IQ Scientific Instruments IQ240 User manual

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MODEL IQ240 pH Meter
Getting Started
TWO-POINT CALIBRATION--QUICK REFERENCE GUIDE
1. 2. 3. 4.
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.
5.
6. 7. 8.
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
deionized water and
place in second
calibrating buffer.
9. 10. 11. 12.
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
deionized water and
place in sample.

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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 “3-in-1” 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 that
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.

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Table of Contents
Getting Started--
Quick Reference Guide for Two Point Calibration. . . . . . .
1
Techniques and Tips For Best Performance. . . . . . . . . . . . . . . . . . . . . . 4
Display Features and Meter Connections. . . . . . . . . . . . . . . . . . . . . . . . 6
Main Display. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Meter Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Status Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Keypad Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Cleaning and Reconditioning the Probe. . . . . . . . . . . . . . . . . . . . . . . . . 11
pH Calibration and Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Important Notes for Best Calibration Results. . . . . . . . . . . . . . . . . . . 13
Calibration With Two Buffers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Calibration With Three Buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Calibration With One Buffer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
How to AbortCalibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Automatic Buffer Recognition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Automatic Temperature Compensation of Automatic Buffer
Recognition Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Changing Stored Automatic Buffer Recognition Values. . . . . . . . . . 17
Restoring Automatic Buffer Recognition Values to Factory Default. 18
mV Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Titrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storing and Recalling Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 20
Storing Sample Readings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Recalling Sample Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Clearing Data from One Storage Address. . . . . . . . . . . . . . . . . . . . . . 21
Clearing Data from All Storage Addresses. . . . . . . . . . . . . . . . . . . . . 21
Output Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
AnalogOutput. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Serial Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Output of Calibration Data to the Serial Port. . . . . . . . . . . . . . . . . . . 23
Output of Current Sample to the Serial Port. . . . . . . . . . . . . . . . . . . . 23
Output of the Contents of a Single Memory Address . . . . . . . . . . . . 23
Output of the Contents of all Memory Addresses . . . . . . . . . . . . . . . 23
Setting the Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Temperature Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
User Temperature Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Restoring Temperature Calibration to Factory Default. . . . . . . . . . . 24
Battery Replacement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Error Codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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Techniques and Tips for Best Performance
DO
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
the sensor surface.
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
the 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).

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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. Call IQ Scientific Instruments or your
Authorized Dealer for optional light shields.
DO NOT: use the probe in an environment that will damage the 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 the probe in environments with static electricity. Electrostatic
discharge may permanently damage the probe.
DO NOT: expose the ISFET probe to repeated temperature extremes (60 oC or
higher). Do not use the probe for applications that require the probe to cycle
between hot and room temperature samples.
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.

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Display Features and Meter Connections
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 “AXX” 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 “EXX” 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 oC. The display is accurate only when
the probe is in solution. The temperature sensor 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 “AUTO HOLD” 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
the reading or the HOLD key is pressed to exit the AUTO HOLD mode.

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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.
pH 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
“endpoint” has been reached.
mV Indicates that the meter is in the Millivolt mode.
REL mV Indicates that the meter is in the Relative Millivolt
mode.
BUFFER 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.

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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 Indicates that the meter is in Memory Recall mode.
STORE Indicates that the meter is in Memory Storage mode.
PROBE Indicates damaged probe and/or calibration problem.
Indicates meter is on battery power. Flashing indicates
battery should be replaced.

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Keypad Functions
ON/OFF 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.
CLEARUsed to clear the meter of the current value. This
key has various uses, as described in these
instructions.
pH 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.

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SELECT Selects the Select Buffer mode. Repeatedly pressing
the SELECT BUFFER key scrolls through
Automatic Buffer Recognition values.
CAL Selects the Calibration mode.
HOLD 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
STORE 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.
ENTER Various functions depending upon the mode.
Generally used to store information (calibrations and
sample readings) and to send data to the serial port.

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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 oC and
60 °C (115 oF and 140 °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 oC. Sudden immersion
in excessively hot water may permanently damage the
probe.

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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: Cleaning with alcohol is not
recommended if the sample you are testing contains
proteins. Use Sodium Hypochlorite (see below).
CAUTION: Do not use metal objects such as 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.

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pH Calibration and Measurement
Range
The IQ240 can measure from pH 0 to 14. Temperature compensation is
automatic from -5 oC to + 80 oC. 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, 11.88 and 12.45.
It is recommended to avoid temperatures above 60oC
(140 oF) when possible. Elevated temperatures
shorten the life of pH probes.
Important Notes for Best Calibration Results
•Always clear the previous calibration before beginning the calibration
procedure (See Step 6 of “Calibration with Two Buffers” 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
0.001 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 0.001 resolution.

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Calibration with Two Buffers
Remember: Always use buffers that bracket the sample pH
range. (For example, if the sample is about 8.5, use 7.00 and
10.01 buffers). The narrowest calibration range gives the
most accurate reading.
1. Remove the black protective cap from the probe tip and connect the
probe to the meter. A small amount of clear or blue gel may be visible
at the probe tip.
2. If the probe has not been in regular use, hydrate the probe for five
minutes in pH 7.00 buffer.
3. Place the probe in the first buffer solution. Stir briefly to remove any
bubbles from the probe surface.
4. Press ON/OFF to turn on the meter.
5. The pH status indicator arrow (top left corner of the 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. The 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 the 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 20oC, pH 10.01 buffer will be corrected to 10.06
at 20 oC).

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9. Rinse the probe in deionized water and place in the second buffer. Stir
briefly to remove any bubbles from the sensor surface.
10. Press CAL.
11. The 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 the 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 “Calibration with Two Buffers”
procedure.
2. Rinse the probe in deionized water and place in the third buffer. Stir
briefly to remove any bubbles from the sensor surface.
3. Press CAL.
4. The 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.

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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 “Calibration With Two Buffers”
procedure.
2. Rinse the 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
than 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, 12.45. 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
increments of 0.01 pH. (See Page 17).

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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 oC. 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 oC, pH 10.01 buffer will be corrected to 10.06 at 20 oC). 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 oC0oC5oC10oC20oC30oC40oC50oC
1.68 1.67 1.67 1.67 1.67 1.68 1.69 1.71
4.00 4.00 4.00 4.00 4.00 4.01 4.03 4.06
6.86 6.98 6.95 6.92 6.87 6.85 6.84 6.83
7.00 7.12 7.09 7.06 7.01 6.99 6.97 6.97
9.18 9.46 9.40 9.33 9.23 9.14 9.07 9.02
10.01 10.32 10.25 10.18 10.06 9.97 9.89 9.83
12.45 13.42 13.21 13.00 12.63 12.29 12.04 11.70
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 “dUP”(duplicate) will
be displayed. To clear the error, press the pH key.
REMEMBER: User defined buffer values are not
temperature compensated.