervals. Note Always calibrate after connecting another electrode.
Operation Calibration evaluation After the calibration, the instrument automatically evaluates the current status. The asymmetry and slope are separately evaluated. The worst evaluation appears on the display. Display Asymmetry [mV] Slope [mV/pH] -15 ... +15 58 ... 60.5 -20 ... +20 57 ... 58 -25 ... +25 56 ... 57 or 60.5 ... 61 -30 ... +30 56 ... 50 or 61 ...
Operation 4.3.1 AutoCal TEC Use any two of the Technical Buffer Solutions for this procedure. Note Steps 2 and 6 are not required if you use a temperature probe. 1 Press the key repeatedly until Ct1 and the AutoCal TEC function display appear. 2 If necessary, set the temperature of the buffer solution by pressing <▲> <▼> . 3 Submerse the pH electrode in the first buffer solution. 4 Press the key. AR flashes on the display. The electrode voltage (mV) appears on the display.
Operation 6 If necessary, set the temperature of the second buffer solution by pressing <▲> <▼>. 7 Submerse the electrode in the second buffer solution. 8 Press the key. AR flashes on the display. The electrode voltage (mV) appears on the display. As soon as a stable value is recognized, AR disappears. The sensor symbol shows the electrode evaluation after the two-point calibration. The value of the slope (mV/pH) appears on the display. 9 Press the key.
Operation 4.3.2 AutoCal DIN Use two different DIN buffer solutions for this procedure: DIN buffer solution pH A 1.68 C 4.01 D 6.87 F 9.18 Note Steps 2 and 6 are not required if you use a temperature probe. 1 Press the key repeatedly until Cd1 and the AutoCal DIN function display appear. 2 If necessary, set the temperature of the buffer solution by pressing <▲> <▼>. 3 Submerse the pH electrode in the first buffer solution. 4 Press the key. AR flashes on the display.
Operation 5 Thoroughly rinse the electrode with distilled water. 6 If necessary, set the temperature of the second buffer solution by pressing <▲> <▼>. 7 Submerse the electrode in the second buffer solution. 8 Press the key. AR flashes on the display. The electrode voltage (mV) appears on the display. As soon as a stable value is recognized, AR disappears. The sensor symbol shows the electrode evaluation after the two-point calibration. The value of the slope (mV/pH) appears on the display.
Operation 4.3.3 ConCal Two-point calibration Use two buffer solutions for this procedure: l pH 7.0 ± 0.5 l any other buffer solution Note Steps 2 and 9 are not required if you use a temperature probe. 1 Press the key repeatedly until ASY and the ConCal function display appear. 2 If necessary, set the temperature of the buffer solution by pressing <▲> <▼>. 3 Submerse the pH electrode in the pH 7.0 ± 0.5 buffer solution. 4 Press the key. The measured pH value appears on the display.
Operation 8 Thoroughly rinse the electrode with distilled water. 9 If necessary, set the temperature of the second buffer solution by pressing <▲> <▼>. 10 Submerse the electrode in the second buffer solution. 11 Press the key. The second measured pH value appears on the display. 12 Set the nominal pH value of the second buffer solution (at the current temperature). 13 Press the key. The value of the slope (mV/pH) appears on the display.
Operation Single-point calibration Use a buffer solution in the range pH = 7.0 ± 0.5 for this procedure. Note Only the electrode asymmetry is determined in single-point calibration. The slope of the last two-point calibration is retained. Note Step 2 is not required if you use a temperature probe. The TP display indicates an active temperature measurement. 1 Press the key repeatedly until ASY and the ConCal function display appear. 2 Set the temperature of the buffer solution by pressing <▲> <▼>.
Operation 4.4 Basic settings Reset The following functions are reset (initialized) to the values they had on delivery: Measuring mode pH Asymmetry 0 mV Slope -59.16 mV/pH Calibration procedure AutoCal TEC Temperature, manual 25°C Resolution of pH display 0,01 Proceed as follows: 1 Press and hold down the key. 2 Press the key. 3 Toggle between no and yes by pressing <▲> <▼>. yes: reset parameters. no: retain settings. 4 Confirm with .
Maintenance, cleaning, disposal 5 Maintenance, cleaning, disposal 5.1 Maintenance The measuring instrument is almost maintenance-free. The only maintenance task is replacing the batteries: 1 Open the battery compartment (1) on the underside of the instrument. 2 Remove the four batteries from the battery compartment. 3 Insert four new batteries (Type Mignon AA) into the battery compartment. 4 Close the battery compartment (1).
Maintenance, cleaning, disposal 5.2 Cleaning Occasionally wipe the outside of the measuring instrument with a damp, lint-free cloth. Disinfect the housing with isopropanol as required. Caution The housing is made of synthetic material (ABS). Thus, avoid contact with acetone or similar detergents that contain solvents. Remove any splashes immediately. 5.3 Disposal Packing The measuring instrument is sent out in a protective transport packing. We recommend: Keep the packing material.
What to do if... 6 Error message, I / Error message, What to do if...
What to do if... Buffer solutions: No stable measured value – Incorrect buffer solutions – Change calibration procedure – Buffer solutions too old – Only use once.
What to do if...
What to do if...
Lists 7 Lists This chapter provides additional information and orientation aids. Abbreviations The list of abbreviations explains abbreviations that appear on the display or when dealing with the instrument. Specialist terms The glossary briefly explains the meaning of the specialist terms. However, terms that should already be familiar to the target group are not described here. Index The index helps you find the topics that you are looking for.
Lists Abbreviations 84 AR AutoRead (drift control) ARng Automatic range switching Measuring instrument measures with highest resolution ASY Asymmetry AutoCal DIN Automatic calibration with DIN buffer solutions AutoCal TEC Automatic calibration with Technical Buffer Solutions Cal Calibration Cd... Calibration with DIN buffer solutions (acc. to DIN 19 266) ConCal Conventional one/two point calibration Ct... Calibration with Technical Buffer Solutions E3 Error message (see WHAT TO DO IF .
Lists TP Temperature probe Temperature measurement active UASY Asymmetry potential °C Temperature unit, °Celsius °F Temperature unit, Fahrenheit 85
Lists Glossary Asymmetry Zero point of a pH electrode. Resolution Number of decimal places that appear for a measured value. AutoRead Monitors the electrode drift and releases the measured value only after the stability criterion has been reached. In this way, this procedure ensures the highest degree of precision and reproducibility. Diaphragm Drift control Test solution Buffer solution Redox voltage Slope 86 Contact point between the reference electrolytic solution and the sample.
Lists Index A P asymmetry 67 authorized use 58 AutoCal DIN 67, 71 AutoCal TEC 67, 69 AutoRead 65 place of the instrument 63 plug-in power supply 62 power supply 54, 62 B basic settings 76 battery compartment 77 Buchsenfeld 51 R Redox electrode 66 Redox voltage 66 replacing the batteries 77 reset 76 S C calibrating 67 calibration evaluation 68 calibration procedures 67 ConCal 67, 73 D delivery condition 76 display 51 drift control 65 E energy saving feature 63 error messages 79 safety 57 safety pr
