Operating Manual Laboratory pH Meter CG 843 ba12243e_2 09/99 69
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 1.1 1.2 1.3 1.4 1.5 2 Keypad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74 Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 Declaration of conformity . . . . . . . . . . . . . . . . . .76 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . .77 Safety . . . . . . . . . . . . . . . . . . .
List of contents 5 Maintenance, cleaning, disposal . . . . . . . . . 125 5.1 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . .125 5.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 5.3 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 72 6 What to do if... . . . . . . . . . . . . . . . . . . . . . . . . 127 7 Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overview 1 Overview The compact CG 843 precision pH meter lets you perform pH measurements rapidly and reliably. The CG 843 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 1 Keypad 2 Display 3 Sockets 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 5 1 Socket according to DIN 19262/BNC 2 PT 1000/NTC30 connection for pH combined electrode with temperature probe 3 Reference electrode connection 4 RS 232 interface/analog output 5 Connection 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 Technical data Ambient temperature Measuring ranges and resolution Measuring accuracy (± 1 digit) Storage temperature - 25 °C ... + 65 °C Operating temp. 0 °C ... + 55 °C Allowable relative humidity Annual mean: < 75 % 30 days/year: 95 % Other days: 85 % pH - 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 ... + 212.0 resolution selectable Given as measuring uncertainty at a confidence level of 95%.
Overview Housing EMC and VDE norms Test marks 78 Length [mm] 230 Width [mm] 210 Height [mm] 70 Weight [kg] Approx. 1.
Overview Power supply Batteries 4 x 1.5 V AA type alkaline manganese batteries Runtime Approx. 3000 operating hours Mains power supply (option) Plug-in power supply unit: Connection max. overvoltage category II 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, 11.8451 Friwo Part No.
Overview Connectors Input amplifier Calibration modes 80 Electrodes Socket acc. to DIN 19 262 or BNC 4-mm socket for reference electode Temp. probe 4-mm socket for temperature probe Interface/ analog output Bidirectional RS 232 interface or analog output with autom. recognition of the PC, printer, or recorder connected Plug-in power supply (option) 2 pole special Friwo Input impedance 1012 W Offset current 10-12 A AutoCal TEC With Technical buffers, pH values 2.00; 4.00; 7.00; 10.
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 section 1.5 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 84
Commissioning 3 Commissioning Perform the following activities for the initial commissioning: Setting the date and time l Set the date and time l Connect the plug-in power supply. 1 Press and hold down the key. 2 Press the key. The display test appears briefly on the display. The measuring instrument then switches automatically to the setting of the baud rate. 3 Press the key repeatedly until the date flashes on the display. 4 Set today’s date by pressing <▲> <▼>.
Commissioning 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). Caution Use original plug-in power supplies only (see section 1.5 TECHNICAL DATA). 2 1 3 1 Insert the plug (1) into the socket (2) of the pH meter.
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. Note The instrument has an energy saving feature to avoid unnecessary battery depletion. The energy saving feature switches the instrument off if no key has been pressed for an hour.
Operation 4.2 Preparatory activities Measuring Perform the following preparatory activities when you want to measure: 1 Connect the 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 electrode according to section 4.3 CALIBRATING. 4 Select the measuring mode by pressing .
Operation Temperature probe Measurements can be performed with and without a temperature probe. A connected temperature probe is indicated by TP on the display. Note The pH meter automatically recognizes the type of the temperature probe used. As a result, you can connect electrodes with the NTC30 or Pt1000. The temperature measurement is absolutely essential for a reproducible pH measurement.
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 4.2.3 Transmitting measured values You can transmit measured values (data records) in 3 ways: l Switch on the data transmission (Int 2) (see 114) – After expiry of the selected interval, the current data record is sent to the RS interface. l Switch on AutoStore (Int 1) (see section 4.4.
Operation 4.3 Why calibrate? When to 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.
Operation Calibration protocol The calibration protocol contains the calibration data of the current calibration. You can call up the calibration protocol by outputting the data storage (section 4.4.3). Note You can automatically print out a calibration protocol after the calibration. To do so, connect a printer according to section section 4.5.3 before the calibration. After a valid calibration, the protocol is printed. Sample printout: CALIBRATION PROTOCOL 02.03.99 14:19 Device No.
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 Calibration interval (Int 3) The flashing sensor symbol reminds you to calibrate regularly. After the selected calibration interval (Int 3) expires, the sensor symbol flashes. Measurements can continue. Note To ensure the high measuring precision of the measuring system, perform a calibration after the calibration interval expires. Setting the calibration interval The calibration interval (Int 3) is set to 7 days in the factory. The interval can be changed (1 ...
Operation 4.3.2 AutoCal TEC Use any two or three of the Technical buffer solutions for this procedure in increasing or decreasing order. Note Steps 2, 6 and 13 are not required if you use a temperature probe. 1 Press the key repeatedly until Ct1 and the AutoCal TEC function display appears. 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 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 Three-point calibration 11 Press the key. Ct3 appears on the display. 12 Thoroughly rinse the electrode with distilled water. 13 If necessary, set the temperature of the third buffer solution by pressing <▲> <▼>. 14 Submerse the electrode in the third buffer solution. 15 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.
Operation 4.3.3 AutoCal DIN Use two or three different DIN buffer solutions for this procedure in increasing or decreasing order. DIN buffer solution pH A 1.68 C 4.01 D 6.87 F 9.18 Note Steps 2, 6 and 13 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.
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 Three-point calibration 11 Press the key. Cd3 appears on the display. 12 Thoroughly rinse the electrode with distilled water. 13 If necessary, set the temperature of the third buffer solution by pressing <▲> <▼>. 14 Submerse the electrode in the third buffer solution. 15 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.
Operation 4.3.4 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 first buffer solution pH 7.0 ± 0.5. 4 Press the key.
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 message 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 Storing The pH meter has an internal data storage device. Up to 200 data records can be stored in it. A complete data record consists of: l Memory location l Date l Time l Measured value l Temperature l Temperature measurement procedure l I.D. number You can transmit measured values (data records) to the data storage in 2 ways: l Manual storage l Switching on the AutoStore function (Int 1). 4.4.
Operation 2 Confirm with . The display changes to the input of the I.D. number. 3 Enter the required I.D. number (1 ... 999) by pressing <▲> <▼>. 4 Confirm with . The instrument changes to the measuring mode. *( +,, message This message appears if all 200 memory locations are full. You have the following options: Store the current measured value.
Operation 4.4.2 Switching on AutoStore (Int 1) The storage interval (Int 1) determines the time interval between automatic storage processes. After the time interval expires, the current data record is transmitted to the data storage and to the RS interface. Setting the storage interval The storage interval (Int 1) is set to OFF in the factory. Thus, the AutoStore function is switched off.
Operation 5 As soon as all 200 memory locations are full, the AutoStore function is terminated (Int 1 = OFF). If too few storage locations are available for your measurements: – backup the data storage (see 110) and – clear the data stored (see 113). 6 Confirm with . The prompt for the I.D. number appears on the display. 7 Press <▲> <▼> to set the required I.D. number. 8 Confirm with . The instrument changes to the pH measuring mode and starts the measuring and storage procedure.
Operation 4.4.3 Outputting the data storage The contents of the data storage can be output to the: Outputting to the display l display l RS interface 1 Press the key repeatedly until Sto disp appears on the display. 2 Press the key. A measured value appears on the display. The memory location of the data store appears for approx. 2 s. This is followed by the corresponding temperature. You can perform the following activities: Display further parameters of the data record (I.D. no.
Operation 1 Select the parameter (e.g. date) by pressing . 2 Press <▲> or <▼> repeatedly until the required date appears on the display. After approx. 2 s, the temperature of the displayed measured value appears. Outputting to RS interface 1 Press the key repeatedly until Sto SEr appears on the display. 2 Press the key. Sto CAL appears on the display. The calibration protocol is transmitted to the RS interface.
Operation Sample printout: CALIBRATION PROTOCOL 02.03.99 14:19 Device No.: 12345678 CALIBRATION pH Cal Time: 01.03.99 / 15:20 Cal Interval: 7d AutoCal DIN Tauto Buffer 1 1.679 Buffer 2 4.008 * Buffer 3 6.865 Buffer 4 9.180 * C1 174.1mV 25.0°C C2 -133.3mV 25.0°C S1 -59.4 mV/pH ASY1 4 mV Probe: +++ No. 1: 09.03.99 pH 10.01 Tman Ident : 1 No. 2: 09.03.99 pH 10.01 Tauto Ident : 1 No. 3: 09.03.
Operation 4.4.4 Clearing the storage This function can erase the stored data records. 200 memory locations will then become available again. Note The Clear store function only appears if data records have already been stored in the storage. Otherwise, the pH meter automatically changes to the measuring mode. In order to delete all the data records, proceed as follows: 1 Switch off the instrument. 2 Press and hold down the key. 3 Press the key.
Operation 4.5 Data transmission You can use the following options to transmit data: l One of the following options: – The AutoStore function (108) is used to periodically (Int 1 storage interval) save measured values internally and output them on the RS interface. – The data transmission interval (Int 2) function is used to periodically output measured values to a RS interface (see below).
Operation Setting the data transmission interval The interval is set to OFF in the factory. To start the data transmission, set up an interval (5 s, 10 s, 30 s, 1 min, 5 min, 10 min, 15 min, 30 min, 60 min): 1 Press and hold down the key. 2 Press the key. Int 2 appears on the display. 3 Press <▲> <▼> to set up the required time interval between storage processes. 4 Confirm with . The instrument changes automatically to the pH measuring mode.
Operation 4.5.2 Recorder (analog output) You can transmit the data to a recorder via the analog output. Connect the analog output to the recorder via the Z394 RS interface cable. The data output switches automatically to recorder output. Socket assignment 1 4 2 3 RS 232 REC 1 Free 2 Plug coding 3 Ground 4 Analog output low impedance electrode signal corresponds to 50 ... 62 mV/pH (internal resistance < 5 Ohm) Note Activate the analog output by connecting 2 and 3.
Operation 4.5.3 PC/external printer (RS232 interface) You can transmit data to a PC or an external printer via the RS232 interface. Connect the RS interface to the instrument via the Z395 cable (PC) or Z391 cable (external printer). The data output switches automatically to RS232. Note The RS232 interface is not galvanically isolated.
Operation 4.6 Configuration You can adapt the pH meter to your individual requirements. To do this, the following parameters can be changed (the status on delivery is marked in bold): Baud rate 1200, 2400, 4800, 9600 Data transmission interval (Int 2) OFF, 5 s, 10 s, 30 s, 1 min, 5 min, 10 min, 15 min, 30 min, 60 min Calibration interval (Int 3) 1 ... 7 ... 999 d Temperature unit °C, °F Date/time As required Resolution of pH display 0.01, 0.
Operation Baud rate 4 Set up the required baud rate by pressing <▲> <▼>. 5 Confirm with . Int 2 appears on the display. Data transmission interval 6 Set up the required time interval by pressing <▲> <▼>. 7 Confirm with . Int 3 appears on the display.
Operation 8 Set up the required time interval by pressing <▲> <▼>. 9 Confirm with . USE °C appears on the display. Temperature unit 10 Change between °C and °F by pressing <▲> <▼>. 11 Confirm with . The date flashes on the display. Date and time 12 Set today’s date by pressing <▲> <▼>. 13 Confirm with . The date (month) flashes on the display. 14 Set the current month by pressing <▲> <▼>. 15 Confirm with . The year appears on the display.
Operation 16 Set the current year by pressing <▲> <▼>. 17 Confirm with . The hours flash on the display. 18 Set the current time by pressing <▲> <▼>. 19 Confirm with . The minutes flash on the screen. 20 Set the current time by pressing <▲> <▼>. 21 Confirm with . The instrument changes automatically to the pH measuring mode. Adjusting the resolution 1 Press and hold down the key. 2 Press the key.
Operation 4.7 Reset You can reset (initialize) measuring and configuration parameters separately from one another. Measuring parameters The following measuring parameters (pH InI) are reset 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 Note When the measuring parameters are reset, the calibration data are lost.
Operation Resetting measuring parameters 1 Press and hold down the key. 2 Press the key. 3 Use <▲> <▼> to toggle between no and yes. yes: reset measuring parameters. no: retain settings. 4 Confirm with . The instrument changes to the configuration parameters. Resetting configuration parameters 5 Toggle between no and yes by pressing <▲> <▼>. yes: reset configuration parameters. no: retain settings. 6 Confirm with .
Operation 124
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 batteries from the battery compartment. 3 Insert four new batteries (Type Mignon AA) into the battery compartment. 4 Close the battery compartment (1). The date (day) flashes on the display.
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... LoBat display *( display Obviously incorrect measured values Instrument does not react to keystroke *( +,, message Cause Remedy – Batteries almost depleted – Replace batteries (see section 5.
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 132 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...
Lists RCL Recall memory dump S Slope SELV Safety Extra Low Voltage SEr Serial interface Output of the data storage on the RS 232 or on the internal printer SLO Slope Slope setting on calibration Sto Store Memory TP Temperature probe Temperature measurement active UASY Asymmetry potential °C Temperature unit, °Celsius °F Temperature unit, Fahrenheit 133
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. Baud rate Transmission rate in bits/s. Diaphragm Drift control See AUTOREAD. Test sample Sample to be measured (can be liquid or solid).
Lists Index calibration 96 data transmission 114 storing 108 A analog output 116 asymmetry 93 authorized use 82 AutoCal DIN 93, 100 AutoCal TEC 93, 97 AutoRead 90 K B LoBat 129 battery compartment 125 baud rate setting 119 M C O calibrating 93 calibration evaluation 95 interval 96 procedures 93 protocol 94 ConCal 93, 103 condition on delivery 122 D data record 106 data transmission (interval) 115 date setting 85, 120 display 75 drift control 90 E energy saving feature 87 error messages 127 I in
Lists sockets 75 T temperature probe 89 three-point calibration 93 AutoCal DIN 102 AutoCal TEC 99 time setting 85, 120 two-point calibration 93 AutoCal DIN 101 AutoCal TEC 98 ConCal 103 136
