Getting Started TWO-POINT CALIBRATION--QUICK REFERENCE GUIDE

Transcription

1 Getting Started TWO-POINT CALIBRATION--QUICK REFERENCE GUIDE Connect probe to meter. Put probe in first calibrating buffer. Press ON/OFF to turn on meter If necessary, press ph until ph status indicator arrow points to ph. Status indicator arrow should NOT point to BUFFER. Press CAL, then CLEAR to clear the previous calibration. Status indicator arrow will point to 1PT. Meter will automatically identify the first buffer solution. If necessary, press SELECT BUFFER until display matches first buffer value. Press ENTER and wait until the large number display stops flashing. Rinse probe in dionized water and place in second calibrating buffer Press CAL. Status indicator arrow will point to both 1PT and 2PT. Meter will automatically identify the second buffer solution. If necessary, press SELECT BUFFER until display matches second buffer value. Press ENTER and wait until the large number display stops flashing. Rinse probe in dionized water and place in sample. 1

2 INTRODUCTION IMPORTANT NOTICE IF THE METER IS USED IN A MANNER OTHER THAN AS DESCRIBED, THE SAFETY AND PERFORMANCE OF THE METER CAN BE IMPAIRED. This system uses an Ion Sensitive Field Effect Transistor (ISFET) ph sensor. There is no glass to break and the probe should be stored dry. No electrode storage solution is required. The Ò3-in-1Ó probe contains the ph sensor, reference electrode, and temperature sensor. ESTIMATED LIFE OF AN ISFET SENSOR ph PROBE Depending upon the application, the expected life of an ISFET probe is approximately 18 months. The reference electrode contains a KCl gel which becomes increasingly diluted with usage and time. The reference is sealed and is not refillable. When it becomes difficult to calibrate (ph buffer value does not stop flashing during calibration or takes an excessively long time to stop flashing) the probe should be replaced. A probe that is dirty, miscalibrated, or has reached the end of its useful life will give an error message E11 on the meter display. Your ISFET probe is warranted to be free from manufacturing defects for six (6) months from the date of purchase. 2

3 Table of Contents Getting Started--Quick Reference Guide for Two Point Calibration Techniques and Tips For Best Performance Display Features and Meter Connections Main Display Meter Connections Status Indicators Keypad Functions Cleaning and Reconditioning the Probe ph Calibration and Measurement Important Notes for Best Calibration Results Calibration With Two Buffers Calibration With Three Buffers Calibration With One Buffer How to Abort Calibration Automatic Buffer Recognition Automatic Temperature Compensation of Automatic Buffer 17 Recognition Values.. Changing Stored Automatic Buffer Recognition Values Restoring Automatic Buffer Recognition Values to Factory Default. 18 mv Measurement Storing and Recalling Data Storing Sample Readings Recalling Sample Readings Clearing Data from One Storage Address Clearing Data from All Storage Addresses Output Modes Analog Output Serial Output Output of Calibration Data to the Serial Port Output of Current Sample to the Serial Port Output of the Contents of a Single Memory Address 23 Output of the Contents of all Memory Addresses 23 Setting the Baud Rate Temperature Calibration User Temperature Calibration Restoring Temperature Calibration to Factory Default Battery Replacement Troubleshooting Error Codes

4 Techniques and Tips for Best Performance DO: Soak the probe in ph 7.00 buffer for at least five minutes if the probe is new or has been stored dry for an extended period. This will hydrate the sensor and dissolve any reference material, which may have crystallized on he sensor surface. DO DO: Clean the probe regularly with a toothbrush and mild detergent. DO: STORE THE PROBE DRY with the black protective cap covering the probe tip. No electrode storage solution is required. DO: Always begin each measuring session with a two-point calibration. Update often with one-point or two-point calibrations. DO: Use fresh buffers and deionized rinse solution. DO: Use buffer solutions with ph values no greater than three ph units apart. Buffers should bracket the anticipated values of the samples to be measured. DO: Choose buffer solutions that most closely mimic the chemical nature and conductivity level of the sample solutions to be measured. DO: Use deionized water to rinse residual buffer and sample solutions from the probe after calibration and measurement. DO: Calibrate at the same temperature as the sample solution. Although the meter has automatic temperature compensation, best results will be achieved if he calibration buffers and sample are the same temperature. DO: Keep the connectors clean and dry. Dirty or damp connectors can cause unstable readings. DO: Be sure the surface of the sensor in the probe is free from any deposits or films. See the cleaning instructions in this manual. DO: Contact IQ Scientific Instruments if your ph testing involves monitoring small ph changes over time (i.e. titrations). 4

5 DO NOT DO NOT change probes while the meter is turned on. Always turn off the meter before changing probes. DO NOT store the probe in solution or use for long term ph measuring applications. Extended immersion will shorten the life of the probe. DO NOT leave probe uncapped for long periods of time. Always place the protective cap over the probe tip when finished measuring. DO NOT allow oil, fat, food particles, starch, protein, or other materials to remain on the probe tip after use. DO NOT use a sharp metal object (needle, pin, etc.) to clean the sensor surface. DO NOT take readings in direct sunlight. Direct sunlight may cause unstable readings or difficulty in calibration. DO NOT use the probe in an environment that will damage ph sensor, such as hydrofluoric acid or abrasive samples. DO NOT use the probe in environments that will damage the epoxy materials used in probe construction, such as, acetone, toluene, methylene chloride, xylene, and other strong organic solvents. DO NOT use in environments with static electricity. Electrostatic discharge may permanently damage the probe. DO NOT use the probe for extended periods at temperatures over 60 o C. Use at elevated temperature will reduce the life of the probe. DO NOT put any other active measurement devices in buffers or samples while measuring ph. Even if another device is not actually turned on, AC power interference can still occur, especially if the ph meter AC battery adapter is in use. 5

6 1. Main Display 2. Temperature Display. 3. AUTO HOLD Mode Indicator 4. Status Indicator Arrows 5. Serial Interface (RS-232) 6. AC Adapter Connector 7. Recorder Output 8. Probe Connector Main Display The large digits show the following: 1. Readout of the measured value, either ph or millivolt. 2. Memory address display ÒAXXÓ indicates memory location, where XX is a number from 01 to 20. For example: A03 indicates memory address 03 is in use. 3. Error Codes ÒEXXÓ where XX = a number. For example: E11 indicates a calibration error. See the troubleshooting section of this manual for details on error codes. Temperature Display The small digits display temperature in o C. The display is accurate only when he probe is in solution. The temperature sensor is can be calibrated by the user ( See Page 24). AUTO HOLD (eye icon) Indicator This mode allows a reading to remain automatically locked on the display for future reference. The eye symbol indicates that the meter is in the automatic hold ÒAUTO HOLDÓ mode. The eye symbol starts flashing when the meter begins to take a reading and stops flashing (locks) when the reading has stabilized. The reading remains locked until the ph key is pressed to unlock he reading or the HOLD key is pressed to exit the AUTO HOLD mode. 6

7 Meter Connections RS-232 Standard 9 pin connector for serial output to printer or computer. AC Power Adapter to attach the provided AC adapter. Analog Recorder Output for a chart recorder. Probe Connector Jack for connection of ph probe to meter. Status Indicators ph mv REL mv BUFFER Indicates that the meter is in the ph mode. Flashing ph arrow indicates that the meter is still seeking a stable reading. Stable ph arrow indicates that a stable reading ÒendpointÓ has been reached. Indicates that the meter is in the Millivolt mode. Indicates that the meter is in the Relative Millivolt mode. Indicates that the meter is in the Select Buffer mode. 1 PT Indicates that one buffer value has been used for calibration. If flashing, first buffer has been selected but not read. 7

8 2 PT Indicates that two buffer values have been used for calibration. If flashing, second buffer has been selected but not read. 3 PT Indicates that three buffer values have been used for calibration. If flashing, third buffer has been selected but not read. RECALL STORE PROBE Battery icon Indicates that the meter is in Memory Recall mode. Indicates that the meter is in Memory Storage mode. Indicates damaged probe and/or calibration problem. Indicates meter is on battery power. Flashing indicates battery should be replaced. 8

9 Keypad Functions ON/OFF CLEAR ph Turns meter ON and OFF. When turned off, the meter retains the calibration in memory. If the meter is on battery power and no key is pressed for 10 hours, the meter will turn off automatically. If the meter is operating on battery power and an error message is displayed for 10 minutes, the meter will turn off automatically. If the meter is operating on AC power, it will not turn off automatically. Used to clear the meter of the current value. This key has various uses, as described in these instructions. Selects ph mode..1/.01/.001 Selects the resolution of the ph reading. mv Selects the mv mode. When pressed successively, toggles between mv and the Relative mv mode. 9

10 SELECT CAL HOLD STORE ENTER Selects the Select Buffer mode. Repeatedly pressing the SELECT BUFFER key scrolls through Automatic Buffer Recognition values. Selects the Calibration mode. Selects the Auto Hold mode. When Auto Hold mode is ON, the eye symbol is displayed. When a stable reading is obtained, the display remains locked until the ph key is pressed or the HOLD key is pressed to turn off the Auto Hold function Selects the Memory Storage mode. Pressing a second time selects the Memory Recall mode. Used to increment through memory addresses or manually set buffer values. Various functions depending upon the mode. Generally used to store information (calibrations and sample readings) and to send data to the serial port. 10

11 Cleaning and Reconditioning ISFET Probes Cleaning With Detergent Regularly clean the ISFET probe with detergent (a few drops of dish detergent in a cup of warm water). Rinse well with deionized water. ISFET probes can be cleaned with a toothbrush and detergent Reconditioning with Warm Buffer ISFET probes are designed to be stored dry and have a virtually unlimited shelf life; however extended period of dry storage can crystallize the KCl gel at the reference junction. Heat ph 7.00 buffer to approximately 45 o C (115 o F). Soak the probe for 2 minutes. Place the probe in room temperature ph 7.00 buffer and allow to cool. CAUTION: Do not use the probe as a thermometer to determine if the buffer is above 60 o C. Sudden immersion in excessively hot water may permanently damage the probe. 11

12 Cleaning With Alcohol or Methanol The ISFET sensor (recessed shiny blue-green spot at the probe tip) can be gently cleaned using alcohol or methanol and a wooden toothpick tipped with a small amount of cotton wool. Be sure that the cotton tip is small enough to actually make contact with the recessed sensor. CAUTION: Do not use metal objects such a pins or paperclips to clean the sensor. The sensor can be permanently damaged with aggressive abrasion of the sensor surface. Cleaning with Sodium Hypochlorite (Bleach) If the ISFET probe has been exposed to fat or protein, the response time may begin to slow. Soak the probe for five minutes in a 10:1 dilution of deionized water to household bleach (0.5% solution of sodium hypochlorite). Brush with a soft bristle brush or toothbrush to remove deposits. The sensor is slightly recessed, be sure to make gentle contact with the sensor surface. Rinse well with deionized water. CAUTION: Do not soak the probe in sodium hypochlorite for more than 5 minutes. Extended immersion will permanently damage the probe. 12

13 ph Calibration and Measurement Range The IQ240 can measure from ph 0 to 14. Temperature compensation is automatic from -5 o C to + 80 o C. The meter can perform a one, two or three point calibration using any buffer listed below. Calibration Buffer Options 1.68, 4.00, 6.86, 7.00, 7.41, 9.18, 10.01, and Important Notes for Best Calibration Results It is recommended to avoid temperatures above 60 o C (140 o F) when possible. Elevated temperatures shorten the life of ph probes. Always clear the previous calibration before beginning the calibration procedure (See Step 6 of ÒCalibration with Two BuffersÓ on Page 14). Always begin each measuring session with a two-point calibration. Calibrate no greater than 3 ph units apart. If probe is new or has not been in regular use, soaking the probe in ph 7.00 buffer for at least five minutes is recommended. For best accuracy, when working at non-ambient temperatures, allow the probe to equilibrate to the temperature of the buffer or sample solution before starting calibration or ph measurement. Erroneous results will occur if the meter is incorrectly calibrated; for example, setting the Buffer Value to ph 7.00 when the probe is in ph 4.00 buffer. If unusual behavior occurs, recheck the buffer values, clear the previous calibration, and recalibrate the meter. If calibration times are excessive (over 2 minutes) follow the cleaning and reconditioning instructions on Page 11. Optimizing for Accuracy or Response Time The normal operating resolution is 0.01 ph. You can change resolution by pressing the.1/.01/.001 key to optimize for accuracy or response time. Use ph resolution for maximum accuracy. Use 0.1 ph resolution to optimize for maximum speed; the response time in 0.1 resolution will be approximately three times the speed of resolution. 13

14 Calibration with Two Buffers 14 Remember: Always use buffers that bracket the sample ph range. (For example, if the sample is about 8.5, use 7.00 and buffers). The narrowest calibration range gives the most accurate reading. 1. Remove black protective cap from probe tip and connect probe to meter. A small amount of clear or blue gel may be visible at the probe tip. 2. If probe has not been in regular use, hydrate the probe for five minutes in ph 7.00 buffer. 3. Place probe in the first buffer solution. Stir briefly to remove any bubbles from the probe surface. 4. Press ON/OFF to turn on meter. 5. The ph status indicator arrow (top left corner of LCD display) should be pointing to ph. If not, press the ph button until the status indicator points to ph. The BUFFER status indicator should NOT be displayed. 6. Press CAL then CLEAR to clear previous calibration. 7. Meter will automatically identify the ph of the first buffer solution. If the display does not match the ph of the buffer, press SELECT BUFFER until display matches the first buffer solution ph. The 1 PT status indicator arrow will be flashing. (If using a buffer other than those automatically recognized by the IQ240, refer to Page 17, Changing Stored Automatic Buffer Recognition Values). 8. Press ENTER. The buffer ph value will begin flashing to indicate calibration is underway. Wait until the buffer ph value and 1 PT status indicator arrow stop flashing. NOTE: When calibration is complete, the ph reading displayed will be the automatically temperature compensated (ATC) ph value of the buffer (e.g. ph 7.00 buffer will be corrected to 7.01 if the buffer is at 20 o C, ph buffer will be corrected to at 20 o C). 9. Rinse probe in deionized water and place in the second buffer. Stir briefly to remove any bubbles from the sensor surface.

15 10. Press CAL. 11. Meter will automatically identify the ph of the second buffer solution. If the display does not match the ph of the buffer, press SELECT BUFFER until display matches the second buffer solution ph. The 2 PT status indicator arrow will be flashing. 12. Press ENTER. The ph buffer value will begin flashing to indicate calibration is underway. Wait until the ph buffer value and 2 PT status indicator arrow stop flashing. 13. When the ph buffer value stops flashing, two point calibration is complete. 14. Rinse probe in deionized water and place in sample. Read sample ph. Calibration with Three Buffers Three point calibration is the most accurate method of ph measurement, especially if the samples cover a wider range. Use buffers that bracket the sample ph range. The narrowest range gives the most accurate readings. 1. Follow steps 1 through 13 of the ÒCalibration with Two BuffersÓ procedure. 2. Rinse probe in deionized water and place in the third buffer. Stir briefly to remove any bubbles from the sensor surface. 3. Press CAL. 4. Meter will automatically identify the ph of the third buffer solution. If the display does not match the ph of the buffer, press SELECT BUFFER until display matches the third buffer solution ph. The 3 PT status indicator arrow will be flashing. 5. Press ENTER. The ph buffer value will begin flashing to indicate calibration is underway. Wait until the ph buffer value and 3 PT status indicator arrow stop flashing. 6. When the ph buffer value stops flashing, three point calibration is complete. 7. Rinse probe in deionized water and place in sample. Read sample ph. 15

16 Calibration with One Buffer One point calibration is recommended only if the sample ph is very close to the calibration buffer ph and an accuracy of ±0.1 ph is acceptable. 1. Follow steps 1 through 8 of the ÒCalibration With Two BuffersÓ procedure. 2. Rinse probe in deionized water and place in sample. Read sample ph. How to Abort Calibration If calibration times are excessive (ph buffer value continues to flash) or you wish to stop during calibration for any other reason, press CLEAR then ph. The meter will enter the ph reading mode. If no previous calibration is in memory, an error code (E10 or E11) may result. Please refer to the Troubleshooting Tips on Page 26 and the Cleaning and Reconditioning Instructions on Page 11 if trouble is experienced in calibration. Automatic Buffer Recognition Auto Buffer Recognition can discriminate between buffers that differ by more han 0.5 ph units. However, closely lying buffers (such as 6.86, 7.00 and 7.41) may not be selected correctly. The IQ240 has storage locations for nine buffer values. The factory default values are 1.68, 4.00, 6.86, 7.00, 7.41, 9.18, 10.01, 11.88, If the Automatic Buffer Recognition selects the wrong buffer during calibration, press SELECT BUFFER to select the correct buffer value. Then press ENTER to start the calibration. The user can replace any or all of the factory default values with custom buffer values in ncrements of 0.01 ph. (See Page 17). 16

17 Automatic Temperature Compensation of Automatic Buffer Recognition Values Factory default Automatic Buffer Recognition values have temperature correction data stored in the meter. The meter displays the nominal buffer value at 25 o C. When the calibration is complete, the meter performs the automatic temperature compensation for the actual temperature of the buffer being used (e.g. ph 7.00 buffer will be corrected to 7.01 if the buffer is at 20 o C, ph buffer will be corrected to at 20 o C). The meter does not perform temperature compensation on buffer values input by the user since temperature correction tables are not available. When user-entered buffer values are displayed, the temperature display shows a flashing temperature. The table below shows the ph values of buffers at various temperatures. Nominal Value 25 o C 0 o C 5 o C 10 o C 20 o C 30 o C 40 o C 50 o C Changing Stored Automatic Buffer Recognition Values To change the factory default buffer values: 1. Press SELECT BUFFER to scroll through the factory default values available. 2. To change any value, press the or keys. 3. Press ENTER to store this new value. NOTE: If a buffer value already exists in memory the error code ÒdUPÓ (duplicate) will be displayed. To clear the error, press the ph key. REMEMBER: User defined buffer values are not temperature compensated. 17

18 Restoring Factory Default Automatic Buffer Recognition Values. 1. Press SELECT BUFFER repeatedly to until the display shows the buffer value to be restored to the factory default value. 2. Press CLEAR to clear the displayed value. ÒClrÓ is displayed. 3. Press ENTER to restore the factory default value in memory. mv Measurement Absolute mv Measurement 1. Connect probe to meter. 2. Press ON/OFF to turn on meter. 3. Press mv to place meter in the mv mode. Be sure the status indicator is NOT pointing to ÒREL mvó. If necessary, press the mv key until the status indicator arrow points to ÒmVÓ. The display will show the current mv reading. NOTE: Repeatedly pressing mv toggles between the mv and Relative mv modes. The status indicator arrow indicates the current reading mode. When n the AUTO HOLD mode, a single press of the mv key starts a new reading. Relative mv Measurement During calibration in the mv mode, the meter takes a reading on a solution and sets its reading to mv. This solution becomes the standard. The calibration data is stored, so that all subsequent readings taken in the Relative mv mode are relative to the initial standard. 1. Connect probe to meter. 2. Press ON/OFF to turn on meter. 3. Press mv to place meter in the mv mode. Be sure the status indicator is NOT pointing to ÒREL mvó. If necessary, press the mv key until the status indicator arrow points to ÒmVÓ. The display will show the current mv reading. 18

19 4. Place probe in solution to be used as the standard. Stir briefly to remove any air bubbles. The mv reading of the solution will be displayed. 5. Press CAL. The mv value of the solution will be displayed and the flashing status indicator arrow will point to 1 PT. 6. Press ENTER. The mv value will flash until calibration is complete. Upon completion, the mv value will be set to and the mode will switch to Relative mv. 7. Rinse probe in deionized water and place in sample. The mv value displayed will be Relative mv to the standard. NOTE: The HOLD function is active in the mv and Relative mv mode. Press the mv key to release the display from a ÒlockedÓ reading. 19

20 Storing and Recalling Data The IQ240 can store and recall 20 sample readings (temperature and ph, mv or Relative mv) in memory for later recall. The memory storage addresses are labeled A01 to A20. Storing Sample Readings 1. Follow the instructions to display the desired ph or mv readings. 2. Press STORE/RECALL to put the meter in Store mode. The status indicator arrow points to ÒSTOREÓ. The next available memory storage address is displayed (AXX). 3. To access a different memory storage address, press the or key to scroll through the storage locations. 4. When the desired storage address is displayed, press ENTER to store the reading and temperature. As soon as the reading is stored, the meter returns to the reading mode. Recalling Sample Readings. 1. Press STORE/RECALL to place the meter in the Store mode. The status indicator arrow points to ÒSTOREÓ and the next available storage address is displayed. 2. Press STORE/RECALL again to place the meter in the Recall mode. The status indicator arrow points to ÒRECALLÓ. 3. Press the or keys to display the desired memory storage address. 4. Press ENTER to display the contents of the displayed address. If the storage address is empty, ÒClrÓ is displayed. 20

21 Clearing Data from One Storage Address 1. Press STORE/RECALL to place the meter in the Store mode. The status indicator arrow points to ÒSTOREÓ and the next available storage address is displayed. 2. Press STORE/RECALL again to place the meter in the Recall mode. The status indicator arrow points to ÒRECALLÓ. 3. Press the or keys to display the desired memory storage address. 4. Press CLEAR. The display reads ÒClrÓ. 5. Press ENTER to clear the storage address. Clearing Data from All Storage Addresses. 1. Press STORE/RECALL to place the meter in the Store mode. The status indicator arrow points to ÒSTOREÓ and the next available storage address is displayed. 2. Press STORE/RECALL again to place the meter in the Recall mode. The status indicator arrow points to ÒRECALLÓ. 3. Press and hold down the CLEAR key and press the ENTER key. The display reads ÒClrAllÓ. All memory storage addresses are cleared. 21

22 Output Modes Analog Output An analog signal is sent to the recorder output continuously whenever the meter is in a reading mode. The output is 0.00 mv at ph 7.00 with a slope of mv/ph over the range of 0 to 14 ph. The analog output is temperature compensated for the temperature of the sensor. To connect the analog recorder to the meter, a cable with a miniature phono jack is required. Serial Output To connect to the serial port on the meter, use a NULL MODEM cable less han 3 meters long, with a 9-pin DB-9 connector. Data are sent to the serial port using the following criteria: There are a maximum of 20 characters per line Each line ends with a carriage return and a line feed. When the transmission is complete a second line feed is sent. The baud rate is user selectable to 300, 1200 or The meter sends 8 bit data, no parity, and one stop bit. NOTE: The use of the serial port can quickly drain the battery. It is recommended that the AC adapter be used whenever the meter is connected to a serial device. To limit the possibility of unintentional battery depletion when the meter is operating on battery power, the serial port is only active (momentarily) when the ENTER key is pressed. The serial port is always active when the AC power adapter is used. Some serial devices require that the serial port be continuously active. For hese devices, the ÒmomentaryÓ feature can be overridden by simultaneously pressing the key and the CLEAR keys. The override is indicated by a flashing battery symbol (similar to a low battery condition). The override is canceled when the meter is turned off. Only use this override if problems with serial communications (such as garbled data, are experienced). Since a mismatch of serial port settings can also cause garbled data transfer, make sure that the meter and the external device are set to the same baud rate; along with 8 data bits, no parity, and 1 stop bit. Recheck the setting before using the override. 22

23 Output the Calibration Data to the Serial Port 1. The calibration data will be automatically sent to the serial port at the end of the calibration process when the ph buffer value stops flashing. Output the Current Sample Reading to the Serial Port 1. With the reading displayed, press ENTER. Any error message(s) related to the reading will also be printed following the reading. Output the Contents of a Single Memory Address to the Serial Port 1. Display the desired memory storage address using the directions on Page Press ENTER to display the contents of the storage address and simultaneously send the data to the serial port. Output the Contents of All Memory Addresses to the Serial Port 1. Press STORE/RECALL to place the meter in the Store mode. The status indicator arrow points to ÒSTOREÓ and the next available storage address is displayed. 2. Press STORE/RECALL again to place the meter in the Recall mode. The status indicator arrow points to ÒRECALLÓ. 3. Press and hold down STORE/RECALL and press ENTER. NOTE: Only memory storage addresses containing data are sent to the serial port. Setting the Baud Rate 1. Press and hold down the key and press the.1/.01/.001 key to enter the baud rate selection mode. The current baud rate is displayed. 2. Press the key to cycle between 300, 1200, and The factory default baud rate is When the desired baud rate is displayed, press ENTER. The meter stores the new baud rate and returns to its prior mode. 23

24 Temperature Calibration User Temperature Calibration Use the following procedure to calibrate the temperature sensor. NOTE: The Auto HOLD (Auto eye icon) must be off during temperature calibration. 1. Immerse the probe in a solution of known temperature. 2. Press and hold down the key and press CAL. The meter enters the temperature calibration mode. The temperature display flashes. 3. Press the or keys to set the temperature to the nearest 0.1 o C. Each time arrow key is pressed, the temperature is incremented in steps of 0.05 o C. Therefore, it is necessary to press the arrow key twice to see a 0.1 o C change on the display. 4. When the desired temperature is displayed, press ENTER. Restoring Temperature Calibration to Factory Default 1. Press and hold down the key and press CAL. The meter enters the temperature calibration mode. The temperature display flashes. 2. Press CLEAR, then ENTER. 24

25 Battery Replacement A 9v alkaline battery powers the IQ240 meter. The expected battery life is 200 hours of operation. The flashing status indicator arrow on the display indicates low battery voltage. Replace the battery whenever low voltage is indicated. Internal memory is not lost when the battery is replaced. To Replace the Battery: 1. Disconnect all connectors from the meter. 2. Turn the meter upside down. 3. Use a Phillips screwdriver to unscrew the two screws, located at the bottom of the two cylindrical cavities. 4. Carefully lift the bottom case of the meter directly up, allowing the screws to remain in the cavities. 5. Remove the old battery, and install the new battery. 6. Replace the cover and secure by tightening the two screws. 25

26 Troubleshooting INDICATION CAUSE USER ACTION No Display No Power Replace 9v battery, or use AC power adapter. Auto Power Off Press ON/OFF key. Battery status ndicator arrow flashing PROBE status ndicator arrow flashing Unstable reading, (ph status ndicator does not stop flashing). has cleared display Battery is low The meter is in the serial output override mode Probe not connected to meter Dirty probe/meter contacts. Damaged probe Dirty probe. Reference junction not flowing. Miscalibrated probe. Interference from other devices. Interference from direct sunlight. Probe is in a very low ionic strength solution. Follow the directions for battery replacement on Page 25. See Page 22. Check probe connection to meter. Disconnect probe, then reconnect probe to meter (An audible click indicates that the probe is in place). Clean probe contacts on probe cable connector and meter with methanol and a cotton swab and let dry completely. Reconnect probe to meter. If condition persists, replace probe. Follow probe cleaning procedure on Page 11. Follow warm buffer cleaning procedure on Page 11. Soak probe for three minutes in neutral buffer (ph 7.00). Follow two point calibration procedure on Page 14. Remove other devices from solution. Unplug water baths, stirrers, etc. If working outside, shield the probe from direct sunlight. Stable reading may not be possible. 26

27 Unstable reading, (ph status indicator does not stop flashing) Cont... Trouble calibrating. (ph buffer value does not stop flashing during calibration). ph or temperature of solution is changing. Probe near end of useful life. Low battery. Probe sensor surfaces are dirty or probe needs reconditioning. Reference junction not flowing. E10, E11 or E12 error message displayed. Improper calibration procedure. Buffers may be contaminated or expired. Interference from other devices in solution. Improperly grounded stirrers, water baths other devices. Battery is low. Interference from direct sunlight. If trouble persists, probe may have reached the end of its useful life and may need to be replaced. Display will show changes in ph values due to change in solution ph or temperature (meter is automatically temperature compensated to show actual ph at any given temperature). Replace probe. Replace battery if battery status indicator arrow is flashing. Follow cleaning and reconditioning instructions on Page 11. Follow warm buffer cleaning procedure on Page 7. Follow troubleshooting instructions on Page 28. Carefully follow Two Point Calibration procedure on Page 14. Recalibrate with fresh buffers. Remove any other devices from solution. Unplug water baths, stirrers, or any other electrical devices near the probe. Use AC adapter or replace battery if low battery indicator is flashing. Shield probe from sunlight. Replace probe. 27

28 Error Codes INDICATION CAUSE USER ACTION E01 This error code is displayed after the meter is turned on if any malfunction is detected. Turn the meter off. Disconnect, then reconnect the probe. Disconnect any cables connected to the RS-232 or analog ports. Turn the meter on. If E01 persists, and the meter is used with the AC power adapter, turn the meter off. Disconnect then reconnect the power adapter. Turn the meter on. If EO1 persists, turn the meter off. Disconnect the AC power adapter. Turn the meter on using battery power only. E10 This error code is displayed if a probe malfunction is detected, including probe not in solution. If EO1 persists replace probe. Probe may be dry. Place probe in solution. If E10 persists, follow the probe cleaning and reconditioning instructions in this manual. If the error code persists, turn the meter off. Disconnect, then reconnect to probe. Disconnect any cables connected to the RS-232 or analog ports. Turn the meter on. E11 This error code is displayed after completion of any calibration procedure which indicates an out of specification response slope (<45 mv/ph). If E10 persists, probe may have reached the end of its useful life. Replace probe. Carefully follow the two point calibration instructions using fresh buffers. If E11 persists, follow the probe cleaning and reconditioning instructions in this manual. If E11 persists, probe may have reached the end of its useful life. Replace probe. 28

29 Error Codes continued. E12 This error code is displayed after a calibration error. One common cause is the operator overriding the automatic buffer recognition with the SELECT BUFFER key and then selecting the wrong buffer value. Carefully follow the two point calibration instructions. Use extra caution to be sure that the correct buffer value is displayed before pressing the ENTER key to begin the calibration. If E12 persists, probe may have reached the end of its useful life. Replace probe. 29