Ultrameter
™
Operation
Manual
Model 3P
10 - 02 (WEB) EG
MYRON L
COMPANY
MS
MR
pH
MMYYRROONN LL
CCOOMMPPAANNYY
3P
ORP
These 2 Measurement keys will:
• Turn instrument on
• Measure parameter
• Exit any function
Parameters (2)
Wrist/neck strap slot
(user supplied)
pH/ORP Sensor
Protective Cap
This key for:
• Calibration
• Memory Clear
• Confirmation
Up key/Memory Store
Down key/Memory Recall
Displayed here:
• Temperature
readout
• Memory Storage/
Recall
• pH Calibration
Parameter
pH
ORP
Units of Measurement
None
mV - millivolts
* ™DuPont Company
** U.S. Patent #4128468
Teflon* Reference
Junction** under
Glass pH Bulb
ORP
Electrode
pH Glass
Electrode
pH/ORP Sensor
(Replaceable)
BUFFER
mV
°C% /
ORP pH
LOBATT CAL MEMORY
3-23-98
For detailed explanations see Table of Contents
Instrument Illustration
MCLR
CAL
1
ULTRAMETER
TM
FEATURES and SPECIFICATIONS
A. Features
• Accuracy of ±.01 pH/±1 mV @ calibration point.
• All electrodes are internal for maximum protection.
• Waterproof to 3 feet/1 meter.
• Prompts for easy pH calibration.
• Memory saves 20 readings.
• Factory calibrations stored in microprocessor.
B. General Specifications
Display 4 Digit LCD
Dimensions (LxWxH) 7.7x2.7x2.5 in.
196x68x64 mm
Weight 13oz./369g
Case Material VALOX*
pH/ORP Sensor Well Capacity 0.04 oz./1.2 ml
Power 9V Alkaline Battery
Battery Life >100 Hours/5000 Readings
Operating/Storage Temperature 32-132°F/0-55°C
Protection Ratings IP67/NEMA 6 (waterproof to
3 feet/1 meter)
* ™ GE Corp.
D. Warranty/Service
All Myron L Ultrameters have a 2 year warranty except for pH sensors
which have a 6-month limited warranty. If an instrument fails to operate
properly, see the Troublshooting Chart, pg. 18. The battery and pH/ORP
sensor are user replaceable. For other service, return the instrument
prepaid to the Myron L Company.
MYRON L COMPANY
2450 Impala Drive
Carlsbad, CA 92010
USA
760-438-2021
If, in the opinion of the factory, failure was due to materials or
workmanship, repair or replacement will be made without charge. A
reasonable service charge will be made for diagnosis or repairs due to
normal wear, abuse or tampering. This warranty is limited to the repair or
replacement of the Ultrameter only. The Myron L Company assumes no
other responsibility or liability.
E. Ultrameter Models
ULTRAMETER MODELS
PARAMETERS pH/ORP/Temp. Conductivity/TDS Conductivity/TDS/pH
3P 4P 6P
Resistivity/Temp. Resistivity/ORP/Temp
C. Specification Chart
pH ORP3P
Ranges 0-14 pH ±999 mV
Resolution
±.01 pH ±1 mV
Accuracy ±.01 pH ±1 mV
Auto
Temperature
0-71°C
32 - 160°F
Compensation
Additional information available on our web site at:
www.myronl.com
2
3
TABLE OF CONTENTS
VII. CHANGING from CENTIGRADE to FAHRENHEIT . . . . . . . . . . . .14
Instrument Illustration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
FEA TURES and SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 2
A. Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
B. General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . 2
C. Specification Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
D. Warranty/Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
E. Ultramter Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
II. RULES of OPERA TION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
A. Operation in a Nutshell . . . . . . . . . . . . . . . . . . . . . . . . . 6
B. Characteristics of the Keys . . . . . . . . . . . . . . . . . . . . . . 6
C. Operation of the Keys . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Measurement Keys in General . . . . . . . . . . . . 6
2. pH and ORP keys . . . . . . . . . . . . . . . . . . . . . . . 6
3. CAL/MCLR key . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. UP or DOWN keys . . . . . . . . . . . . . . . . . . . . . . .7
III. AFTER USING the ULTRAMETER
Maintenance of the pH/ORP Sensor . . . . . . . . . . . . . . . . .7
IV. THE SPECIFIC RECOMMENDED MEASURING
PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
A. Measuring pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
B. Measuring ORP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
V. CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
A. Calibration Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
B. Rules for Calibration in the Ultrameter . . . . . . . . . . . . . 9
1. Calibration Steps . . . . . . . . . . . . . . . . . . . . . . . .9
2. Calibration Limits . . . . . . . . . . . . . . . . . . . . . . . .9
C. Calibration Procedures . . . . . . . . . . . . . . . . . . . . . . . . 10
1. pH Calibration . . . . . . . . . . . . . . . . . . . . . . . . . 10
2. ORP Calibration . . . . . . . . . . . . . . . . . . . . . . . .12
3. Temperature Calibration . . . . . . . . . . . . . . . . 12
VIII. TOTAL RETURN to FACTORY SETTINGS . . . . . . . . . . . . . . . . . 14
IX. CALIBRA TION INTER VALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
A. Suggested Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . .15
B. Calibration Tracking Records . . . . . . . . . . . . . . . . . . . 15
C. pH and ORP Practices . . . . . . . . . . . . . . . . . . . . . . . . . 15
X. CARE and MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
A. Temperature Extremes . . . . . . . . . . . . . . . . . . . . . . . . 16
B. Battery Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . 16
C. pH/ORP Sensor Replacement . . . . . . . . . . . . . . . . . .16
D. Cleaning Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
XI. TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
XII. ACCESSORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
A. pH Buffer Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
B. pH Sensor Storage Solution . . . . . . . . . . . . . . . . . . . 19
C. Soft Protective Case . . . . . . . . . . . . . . . . . . . . . . . . . . 19
D. Replacement pH/ORP Sensor . . . . . . . . . . . . . . . . . .19
E. Data Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
F. Conductivity/TDS Standard Solutions . . . . . . . . . . . 19
XIII. pH and ORP MEASURING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
A. pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
B. ORP/Oxidation-Reduction Potential/REDOX . . . . . .21
XIV. GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
VI. MEMORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
A. Memory Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
B. Memory Recall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
C. Clearing a Record/Memory Clear . . . . . . . . . . . . . . . . 13
4
5
I. INTRODUCTION
Thank you for selecting the Ultrameter™ Model 3P, one of the Myron L
Company’s latest in a new line of instruments utilizing advanced
microprocessor-based circuitry. This circuitry makes it extremely accurate
and very easy to use (see pages 2 & 3 for Features and Specifications on
this and other models). For your convenience, on the bottom side of your
Ultrameter is a brief set of instructions, and a pocket sized card with
abbreviated instructions is included with the instrument.
II. RULES of OPERATION
A. Operation
Using the instrument is simple:
• Rinse the pH/ORP sensor well with test solution 3 times and refill.
• Press the desired measurement key to start measurement.
Pressing the key again does no harm and restarts the 15 second
“off” timer.
• Note the value displayed or press the MS key to store
(ref. Memory Storage, pg. 12). It’s that simple!
B. Characteristics of the Keys
• Though your Ultrameter has a variety of sophisticated options, it
is designed to provide quick, easy, accurate measurements by
simply pressing one key.
• All functions are performed one key at a time.
• There is no “off” key. After 15 seconds of inactivity the
instrument turns itself off (60 seconds in CAL mode).
• Rarely will a key be required to be held down.
C. Operation of the Keys (See Instrument Illustration on page 1)
1. Measurement Keys in General
Both of the measurement keys in the upper part of the keypad turn on
the instrument in the mode selected. The mode is shown at the bottom
of the display, and the measurement units appear at the right. Pressing a
measurement key does this even if you are in a calibration sequence and
also serves to abandon a change. (ref. Leaving Calibration, pg. 9)
2. pH and ORP keys
Measurements are made on solution held in the pH/ORP sensor well (ref.
pH and ORP Measuring, pg. 19). The protective cap is removed and the
sensor well is filled and rinsed with sample enough times to completely
replace the storage solution.
After use, the pH/ORP sensor well must be refilled with Myron L Storage
Solution and the protective cap reinstalled securely (ref. Maintenance of
the pH/ORP Sensor, pg. 7 and Cleaning pH/ORP Sensors, pg. 16).
6
a. pH key
A press of displays pH readings. No units are displayed.
pH
b. ORP key
A press of displays Oxidation-Reduction Potential/REDOX
ORP
reading in millivolts.
3. CAL/MCLR key
A press of allows you to enter the calibration mode while
CAL
MCLR
measuring pH. Once in CAL mode, a press of this key accepts the new
value. If no more calibration options follow, the instrument returns to
measuring (ref. Leaving Calibration, pg. 9).
While reviewing stored records, the MCLR side of the key is active to
allow clearing records (ref. Clearing a Record/Memory Clear, pg. 13).
4. UP or DOWN keys
While measuring in any parameter, the or keys activate the
MS
MR
Memory Store and Memory Recall functions.
While in CAL mode, the keys step or scroll the displayed value up or
down. A single press steps the display and holding either key scrolls the
value rapidly.
While in Memory Recall, the keys move the display up and down the stack
of records (ref. Memory Recall, pg. 12).
III. AFTER USING the ULTRAMETER
Maintenance of the pH/ORP Sensor
The sensor well must be kept wet with a solution. Before replacing the
rubber cap, rinse and fill the sensor well with (in order of preference):
Myron L Storage Solution, an almost saturated KCl solution, pH 4 buffer
or at least a strong table salt solution. Not distilled water. (ref. Cleaning
pH/ORP Sensors, pg. 16).
IV. THE SPECIFIC RECOMMENDED MEASURING
PROCEDURES
NOTE
After sampling high concentration solutions or temperature
extremes, more rinsing may be required.
A. Measuring pH
1. Remove protective cap by squeezing its sides and pulling up.
7
2. Rinse sensor well 3 times with sample to be measured. Shake
out each sample to remove any residual liquid.
3. Refill sensor well with sample.
V. CALIBRATION
A. Calibration Intervals
Generally, calibration with pH solutions should be checked twice a month.
Calibration of ORP is not necessary. (ref. Calibration Intervals, pg. 15)
4. Press .
pH
5. Take reading.
6. IMPORTANT : After use, fill pH/ORP sensor well with Myron L
Storage Solution, a strong KCl solution or pH 4 buffer, and
replace protective cap. Do not allow pH/ORP sensor to dry out.
NOTE: If none of the above are available, use a saturated solution of
table salt and tap water (ref. Cleaning pH/ORP Sensors, pg. 16).
B. Measuring ORP
1. Remove protective cap by squeezing its sides and pulling up.
2. Rinse sensor well 3 times with sample to be measured. Shake
out each sample to remove any residual liquid.
3. Refill sensor well with sample.
4. Press .
ORP
5. Take reading.
6. IMPORTANT : After use, fill pH/ORP sensor well with Myron L
Storage Solution, a strong KCl solution or pH 4 buffer and
replace protective cap. Do not allow pH/ORP sensor to dry out.
NOTE: If none of the above are available, use a saturated solution of
table salt and tap water (ref. Cleaning pH/ORP Sensors, pg. 16).
B. Rules for Calibration in the Ultrameter
1. Calibration Steps
a. Starting Calibration
Calibration is begun by pressing while measuring pH.
CAL
MCLR
Measuring continues, but the CAL icon is on, indicating calibration is now
changeable.
The reading is changed with the and to match the known
value.
MS
MR
b. Calibration Steps
Depending on what is being calibrated, there may be 1, 2 or 3 steps to
the calibration procedures.
CAL
The becomes an “ACCEPT” key. At each point, pressing
MCLR
CAL
MCLR
accepts the new calibration value and steps you to the next adjustment
(or out of CAL mode if there are no more steps).
To bypass a calibration step, just press to accept the present value
as is.
CAL
MCLR
c. Leaving Calibration
You know you are finished when the “CAL” icon goes out. Pressing
either measurement key abandons changes not yet accepted and exits
calibration mode.
Leaving pH after the 2nd buffer results in the same gain being entered in
place of the 3rd buffer.
In the first four sections, you have learned
all you need to make accurate measurements.
The following sections contain calibration,
advanced operations and technical information.
There are calibration limits. A nominal “FAC” value is an ideal value stored
by the factory. Attempts to calibrate too far from there will cause the
displayed value to be replaced with “FAC”. If you accept it, you will get the
2. Calibration Limits
original default factory calibration for this measurement. The need to
calibrate so far out that “FAC” appears indicates a procedural problem,
wrong standard solution, a very dirty cell cup or a dying pH/ORP sensor
(ref. Troubleshooting Chart, pg. 18).
8
9
C. Calibration Procedures
1. pH Calibration
Important: Always “zero” your Ultrameter with a pH 7 buffer solution
before adjusting the gain with acid or base buffers, i.e., 4 and/or 10, etc.
a. pH Zero Calibration
1. Rinse sensor well 3 times with 7 buffer solution.
2. Refill sensor well with 7 buffer solution.
CAL
3. Press to verify the pH
pH
calibration. If the display
reads 7.0, skip the pH Zero
Calibration and proceed to
section b. pH Gain Calibration.
4. Press to enter calibration mode. The “CAL”, “BUFFER”
CAL
MCLR
Figure 1
BUFFER
pH
and “7” annunciators will appear (see Figure 1). Displayed value
will be the uncalibrated sensor.
NOTES: If a wrong buffer is added (outside of 6-8 pH),“7” and
BUFFER” will flash, and the Ultrameter will not adjust.
The uncalibrated pH value displayed in step 4 will assist in determining
the accuracy of the pH sensor. If the pH reading is above 8 with pH 7
buffer solution, the sensor well needs additional rinsing or the pH sensor
is defective and needs to be replaced.
5. Press or until the display reads 7.0.
MS
MR
6. Press to accept the new value. The pH Zero Calibration is
CAL
MCLR
now complete. You may continue with pH Gain Calibration or exit
by pressing either measurement key.
b. pH Gain Calibration
Important: Always calibrate or verify your Ultrameter with a pH 7 buffer
solution before adjusting the gain with acid or base buffers, i.e. 4 and/or
10, etc. Either acid or base solution can be used for the 2nd point “Gain”
calibration and then the opposite for the 3rd point. The display will verify
that a buffer is in the sensor well by displaying either “Acd” or “bAS”.
1. The pH calibration mode is initiated by either completion of the
pH Zero Calibration, or verifying 7 buffer and pressing the
twice while in pH measurement mode.
CAL
MCLR
2. At this point the “CAL”, “BUFFER” and “Acd” or “bAS”
annunciators will be lit (see Figures 2 and 3).
CAL
BUFFER
pH
CAL
BUFFER
pH
Figure 3Figure 2
NOTE: If the “Acd” and “bAS ” indicators are blinking, the unit is
indicating an error and needs either a acid or base solution present in the
sensor well.
NOTE: Attempted calibration of >1 pH point from factory calibration will
cause “FAC ” to appear. This indicates the need for sensor replacement
(ref. Troubleshooting Chart, pg. 18) or fresh buffer solution. The “FAC”
internal electronic calibration is not intended to replace calibration with pH
buffers. It assumes an ideal pH sensor. Each “FAC” indicates a factory
setting for that calibration step (i.e., 7, acid, base).
You can press to accept the preset factory value, or you can
reduce your variation from factory setting by pressing or .
10
CAL
MCLR
MR
MS
3. Rinse sensor well 3 times with acid or base buffer solution.
4. Refill sensor well again with same buffer solution.
5. Press or until display agrees with buffer value.
6. Press to accept 2nd point of calibration. Now the display
MS
CAL
MCLR
MR
shows the next type of buffer to be used.
11
Single point Gain Calibration is complete. You may continue for
the 3rd point of Calibration (2nd Gain) or exit by pressing either
measurement key. Exiting causes the value accepted for the
buffer to be used for both acid and base measurements.
To continue with 3rd point calibration, use basic buffer if acidic
buffer was used in the 2nd point, or vice-versa. Again, match the
display to the known buffer value as in step 2 and continue with
the following steps.
7. Repeat steps 3 through 6 using opposite buffer solution.
8. Press to accept 3rd point of calibration which ends
Calibration Procedure. Replace protective cap.
2. ORP Calibration
ORP electrodes rarely give false readings without problems in the
reference electrode. For this reason, and because calibration solutions
for ORP are highly reactive and potentially hazardous, your Ultrameter
has an electronic ORP calibration. This causes the zero point on the
reference electrode to be set whenever pH 7 calibration is done.
3. Temperature Calibration
Temperature calibration is not necessary in the Ultrameter.
VI. MEMORY
This feature allows up to 20 readings with their temperatures to be stored
simultaneously for later recall.
A. Memory Storage
1. While displaying a measurement, press to record the
displayed value.
2. “MEMORY” will appear and
the temperature display will be
momentarily replaced by a
number (1-20) showing the
position of the record. Figure
4 shows a reading of 10.00 pH
stored in memory record #5.
B. Memory Recall
1. Press either measurement key.
2. Press , “MEMORY” will appear, and the display will show
the last record stored.
3. Press the or to scroll to the record location desired
(the temperature display alternates between temperature
recorded and location number).
4. Press a measurement key to leave memory recall or allow to
automatically turn off.
C. Clearing a Record/Memory Clear
After recalling a certain record location, press to clear that
memory . This space will be the place for the next memory record,
unless you scroll to another position before ending the recall
sequence. The next memory stored will go into the next highest
available memory location.
Example: You have locations 1-7 filled. You want to clear the ORP
reading stored in record location #3 and replace it with a pH reading.
1. Press and scroll to location #3 .
2. Press to clear old record #3.
3. Fill pH/ORP sensor well with sample.
4. Press to measure sample and press to store
reading in location #3.
5. The next memory stored will go into location #8.
6. To clear all records: After
pressing , scroll down
to “CLr ALL” in measurement
and temperature area
(see Figure 5).
7. Press . All records will be cleared.
12 13
CAL
MCLR
MS
pH
MR
CAL
MCLR
MS
MR
Figure 5
CAL
MCLR
MR
CAL
MCLR
MS
MR
Figure 4
pH
MEMORY
MEMORY
VII. CHANGING from CENTIGRADE to FAHRENHEIT
1. Press .
2. Press to display the stored memory records.
pH
MR
3. Press repeatedly until
MR
you pass the CLr ALL and the
C-F locations. The display will
show a “FAC SEL”
(see Figure 8).
3. Press repeatedly until you pass the memory “CLr ALL”
MR
location”. The display will show a “C” or “F” (see Figures 6 & 7).
Figure 6 Figure 7
4. Press ; the display will change to the other unit.
5. Press ; all temperature readings are now in degrees last
CAL
MCLR
pH
shown.
NOTE: Units symbol “°F” is not displayed in Fahrenheit mode. Tempco
will still be shown in %/°C.
VIII. TOTAL RETURN to FACTORY SETTINGS “FAC SEL”
There may come a time when it would be desirable to quickly reset all the
recorded calibration values in the instrument back to the factory settings.
This might be to ensure all calibrations are set to a known value, or to give
the instrument to someone else free of adjustments or recorded data for
a particular application.
1. Press .
2. Press to display the stored memory records.
pH
MR
4. Press to accept the resetting.
CAL
MCLR
Figure 8
IX. CALIBRATION INTERVALS
There is no simple answer to how often one should calibrate an
instrument. The Ultrameter is designed to not require frequent
recalibration. The most common sources of error were eliminated in the
design, and there are no mechanical adjustments. Still, to ensure
specified accuracy, any instrument has to be checked against chemical
standards occasionally.
A. Suggested Intervals
On the average, the pH function should be checked every 2 weeks to
ensure accuracy. Measuring some solutions will require more frequent
intervals.
B. Calibration Tracking Records
To minimize your calibration effort, keep records. If adjustments you are
making are minimal for your application, you can check less often.
Calibration is purposely limited in the Ultrameter to ±1 pH unit because
more than that indicates the end of the sensor lifetime and it should be
replaced.
C. pH and ORP Practices to Maintain Calibration
1. Keep the sensor wet with Myron L Storage Solution.
2. Rinse away caustic solutions immediately after use.
ORP calibration solutions are not only caustic, but 5% is considered very
accurate. By using the pH zero setting (0 mV = 7 pH) for ORP and
precision electronics for detection, the Ultrameter delivers better
accuracy without calibration than a simpler instrument could using
calibration solutions.
14
15
X. CARE and MAINTENANCE
Ultrameters should be rinsed with clean water after use. Solvents should
be avoided. Shock damage from a fall may cause instrument failure.
A. Temperature Extremes
Solutions in excess of 160°F/71°C should not be placed in the cell cup
area; this may cause damage. The pH sensor may fracture if the
Ultrameter temperature is allowed to go below -10°C (14°F). Care should
be exercised not to exceed rated operating temperature.
Leaving the Ultrameter in a vehicle or storage shed on a hot day can
easily subject the instrument to over 150°F. This will void the warranty.
B. Battery Replacement
Dry Instrument THOROUGHLY . Remove the four (4) bottom
screws. Open instrument carefully; it may be necessary to rock the
bottom slightly side to side to release it from the RS-232 connector.
Carefully detach battery from circuit board. Replace with 9 volt alkaline
battery. Replace bottom, ensuring the sealing gasket is installed in the
groove of the top half of case. Re-install screws, tighten evenly and
securely.
NOTE: Because of nonvolatile EEPROM circuitry, all data stored in
memory and all calibration settings are protected even during power loss
or battery replacement.
C. pH/ORP Sensor Replacement
Order model RPR. When ordering, be sure to include the model and
serial number of your instrument to ensure receiving the proper type.
Complete installation instructions are provided with each replacement
sensor.
D. Cleaning pH/ORP Sensors
The unique pH/ORP sensor in your Ultrameter is a nonrefillable
combination type which features a porous liquid junction. It should not be
allowed to dry out. If it does, the sensor can sometimes be rejuvenated
by first cleaning the sensor well with a liquid spray cleaner such as
Windex™ or Fantastic™ and rinsing well. Do not scrub or wipe the
pH/ORP sensor.
2. Pour DI water in the sensor well and allow to stand for no more
than 4 hours (longer can deplete the reference solution and
damage the glass bulb). Retest.
If neither method is successful, sensor must be replaced.
"Drifting" can be caused by a film on the pH sensor bulb. Spray a liquid
cleaner such as Windex™ or Fantastic™ into the sensor well to clean it.
The sensor bulb is very thin and delicate. Do not scrub or wipe the
pH/ORP sensor.
ORP
Electrode
Sensor
Body
pH Glass
Electrode
Reference
Junction
under Glass
pH Bulb
pH/ORP Sensor
Top View
Leaving high pH (alkaline) solutions in contact with the pH sensor for long
periods of time can damage it. Rinsing such liquids from the pH/ORP
sensor well and refilling well with Myron L Storage Solution, a saturated
KCl solution, pH 4 buffer, or a salty tap water will extend the sensor’s
useful life.
Samples containing chlorine, sulfur, or ammonia can "poison" any pH
electrode. If it is necessary to measure the pH of any such sample,
thoroughly rinse the sensor well with clean water immediately after taking
the measurement. Any sample element which will reduce (add an
electron to) silver, such as cyanide, will attack the reference electrode.
Replacement sensors are available only from the Myron L Company or its
authorized distributors.
Then use one of the following methods:
1. Pour a HOT salt solution ~60°C (140°F), preferably potassium
chloride (KCI) solution — HOT tap water with table salt (NaCl) will
work fine — in the sensor well and allow to cool. Retest.
Or
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displayed repeatedly
1. Temporary condition due to “memory”
of solution in pH sensor well for long
periods.
2. Bulb dirty or dried out.
3. Reference junction clogged or coated.
Will not adjust down to pH 7 pH/ORP sensor has lost KCl.
No response to pH changes Sensor bulb is cracked or an
electromechanical short caused by an
internal crack.
3. Calibration with expired pH buffers.
pH readings drift or respond
slowly to changes in
buffers/samples or “FAC” is
Inaccurate pH readings 1. pH calibration needed. (ref. pH Cal. pg. 10)
measurement key pressed
2. Cross-contamination from residual pH
buffers or samples in sensor well.
Symptom Possible Cause Corrective Action
No display, even though
Battery weak or not connected. Check connections or replace battery.
XI. TROUBLESHOOTING CHART
:
XII. ACCESSORIES
A. pH Buffer Solutions
pH buffers are available in pH values of 4, 7 and 10. Myron L Company
buffer solutions are traceable to NIST certified pH references and are
color-coded for instant identification. They are also mold inhibited and
accurate to within ±0.01 pH units @ 25°C. Order 4, 7 or 10 Buffer.
B. pH Sensor Storage Solution
Myron L Storage Solution prolongs the life of the pH sensor. It is available
in quarts and gallons. Order SSQ or SSG.
C. Soft Protective Case
Padded Cordura® Nylon carrying case features a belt clip for hands-free
mobility. Model: UCC
® Registered trade mark of DuPont
D. Replacement pH/ORP Sensor
Model RPR is gel filled and features a unique porous liquid junction. It is
user-replaceable and comes with easy to follow instructions.
E. Data Port
There is a 4 pin connector marked “Factory Use Only” on the bottom of
the Ultrameter. It is used to interrogate the instrument during final
inspection. Applications in the future for downloading recorded data are
being considered, but not implemented, as of this printing.
Clean and rejuvenate sensor (ref. Cleaning
pH/ORP Sensor, pg. 16) and recalibrate. If
no improvement, replace pH/ORP sensor
(ref. pH/ORP Sensor Replacement, pg.
16).
Clean and rejuvenate sensor (ref.
Cleaning pH/ORP Sensor, pg. 16) and
recalibrate. If no improvement,
replace pH/ORP sensor (ref. pH/ORP
Sensor Replacement, pg. 16).
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Replace pH/ORP sensor (ref.
pH/ORP Sensor Replacement
pg. 16).
2. Thoroughly rinse sensor well.
3. Recalibrate using fresh buffers
(ref. pH Buffer Solutions, pg. 19).
(ref. Battery Replacement, pg. 16)
1. Recalibrate instrument
F. Conductivity/TDS Standard Solutions
For your other Myron L instruments, our NIST standard solutions are
available in a variety of salts and concentrations to fit your needs. Call or
write for information.
XIII. pH and ORP MEASURING
A. pH
1. pH as an Indicator
pH is the measurement of Acidity or Alkalinity of an aqueous solution. It is
also stated as the Hydrogen Ion activity of a solution. pH measures the
effective, not the total, acidity of a solution.
A 4% solution of acetic acid (pH 4, vinegar) - can be quite palatable, but a
4% solution of sulfuric acid (pH 0), is a violent poison. pH provides the
needed quantitative information by expressing the degree of activity
of
an acid or base.
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In a solution of one known component, pH will indicate concentration
indirectly. However, very dilute solutions may be very slow reading, just
because the very few ions take time to accumulate.
2. pH Units
The acidity or alkalinity of a solution is a measurement of the relative
availabilities of hydrogen (H ) and hydroxide (OH ) ions. An increase in
(H ) ions will increase acidity, while an increase in (OH ) ions will increase
-+
-+
alkalinity. The total concentration of ions is fixed as a characteristic of
water, and balance would be 10 mol/liter (H ) and (OH ) ions in a
-7 + -
neutral solution (where pH sensors give 0 voltage).
pH is defined as the negative logarithm of hydrogen ion concentration.
Where (H ) concentration falls below 10 , solutions are less acidic than
+
neutral, and therefore are alkaline. A concentration of 10 mol/liter of (H )
would have 100 times less (H ) ions than (OH ) ions and be called an
+
-7
-
9
+
-
alkaline solution of pH 9.
3. The pH Sensor
The active part of the pH sensor is a thin glass surface which is selectively
receptive to hydrogen ions. Available hydrogen ions in a solution will
accumulate on this surface and a charge will build up across the glass
interface. The voltage can be measured with a very high impedance
voltmeter circuit; the trick is to connect the voltmeter to solution on each
side.
The glass surface encloses a captured solution of potassium chloride
holding an electrode of silver coated with silver chloride. This is as inert a
connection as can be made from metal to an electrolyte. It still can
produce an offset voltage, but using the same materials to connect to the
solution on the other side of the membrane allows the 2 equal offsets to
cancel.
Glass surface
The problem is...the other side of the
membrane is some test solution,
H+ ions
Junction plug
not potassium chloride. The outside
electrode, also called the Reference
Junction, is of the same construction
with a porous plug in place of a glass
barrier to allow the junction fluid to
contact the test solution without
significant migration of liquids
through the plug material. Figure
9 shows a typical 2 component pair.
Migration does occur, and this limits
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Electrode wire
Electrode wire
KCl solution
Figure 9
the lifetime of a pH junction from depletion of solution inside the
reference junction or from contamination. The junction is damaged by
drying out because insoluble crystals may form in a layer, obstructing
contact with test solutions. See Cleaning Sensors, pg. 16.
4. The Myron L Integral pH Sensor
The sensor in the Ultrameter (Figure 10)
is a single construction in an easily
Glass
Surface
H+ ions
Junction plug
Platinum button
replaceable package. The sensor body
holds an oversize solution supply for long
KCl solution
life. The reference junction “wick” is
porous teflon to provide a very stable,
low permeability interface. It is formed
in a ring around the pH sensing electrode.
Glass
Sleeve
The construction combines all the best
features of any pH sensor known.
5. Sources of Error
The basics are presented in Cleaning
Figure 10
Electrode wires
Sensors, pg. 16.
a. Reference Junction
The most common sensor problem will be a clogged junction because a
cell was allowed to dry out. The symptom is a drift in the “zero” setting at 7
pH. This is why the Ultrameter does not allow more than 1 pH unit of offset
during calibration. At that point the junction is unreliable.
b. Sensitivity Problems
Sensitivity is the receptiveness of the glass surface, which can be
diminished by a film on the surface, or a crack in the glass. These
problems also cause long response time.
c. Temperature Compensation
pH sensor glass changes its sensitivity slightly with temperature, so the
further from pH 7 one is, the more effect will be seen. A pH of 11 at 40°C
would be off by 0.2 units. The Ultrameter senses the cell temperature and
compensates the reading.
B. ORP/Oxidation-Reduction Potential/REDOX
1. ORP as an Indicator
ORP is the measurement of the ratio of oxidizing activity to reducing
activity in a solution. It is the potential of a solution to give up electrons
(oxidize other things) or gain electrons (reduce).
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Like acidity and alkalinity, the increase of one is at the expense of the
other, so a single voltage is called the Oxidation-Reduction Potential,
with a positive voltage showing a solution wants to steal electrons
(oxidizing agent). Chlorinated water will show a positive ORP value, for
instance.
2. ORP Units
ORP is measured in millivolts, with no correction for solution temperature.
Like pH, it is not a measurement of concentration directly, but of activity
level. In a solution of only one active component, ORP does indicate
concentration. Also, as with pH, a very dilute solution will take time to
accumulate a readable charge.
XIV. GLOSSARY
Logarithm - An arithmetic function. pH Units, pg. 20.
ORP - Oxidation-Reduction Potential or REDOX, See ORP/
Oxidation-Reduction Potential/REDOX, pg. 21.
3. The ORP Sensor
An ORP sensor uses a small platinum surface to accumulate charge
without reacting chemically. That charge is measured relative to the
solution, so the solution “ground” voltage comes from a reference
junction - same as the pH sensor uses.
4. The Myron L ORP Sensor
Figure 10 pg. 21 shows the platinum button in a glass sleeve. The same
reference is used for both the pH and the ORP sensors. Both pH and
ORP read out 0 for a neutral solution. Calibration at zero compensates for
error in the reference junction.
A zero calibration solution for ORP is not practical, so the Ultrameter uses
the offset value determined during calibration to 7 in pH calibration (pH 7
= 0 mV). Sensitivity of the ORP surface is fixed, so there is no gain
adjustment either.
5. Sources of Error
The basics are presented in Cleaning pH/ORP Sensors, pg. 16 because
sources of error are much the same as for pH. The junction side is the
same, and though the platinum surface will not break like the glass pH
surface, its protective glass sleeve can be broken. A surface film will slow
the response time and diminish sensitivity. It can be cleaned off with
detergent or acid, as with the pH glass.
For details on specific areas of interest refer to Table of Contents.
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