Cheap Microcomputer desktop PH meter MSLZJ020
The instrument is composed of an intelligent control of pH microprocessor design,
selection of high reliable imported integrated element and the strict screening and refined,
stable and reliable performance, simple operation. Suitable for laboratory precision
measurement of solution acidity (pH value) and the electrode potential (mV), widely
used in light industry, chemical, electrochemical analysis of pharmaceutical, food,
epidemic prevention, environmental protection and education scientific research departments.
The "manual" will complete guide you install and use. At the same time, also on the
equipment maintenance, maintenance and matters needing attention are introduced
in this paper. Please read the "manual", so that you can use our products better, improve the
efficiency of your work.
Before using this instrument, please take a few minutes to fill in the "manual" attached to the
user registration card and mail or e-mail to our company. Company customer service engineer
to more effectively to provide you with technical support and after sale service.
In the instrument within the warranty period, if quality problems, please contact the dealer or the
Sales Department of the company. We will conscientiously quickly for you to solve.
If you use the instrument problems, see the "manual" if can't solve, welcome to our customer service
1、 out of the box and acceptance
After unpacking the instrument, please check the following devices:
- MSLZJ020 pH meter(1)
- PH composite electrode(1)
- short circuit plug (plug electrode jack on the rear of the instrument)(1)
- electrode holder(1)
- Power adapter (9V DC output)(1)
- standard buffer reagents: pH4, pH 6.86, pH 9.18(1)
- User Guide(1)
- Ambient temperature：0 ~ 40 ℃； Relative Humidity： <85%
- Electricity Supply source：9V DC power supply
- no significant vibration
- In addition to the Earth's magnetic field external magnetic field interference
- Input impedance：≥ 1 × 1012Ω
- zero drift： ≤ 0.01pH ± 1 word / 2 hours
- solution temperature compensation range：0~ 100 ℃
- Dimensions and weight：230 × 200 × 60mm (length × width × height) 1.2Kg
3、 the instrument works
pH Measurement Fundamentals
The measurement of pH of aqueous solutions are generally using a glass electrode as the
indicator electrode, calomel electrode as the reference electrode, when the hydrogen ion
concentration in the solution (strictly speaking, activity) that the pH value of the solution is changed, a glass electrode and a calomel electrode generated between the electric potential also changes with the potential change relationship meets the following f ormula:
- E = -58.16 × △ pH × (273 t ℃) / 293 (mV)
- E: represents the electric potential changes in millivolts. (MV)
- pH: the changes of the pH of the solution.
- t: indicates the measured solution temperature (° C)。
Top indicator electrode is a glass electrode, an antimony electrode, a fluorine electrode, the silver electrode, etc., in which the glass electrode is most widely used. The head of the pH glass electrode is made by a special sensitive thin film, in its hydrogen ion sensitive, insert it into a test solution, the potential change with the concentration of hydrogen ions in the liquid under test and temperature.
Solution temperature of 25 ° C, each change of one pH electrode potential change 59.16mV.
This is often said that the theoretical slope coefficient of the electrode.
Commonly used reference electrode was a calomel electrode, its potential does not change with the hydrogen ion concentration in the test solution. the pH measurement essence measuring the potential difference between the two electrodes. When the potential difference is generated by a pair of electrodes in the solution is equal to zero, the value of the measured pH of the solution that the pH value of zero potential value, it is concerned with the solution in the glass electrode. The instrument is equipped with is integral with the composite electrode by a glass electrode and an Ag-AgCl electrode, its zero-bit pH at 7 ± 0.25pH.
Circuit works manager
Due to the high internal resistance of the glass electrode, about 2 × 108Ω, therefore, the instrument is actually a high-input impedance of the DC amplifier, the impedance
transformation is obtained through the high input impedance of the IC. Due to the related to the pH of the solution and temperature; glass electrode MV-pH conversion slope generally less than the theoretical value, and with the use and storage of the time of growth decreased; between electrodes of presence of certain discrete; therefore need an instrument having a temperature compensation and electrode slope compensation. Temperature compensation of the instrument and the electrode of the pH-mV the conversion slope compensation and pH positioning, correction by the microprocessor automatically control and adjust.
4、the instrument to use
Preparation the power adapter into 220V AC power supply, DC output plug is inserted into the instrument panel on the "DC9V" power jack. The electrode is arranged on the electrode frame, take short plug of instrument electrode socket, plug electrode. Note that the electrode plug should be kept clean and dry before use, should not be pollution. power press to open the key, preheat for 5 minutes.
Note: this instrument must use 4, 6.86, 9.18, three kinds of standard buffer solution calibration
In the pH before the measurement, we need to instrument calibration. To obtain accurate measurement results, calibration with standard buffer solution should be accurate and reliable.
Plug in the power, press the "switch" boot. Unscrew the short-circuit protection pH socket on the cover, access plastic pH composite electrode,the electrode in pure water and clean and dry.
By measuring the pH thermometer buffer solution temperature, pressing the button "∧" or reduce the key "∨" will display the temperature value accurate adjustment.
The location and calibration, the pH electrodes immersed in pH6.86 buffer, stir it still be placed, measured value stability, hold down the "calibration" key and do not put, let go when the LCD screen display CAL symbol, to show flashes of 6.86, after a few seconds display End symbols, and then show the pH calibration (this pH is displayed value varies with temperature, such a s 25 ℃ showed 6.86, 15 ℃ showed 7.04 of these are numerical, built-in chip set below).
Said to complete the calibration and memory.
The slope of calibration of I: remove the PH electrode, pure water and clean and dry, then PH electrodes immersed in pH4.00 buffer, stir it still be placed, measured value stability, hold down the "calibration" key and do not put, let go when the LCD screen displays the CAL symbol, the first display flashing 4, a few seconds after the show End symbol, and then display the pH calibration values, indicating the completion of calibration and memory. After the calibration will automatically display electrode in the linear section of the slope percentage.
The slope of calibration of II: remove the pH electrode, pure water and clean and dry, then
PH electrodes immersed in pH9.18 buffer, stir it still be placed, measured value stability, hold
down the "calibration" key and do not put, let go when the LCD screen displays the CAL symbol,
the first display flashing 9.18, a few seconds after the show End symbol, and then display the pH calibration values, indicating the completion of calibration and memory. After the calibration will automatically display electrode in the linear section of the slope percentage.
By measuring the solution temperature (temperature water temperature automatic detection electrode), and then press a button to increase or decrease key V will instrument temperature adjustment is accurate, the pH electrode cleaning after immersion in a solution to be measured, stir it still be placed, measured value stability when reading, namely for the measured value of pH.
According to the pH isotherm measurement principle, the measured temperature and calibration
solution temperature is close, the measurement accuracy is higher, the actual test should be observed.
This instrument built-in smart chip, can be a point, two point or three point calibration automatically, if the measurement accuracy ≤ 0.1pH, as long as the use of pH buffer solution was one point calibration can be; if the measurement range only in the acidic range (≤ 7pH), select the pH6.86 and pH4.00 calibration; if the measurement range of only alkaline range (≥ 7pH), select the pH6.86 and pH9.18 calibration; if the measurement range is wide, or pH electrode is used for a long time aging phenomenon, should choose three point calibration, it will make the higher measurement accuracy, pH electrode is used for the first time, must be three point calibration of the instrument, the slope of the adjusted and the pH electrode.
Test mV value:
Press "pH/mV" key, the instrument switch to the "mV" file,
The ion selective electrode (ORP electrode or other) is inserted into the test solution,
stir it still be placed, measured value stability after reading, potential is measured ORP
values or the values of the ion electrode
5、Instrument maintenance and use precautions
The good and bad of the instrument, in addition to the instrument itself structure, with proper
maintenance, standardized operation and correct methods are inseparable. Measurement sample Note instrument the electrodes plug and jack must be kept clean and dry when not in use, the short circuit plug or electrode plug in to prevent dust and moisture immersion and reduce the input impedance of the instrument, affect the measurement accuracy.
Different samples should be selected to adapt the pH of the electrode (for example:
the measurement of acid, alkali, or pure water, etc.).
Sample measurement, the electrode of the introduction of wire should be kept still,
do not touch. Failure to do so will cause measurement instability.
Preparation of standard solution must be used twice-distilled water or deionized water,
the conductivity should be less than 2 μS, preferably boiling use.
standard buffer to ensure accurate and reliable, the alkaline solution should be packed
in a polyethylene bottle sealed tightly. The standard buffer should be stored in the
refrigerator (low temperature 5 ~ 10 ℃) Save generally can be stored for three months.
Such as muddy, moldy, or precipitation and other phenomena, can not continue to use.
Do not use more than the shelf life of the standard buffer Do not use the standard rewind
buffer the standard liquid storage bottle.
calibration, as much as possible close to the sample pH standard buffer, and calibration
of the temperature of the liquid as possible consistent with the temperature of the sample.
In the process of using the instrument to replace the electrode, the best power-cycle, re-calibration.
Notes of the electrodes used
composite electrodes should not be long-term immersion in distilled water, when not in use,
should the electrode insertion protection solution bottle equipped with electrodes, so
that the electrode bulb to maintain the active state.
the electrode protection solution preparation: take pH4.00 buffer (250ml) bag, dissolved in
250 ml of deionized water, then add 56g of analytical grade Kcl, stirring until completely
Remove the electrode protective sleeve should avoid electrode head collision, in order to
avoid the glass bulb of the electrode breakage, failure of the electrode.
plus liquid electrode, should pay attention to whether the reduction of the the electrode
internal reference solution, if less than 1/2 the volume of available dropper joined from the upper end of the hole. Measurement should be the sealing sleeve to move down to expose the hole.
Before the electrode is shifted from one solution to another solution, the application of distilled
water to clean the electrode, sucking up the water with a filter paper. Do not bother to wipe the
glass electrode bulb, otherwise it could lead to the slow response of the electrode. The best method is to use the measured liquid rinse electrode.
should avoid the the electrode internal reference bubble cut off, if bubbles in the liquid lashing
electrode, so eliminate.
value of the response time of the instrument is shown with the internal resistance of the electrode and the temperature of the solution as well as the nature of the solution, especially in the measurement of a low degree of dissociation solution (e.g., pure water), as well as lower temperature of the solution or the electrode aging, apparatus, showing the value settling time will be longer.
test acids, alkalis or the particularity solution (such as: a solution containing protein, paint), should try to reduce the soaking time, carefully cleaned after use. The best way is to select a E314 composite electrode.
electrode after long use, the slope of the electrode, and the response speed will be reduced.
Electrode bulb with 0.1mol / L dilute HCl solution (preparation: 9mlHCl diluted with deionized
water to 100ml) soak for 24 hours, if the passivation is more serious, the electrode ball immersion in 4% HF solution (preparation: 4 mlHF was diluted with deionized water to 100ml) for 3 to 5 seconds, and after washing with distilled water, placed in the electrode protecting soaking liquid, so that proper recovery. Neither approach can recover, replace the electrode.
in the sample solution containing an easily contaminate sensitive ball bubble or clogging
the reference electrode liquid junction of substances (such as suspensions, emulsion, viscous
liquid, etc.) causes the electrode passivation. The phenomenon is a reduction in the sensitivity
or the readings drift instability inaccurate. So, according to the nature of the pollutants should be
an appropriate solution to clean, use distilled water to wash away the solvent, soaking into the
electrode protection, so as to restore.
pollutants cleaning methods: (for reference)
- Pollutants--cleaning agent
- Inorganic metal oxide--concentrations below 1 mol / L dilute acid
- Organic fats and oils-- weak dilute alkaline detergent
- Resin, polymeric substance--alcohol, acetone, diethyl ether, etc.
- Protein blood cell precipitate--acidic enzyme solution (such as food born tablets)
- Pigment classes substance-- dilute bleach, hydrogen peroxide, etc.
Note: selection of cleaning agent, if used cleaning solution dissolving the polycarbonate
resin, such as carbon tetrachloride, trichloro-hexene, tetrahydrofuran, etc., can polycarbonate
resin (electrode material) may be dissolved in the sensitive glass balls coated taking a dip,
leaving the electrode failure, caution!
Check with the judgment of the general failure
Electrode failure or measurement method most measurement problems arise due to an error,
rather than the instrument itself. In addition, the use of the standard buffer, sample many factors
can lead to the emergence of the problem, a careful analysis to determine where the problem is.
If it is determined that the normal host of instruments, with the electrode supporting the test,
showing the value of instability or instrument response is very slow; poor reproducibility;, or can
not be calibrated to the desired pH value, check the electrode：
（1）Patch is good at both ends of the electrode lead is loose or disconnected;
（2）Electrode bulb is immersed in the sample;
（3）Electrodes within the existence of bubbles in the solution;
（4）Electrode bulb is contaminated;
If the above situation, replace the new electrode.
If the host, the electrodes were calibrated reading is incorrect or can not check the buffer solution:
（1）Are using the correct pH standard buffer;
（2）Check whether the buffer exceeds the shelf life or pollution inaccurate;
If you re-formulated pH standard buffer.
6、 the standard buffer preparation
Instrument with standard buffer reagents were poured into 250ml volumetric flask) flush reagents plastic bags dissolve and dilute to the mark with double-distilled water (preferably boil, shake spare.