LaMotte pHPLUS DIRECT User manual

Instruction Manual
pHPLUS DIRECT
pH/mV/ISE Meter
Code 5-1936

PREFACE
This instruction manual serves to explain the use of the pHPLUS DIRECT
meter.
It functions in two ways: first as a step by step guide to help you operate the
meter; second, it serves as a handy reference guide.
This manual is written to cover as many anticipated applications of the
pHPLUS DIRECT meter as possible. If there are doubts in the use of this
meter, please do not hesitate to contact the LaMotte Tech Service
Department.
LaMotte will not accept any responsibility for damage or malfunction to the
meter caused by improper use of the instrument.
The information presented in this manual is subject to change without notice
as improvements are made, and does not represent a commitment on the part
of LaMotte Company.
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Table of Contents
1. Introduction ............................. 5
2. Getting Started ........................... 6
2.1 Description of Keypad Functions ................... 6
2.2 Description of LCD Annunciations ................. 7
2.3 Inserting & Removing the Rubber Boot ............... 7
2.4 Inserting New Batteries ........................ 8
2.5 Battery Replacement ......................... 8
2.6 Connecting the Electrode and Temperature Sensor .........8
2.7 Condition the pH Electrode ..................... 9
2.8 Switching the Meter On ....................... 9
3. Calibration ............................. 10
3.1 pH Calibration............................ 10
3.2 Selection of pH buffer standards .................. 11
3.2.1 Resetting the User Calibrated Values ............... 11
3.2.2 pH Calibration using USA standard buffers ...........12
3.2.3 pH Calibration using NIST standaard buffers ...........13
3.2.4 pH Calibration using Pb Standard buffers ............14
3.3 Ion Calibration ........................... 15
3.3.1 Multi-point Ion Calibration ................... 16
3.4 Temperature Calibration ...................... 17
3.4.1 With Temperature probe .................... 17
3.4.2 Without Temperature probe (no ATC) .............18
4. Measurement ............................ 19
4.1 Taking Measurements ........................ 19
4.2 Millivolt (mV) Reference Check .................. 19
4.3 Holding a Reading .......................... 19
4.4 Releasing a Held Reading ...................... 19
5. Electrode Care and Maintenance .................20
6. Troubleshooting .......................... 20
7. Specifications ........................... 21
8. Accessories ............................. 22
9. Warranty Information ..................... 22-23
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1. INTRODUCTION
Thank you for purchasing the pHPLUS DIRECT meter. This
microprocessor-based handheld meter is economical and easy to use. It has a
large custom LCD (Liquid Crystal Display) for clear and easy reading.
The pHPLUS DIRECT measures pH, mV (ORP), temperature and ion
concentration of various ions (mono and di valence) with ion selective
electrodes (ISEs).
Included with your meter are a robust rubber boot, 4 alkaline “AAA” batteries,
buffer solutions, accessories, temperature sensor, instruction manual and a
warranty card. To order other accessories and buffer calibration or standard
solutions, please refer to Section 8 on Accessories for more information.
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2. GETTING STARTED
2.1 Description of Keypad Functions
The pHPLUS DIRECT has six keys on its splash-proof keypad with tactile
feedback. The keys include ON/OFF,HOLD/ENTER,CAL,MODE,p
and qkeys.
Powers meter on and off. Meter starts up in the mode that you were in
before turning the meter off.
Selects measurement mode for Ion, mV, pH and Temperature.
Allows calibration for Ion, pH, mV or Temperature, or to abort
calibration without confirming any set value.
Allows you to increase values during calibration mode.
Allows you to decrease values during calibration mode.
Freezes the measured reading for easy viewing.
Confirms calibration value.
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CAL
MODE
ON
OFF
HOLD
ENTER
ON
OFF
CAL
HOLD
ENTER
HOLD
ENTER
MODE

2.2 Description of LCD Annunciators
The meter has a large custom LCD that consists of 3½-digit segments and
operation annunciators for pH, mV or °C (Temperature). Note that there is no
annunciator shown in the Ion mode. Other annunciators include “HO” (when
the HOLD function is activated) and “LO” (low battery condition).
2.3 Inserting & Removing the Rubber Boot
1. To remove the meter from the rubber boot, push out the bottom edges of
the meter until it is completely out of the boot. Ensure that the cables of
the ISE/pH electrode or temperature probe are not connected
2. To insert the meter into the rubber boot, slide the top of the meter into the
boot before pushing the bottom edge of the meter down to set it into
position. Lift up the stand on the back of the meter for bench top
applications if desired.
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2.4 Inserting New Batteries
The battery compartment is found at the back of the instrument. To open the
battery compartment, push in the direction of the arrow and lift up the cover.
Note the polarity of the batteries before inserting them into position. After
replacement, replace the cover and press down until it locks tight.
2.5 Battery Replacement
A“LO” annunciator in the LCD alerts you when battery power is running low.
Replace the batteries with the type recommended by the manufacturer.
Caution: Power off the meter when changing the batteries.
2.6 Connecting the Electrode and Temperature Sensor
To connect the electrode to the meter, align the connector slots with the posts
of the meter socket and rotate the connector clockwise until it locks. Do not
force it when connecting. To remove the electrode, simply rotate the
connector in a counterclockwise direction until it unlocks, and slide the
connector off the socket.
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Insert the mini phono jack of the temperature sensor into the socket on the
meter. Unplug the phono jack when not in use or when pH is being measured
without any temperature compensation.
2.7 Condition the pH Electrode
Condition the pH electrode before the first use or if it has not been in use for a
long time by soaking it in a container filled with pH 4 buffer solution for at
least 1 hour. Rinse with tap water before proceeding.
2.8 Switching the Meter On
1. Press the ON/OFF key to power up the meter. All LCD segments will be
displayed momentarily as the meter performs a self-diagnostic test, as
shown in section 2.2. The meter will be in the Ion measurements mode if
the meter has not been calibrated or reset. The display will show "---".
2. Press the MODE key to choose the desired mode of measurement, The
corresponding annunciator will be displayed on the LCD. In the
temperature mode, the display will show 25°C (factory default), the last
calibrated temperature if there is no temperature probe connected, or the
current measurement value if a temperature probe is connected.
3. The display will show “Ur” if the measurement is under the minimum
measurement or “Or”if the measurement is over the maximum
measurement range.
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Phono jack of
Temperature probe
BNC of pH/ORP
Electrode or ISE

3. CALIBRATION
3.1 pH Calibration
The meter is capable of calibrating up to 3 points using USA or NIST (nSt)
pH buffer standards or 2 points with Low Ionic (Pb) pH buffer standards. All
new calibration values will automatically override existing data.
USA pH 4.01,7.00 and 10.01
NIST pH 4.01, 6.86 and 9.18
Pb pH 4.10 and 6.97
It is recommended that you perform at least a 2-point calibration at room
temperature (25 °C) using standard buffers, starting with the first buffer at pH
7.00 (USA), pH 6.86 (NIST) or pH 6.97 (Pb) followed by other buffer values.
For a 1-point calibration, the calibration should be performed with a pH buffer
value closest to the expected sample value being measured. Otherwise
calibrating at pH 7.00, pH 6.86 or pH 6.97 is advisable.
The meter has automatic buffer recognition that identifies the correct pH
buffer values during calibration. If non-standard pH buffers other than the
above standards are used, or the electrode has worn out, the LCD will flash
“Er1”. Press the CAL key to abort calibration and resume measurement. In
general all pH buffer values have the window of up to +/- 1 pH tolerance
during calibration.
Ensure that you use new pH buffer solutions during calibration. Do not reuse
buffer solutions as they may be contaminated and affect the calibration and
accuracy of measurements. Always store buffer solutions in a dry, cool
environment if possible.
Before use, remove the plastic protective cap on the pH electrode and
condition the glass bulb by soaking it in tap water for 1-2 hours. This hydrates
the glass bulb if the electrode is too dry or has not been used for a long period
of time. Always rinse the probes with tap water or rinse solution before and
after each calibration/sample measurement to avoid cross-contamination. For
details refer to section 5 on Electrode care and maintenance.
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3.2 Selection of pH Buffer Standards
You must set the meter to accept either USA, NIST (nSt) or Low Ionic (Pb)
pH buffer standard values before calibration. The factory default is USA
standard. If you wish to abort this operation press the CAL key at any sequence
and the meter reverts to pH measurement mode.
1. Press and hold the MODE key. Switch on the meter using ON key. The
display shows “bUF” blinking.
2. Press the ENTER key to get into the buffer selection mode. Use the
MODE key to toggle between USA, NIST or Pb standards as shown.
3. Press the ENTER key to confirm the buffer standards to be used. The
display then reverts to pH measurement mode.
3.2.1 Resetting the User Calibrated Values
Note: only the temperature offset (if set) will not be erased.
1. Press and hold the CAL key while switching on the meter using the ON
key. The LCD shows “rSt” blinking.
2. Press the MODE key to abort this operation if you do not wish to reset
3. Press the ENTER key to confirm. The meter automatically clears all stored
pH/Ion calibration or mV offset values and reverts to measurement mode.
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3.2.2 pH Calibration using USA standard buffers
1. Pour a known pH buffer standard solution into a clean, dry container, e.g.
pH 7.00. Power on the meter and it will automatically enter the
measurement mode. Select the pH mode by pressing the MODE key if
necessary.
2. Dip both the pH electrode and temperature probes into pH 7.00 buffer
solution. Swirl gently and wait for the reading to stabilize (approx. 30
seconds depending on the electrode condition).
3. Press the CAL key to enter the pH calibration mode. “CA” will be displayed
momentarily and the display will flash with the current uncalibrated
reading.
4. To abort or cancel the calibration without accepting the new value, press
the CAL key. The meter then reverts to the pH measurement mode.
5. To proceed with the calibration, allow the reading to stabilize. The meter
will automatically recognize pH 4.01, 7.00 or 10.01 buffers. Press the
ENTER key to confirm the calibration and the LCD will display “CO”
momentarily. The meter will revert to the measurement mode.
6. Fora2or3-point calibration, repeat step 3 with other pH buffer values of
4.01 and/or 10.01 for higher accuracy.
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3.2.3 pH Calibration using NIST standard buffers
1. Pour a known pH buffer standard solution into a clean container, e.g. pH
6.86. Power on meter, and it will automatically enter the measurement
mode. Select the pH mode by pressing the MODE key if necessary.
2. Dip both the pH electrode and temperature probes into the pH 6.86 buffer
solution. Swirl gently and wait for reading to stabilize (approx. 30 seconds
depending on the electrode condition).
3. Press the CAL key to enter the pH calibration mode. “CA” will be displayed
momentarily and the display will flash with the current uncalibrated
reading.
4. To abort or cancel the calibration without accepting the new value, press
the CAL key. The meter then reverts to the pH measurement mode.
5. To proceed with the calibration, allow the reading to stabilize. The meter
automatically recognizes pH 4.01, 6.86 or 9.18 buffers. Press the ENTER
key to confirm the calibration and the LCD will display “CO” momentarily.
The meter will revert to the measurement mode.
6. Fora2or3-point calibration, repeat step 3 with other pH buffer values of
4.01 and/or 9.18 for higher accuracy.
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3.2.4 pH Calibration using Pb standard buffers
1. Pour a known pH buffer standard solution into a clean container, e.g. pH
6.97. Power on meter, and it will automatically enter the measurement
mode. Select the pH mode by pressing the MODE key if necessary
2. Dip both the pH electrode and temperature probes into the pH 6.97 buffer
solution. Swirl gently and wait for the reading to stabilize (approx. 30
seconds depending on the electrode condition).
3. Press the CAL key to enter the pH calibration mode. “CA” will be displayed
momentarily and the display will flash the current uncalibrated reading.
4. To abort or cancel the calibration without accepting the new value, press
the CAL key. The meter then reverts to the pH measurement mode.
5. To proceed with the calibration, allow the reading to stabilize. The meter
will automatically recognize either pH 4.10 or 6.97 buffer. Press the
ENTER key to confirm the calibration and the LCD will display “CO”
momentarily. The meter will revert to the measurement mode.
6. For a 2-point calibration, repeat step 3 with pH 4.10 buffer for better
accuracy.
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3.3 Ion Calibration
The pHPLUS DIRECT meter is capable of up to 3-point ion calibration
(minimum 2 point) with standard solutions to ensure accuracy across the
entire range of the meter.
To exit calibration after you have first entered into ion calibration, press the
CAL key again. No ion calibration values are stored into the meter’s
non-volatile memory. Note that ion calibration data is lost once the meter is
reset when the batteries are removed and replaced.
If one calibration point is performed an error message “Er2” will be displayed
after the single point calibration is completed. Recalibrate using a minimum of
2 points.
Calibration values are successfully stored if the ISE (Ion Selective Electrode)
slope is within the specified tolerance of 15-90 mV/decade, otherwise an error
message “Er3” is displayed.
If any of the calibration points are not within 1 decade, an error message “Er4”
will be shown at the end of calibration process. The ion calibration options
available include 0.1, 1.0, 10.0, 100.0 ppm. Recalibrate and ensure that all
calibration points must be at least 1 decade apart from each other.
Ensure that you use new or fresh standard solutions during calibration. Do not
reuse ion standard solutions as they may be contaminated and affect the
calibration and accuracy of measurements. Always store standard solutions in a
dry, cool environment if possible. Check that the ISE and ion standard
solutions are kept in good condition, otherwise erroneous readings may be
taken.
Before use, remove the plastic protective cap if present on the ISE (at the tip
of sensor) and read the manufacturer’s instructional manual. Briefly rinse the
electrode with clean deionized water to remove any residue.
Rinse probes before and after each calibration or sample measurement to avoid
cross-contamination. For more details please refer to Manufacturer’s care and
maintenance guide.
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3.3.1 Multi-point Ion Calibration
1. If a calibration with a 1.0 ppm standard is desired, the 0.1 ppm calibration
can be skipped (see below*).
2. For instance if a 1.0 ppm calibration standard is used, pour a known 1.0
ppm standard solution into a clean container. Power on the meter, and set
the meter to Ion measurement mode.
3. Dip the ISE into the 1.0 ppm standard solution. Stir it gently. Press CAL
key to enter into calibration mode.
4. The display shows “CA” momentarily followed by “0.1” flashing.
* If you wish to calibrate with a standard other than 0.1 ppm, press qkey
once to select 1.0 ppm. Use the por qkey to select other options like 0.1,
10.0 or 100.0 ppm.
5. Press the ENTER key and the displayed value will show the corresponding
measured mV reading that is equivalent to 1.0 ppm. Allow the reading to
stabilize.
6. Press the ENTER key to confirm the first calibration point (e.g. 1.0 ppm).
The display will show the next calibration option, 10.0 ppm. Rinse the
electrode with distilled water and blot it dry if necessary.
7. Pour a known 10.0 ppm standard solution into another clean container.
Dip the electrode into the standard solution. Stir it gently.
8. Press the ENTER key and the displayed value will show the measured mV
reading that is equivalent to 10.0 ppm. Allow the reading to stabilize.
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9. Press the ENTER key to confirm the second calibration point (e.g. 10.0
ppm). The display will show the next calibration option, 100.0 ppm.
To exit from the 2-point calibration, press the CAL key. The LCD will show
“PXX mV” momentarily which is the ISE slope in mV value.
The meter then reverts to ion measurement mode. The calibration values are
successfully stored into the memory. Otherwise an error message “Er3” will be
displayed if the slope of ISE is lower than 15mV/decade or higher than
90mV/decade.
10. For a 3-point calibration when the LCD shows “100.0”, press the ENTER
key to proceed to last calibration point. Repeat the above procedure.
At the end of the 3 point calibration the meter will display the mV slope of
the electrode as “PXX” and the calibration values will be successfully stored.
Error messages will appear in the LCD if the calibration was unsuccessful with
no values stored into memory.
3.4 TEMPERATURE CALIBRATION
3.4.1 With Temperature probe
The temperature probe provided with the meter is factory-calibrated. Over
time, temperature calibration may drift and require calibration. If there is a
need to replace the probe the temperature probe should be calibrated prior to
pH calibration.
1. Connect the temperature probe to the meter. Press the MODE key to
enter the Temperature mode until “°C” annunciator appears on the LCD.
2. Compare the displayed value to a NIST certified thermometer or other
thermometer known to be accurate. For best accuracy, place both the probe
and thermometer in a constant temperature bath.
3. Press the CAL key to enter the temperature calibration mode. The LCD
shows “CA” momentarily and the displayed reading flashes.
4. Press the pandqkeys until the LCD display shows the desired
temperature. The meter allows an adjustable maximum value of±5°C
from the factory default.
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5. To cancel or abort this operation, press the CAL key. Note no new value
will be stored into the meter's non-volatile memory. To confirm the
calibration, press the ENTER key. The LCD displays “CO” momentarily,
and the meter reverts to the measurement mode.
3.4.2 Without Temperature probe (no ATC)
If a temperature probe is not used, the meter compensates for the pH response
based on a new calibrated temperature value manually set or at 25.0 °C
(factory default).
1. Press the MODE key to enter into Temperature mode until “°C” shows on
the LCD.
2. Compare the displayed value to a NIST certified thermometer or
thermometer known to be accurate (dipped into a constant temperature
bath).
3. Press the CAL key to enter the temperature calibration mode. The LCD
shows “CA” momentarily and the displayed reading flashes. Note that this
displayed value should either be 25.0 oC or the last set temperature value.
4. Press pand qkeys until the display shows the desired temperature. Any
value from 0 to 100 oC can be set.
5. To cancel or abort this operation, press the CAL key. Note no new value
will be stored into the meter‘s non-volatile memory. To confirm the
calibration, press the ENTER key. The LCD displays “CO” momentarily,
and the meter reverts to measurement mode.
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4. MEASUREMENT
4.1 Taking Measurements
1. Before measurement, rinse the pH/ORP electrode or Ion Selective
Electrode (ISE) and temperature probe thoroughly with tap or distilled
water to remove any impurities on the bodies of probes.
2. Power on the meter using the ON key. Press the MODE key to select the
desired mode of operation (pH, mV, Ion or Temperature).
3. Dip both probes gently in the test sample, stir gently and wait for the
reading to stabilize. Note the reading. Freeze the displayed reading if
necessary, for details refer to Section 4.3.
4. Rinse the probes with tap water or rinse water thoroughly before taking the
next sample measurement or storing the probes.
4.2 Millivolt (mV) Reference Check
The mV mode is used for the diagnosis of ISE or pH electrode condition. Press
the MODE key to access the mV mode, the “mV” annunciator is displayed.
The displayed value shows the absolute mV value of the ISE or pH electrode
being measured.
4.3 Holding a Reading
To freeze or hold the displayed reading, press the the HOLD key once. The
LCD will display the “HO” annunciator to indicate the HOLD function is
activated.
4.4 Releasing a Held Reading
Press the HOLD key once again to deactivate the HOLD function or to
release the frozen reading. The meter reverts to the current measurement
mode, and the “HO” annunciator disappears from the LCD.
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5. ELECTRODE CARE AND MAINTENANCE
For best results, always keep the ISE capped dry and pH/ORP electrode bulb
wet. Store the pH/ORP glass bulb with pH electrode storage solution. pH
buffers are also suitable. NEVER use deionized water for storage. Wash the
probes thoroughly with distilled water after each use. Because the ISE or pH
electrode is susceptible to contamination or dirt, clean it every 1 to 2 months
depending on extent and condition of use.
Clean the pH/ORP electrode using a mild detergent. Wipe the probe with soft
tissue paper. Avoid touching the glass membrane with your fingers. Wash the
electrode thoroughly in tap water and then in distilled water. Recalibrate the
meter after cleaning the electrode.
6. TROUBLESHOOTING
Problem Cause Solution
No display Batteries not in place a) Insert batteries.
b) Re-insert batteries with correct polarity.
“LO” displays in
the LCD
Low battery Replace batteries with fresh ones.
Unstable
reading
a) Electrode not deep
enough in sample
b) Dirty electrode
c) Broken electrode
a) Place electrode deeper in sample.
b) Clean electrode and recalibrate.
c) Replace electrode.
“Er1” display Buffer value out of
tolerance
Use new pH buffer solution and recalibrate.
“Er2” display Single point Perform at least 2 point calibration.
“Er3” display ISE slope not within
the specified tolerance
Check ISE is in good working condition.
“Er4” display Calibration points not
within 1 decade
Ensure calibration points are at least 1
decade apart.
Not able to
calibrate
a) Display freezes
b) Faulty electrode
a) Release reading by pressing HOLD key.
b) Replace electrode.
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