Portable PH meter MSLZJ019 Acceptance
Please check the following device in the instrument box:
- portable pH meter 1 computer
- The composite electrode 1
- short-circuit plug (has been inserted in the instrument back electrode socket) 1
- 7 DC1.5V batteries (by express delivery is allowed) 4
- standard buffer reagent: 1 set of pH4, pH6.86, pH9.18
- use manual 1
- product warranty card 1
- product certificate in 1 copies
- environment temperature: 0 ~ 40 ℃ relative humidity: < 85%
- for electric power: 1.5V battery /4 Festival
- No significant vibration
- except without external magnetic field of the earth magnetic field interference
- The input impedance: ≥ 1 × 1012 Ω
- drift: ≤ 0.01pH ± 1 words / 2 hours
- solution temperature compensation range: 0 ~ 60 ℃
- The size and weight: 180 * 80 * 30MM (length * width * height) 0.5Kg
- power consumption: 2 W
3，The instrument work principle
The basic principle of pH measurement
Measurement of pH value in the water solution with glass electrode as indicator electrode, calomel electrode as reference electrode, when the hydrogen ion concentration in solution (strictly speaking is activity) that the pH value of the solution changes, electromotive force generated between the glass electrode and a calomel electrode with the change, and the potential relationship with the following formula:
- E pH = 58.16 * * (273+t ℃) /293 (mV)
- E: indicates the potential change, the MV unit. (mV)
- pH: the pH values of the solution.
T: that of tested solution temperature (C).
Indicator electrode used a glass electrode, the electrode, fluoride electrode, silver electrode, the glass electrode is the most widely used. PH glass electrode head is made of sensitive film special, it is sensitive to hydrogen ions, when it is inserted into the test solution, the potential change with hydrogen ion concentration and temperature of the solution. In the solution temperature is 25 ℃, 1 per pH, the electrode potential changes 59.16mV. The theory of slope coefficient which is often said that the electrode.
The commonly used reference electrode for calomel electrode, the potential does not vary with the concentration of hydrogen ions in the solution was changed.
The measurement of pH value is the essence of the measured potential difference between two electrodes. When the potential of a pair of electrodes in the solution of the resulting difference is equal to zero, the measured pH value of the solution is zero potential value pH, it with the glass electrode in the solution of the relevant.
The instrument used is composite electrode is composed of a glass electrode and Ag-Agcl electrode consisting of zero position, the pH value of 7 ± 0.25pH.
4，Method of use instrument
open the instrument back battery cover, install 1.5V 4 batteries (note the positive and negative class). 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.
Switch on 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: 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 as 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.
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 pH7 and pH4 calibration; if the measurement range of only alkaline range (≥ 7pH), select the pH7 and pH10 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, it must carry out the three point calibration of the instrument, the slope adjustment to consistent with pH electrode.
Note: PHB-4 pH meter with E201-C-W plastic PH three composite electrode or the 018 electrode of instrument temperature, automatic temperature compensation PH test.
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，Use and maintenance of instrument and matters needing attention
The instrument is good or bad, in addition to the instrument itself structure, and the proper maintenance, standardized operation and correct methods are inseparable.
Note the sample The electrode plug and socket instruments must be kept clean and dry, when not in use should be short plug or the electrode plug, in order to prevent dust and moisture and reduce the input impedance instrument, accuracy of measurement.
different samples, pH electrode selecting suitable (for example: measurement of acid, alkali or water etc.). In the sample survey, the introduction of the electrode wire to keep still, touch not.
Otherwise it will lead to unstable measurements.
The preparation of standard solution must be used two times with distilled water or
deionized water, its conductivity less than 2 μ S/cm, the best boiled use.
to ensure accurate and reliable standard buffer solution, alkaline solution should be installed in the polyethylene bottle sealing gaijin. Standard buffer should be stored in the refrigerator (low temperature 5 ~ 10 ℃) in preservation, generally can be stored for 2 to 3 months. Such as found in turbid, moldy, or precipitation phenomenon, can not continue to use.
do not use more than the standard buffer shelf life, do not use the standard buffer rewind standard liquid storage bottle. calibration, as much as possible close to the standard buffer pH values of the samples, and the calibration liquid temperature as much as possible with the sample temperature is the same.
The instruments used in the process if the replacement of the electrode, the best off after the boot,re calibration.
Note the use of electrode
The composite electrode should not be long-term immersion in distilled water, when not in use, should be equipped with electrode electrode insertion protection liquid bottle, the bubble
remain active electrode ball.
Preparation of the electrode protection liquid: take the pH4.00 buffer (250ml) a bag, dissolved
in 250 ml ion in water, then add 56g of pure Kcl, stirring until completely dissolved into.
take down electrode protective sleeve, should avoid electrode head collision, so as to avoid e
lectrode glass ball bubble burst, the electrode failure.
use liquid type electrode, attention should be paid to electrode internal reference fluid is
reduced, if less than 1/2 volume, available from the upper holes added. Measurement should
be sealing sleeve downwards, so as to expose holes.
before the electrode from one solution to another solution, using distilled water cleaning
electrode, using filter paper will sop up water. Don't wipe electrode glass bulb, or may lead
to delayed electrode response. The best approach is to use the tested liquid rinse electrodes.
should avoid electrode internal bubble partition than the liquid, if bubbles can swing
electrode, to eliminate.
The temperature of solution resistance, response time and electrode the instrument
indication of the nature of the solution and the solution is very low, especially in the
measurement of the dissociation degree (such as water), as well as the solution temperature
is low or electrode aging, instrument, showing the value of stable time will be longer.
test acid, alkali or special solution (such as: contains protein, paint and other solution),
should minimize the soaking time, carefully cleaned after use. The best method is to choose a
E314 composite electrode.
electrode after long-term use, the electrode slope and response speed will reduce. The electrode
bulb HCl solution with dilute 0.1mol/L (preparation: 9mlHCl ionic water dilution to 100ml) for
24 hours, if the passivation is more serious, the electrode bulb dipped in 4%HF solution (mlHF:
4 preparation of ion water dilution to 100ml) in 3 ~ 5 seconds, with distilled water after cleaning,
in the electrode protection solution, make appropriate recovery. If the two methods can not recover,
please replace the electrode.
In the sample solution containing the easy pollution sensitive bulb or blockage of the reference
electrode liquid junction substances (such as suspension, emulsion, viscous liquid) will make
the electrode passivation. The phenomenon is the decrease of sensitivity, or reading the
drift instability, misalignment. So, it should be according to the nature of pollution, with
appropriate cleaning solution, and then the distilled water to solvent, into the electrode
protection solution, so as to restore.
Cleaning method the pollution matter: (Gong Cankao)
Pollutant cleaning agent
Inorganic metal oxide concentration less than 1mol/L of dilute acid
Organic grease alkaline dilute detergent
Resin polymer alcohol, acetone, ethyl ether
The protein precipitate acidic blood enzyme solution (such as sacccharated yeast tablets)
Pigment substances diluted bleach, hydrogen peroxide
note: selection of cleaning agents, if the use of washing liquid dissolved poly carbonate resin,
such as carbon tetrachloride, three vinyl chloride, tetrahydrofuran, may the poly carbonate resin
(electrode) dissolved on sensitive glass bulb, and the electrode failure, please caution!
Check and judgement of trouble
Most measurement problems are derived from the electrode failure or measurement error, rather
than the instrument itself. In addition, many factors of standard buffer used, samples will also
lead to a problem, please careful analysis, to identify the problem.
If the instrument host normal, and electrode matching test, showing the value of instability
or the instrument response is very slow; reproducibility is poor; or cannot be calibrated to the
desired pH value, please check the electrode:
Patch is good, the electrode lead is loose or broken ends;
Electrode is immersed in the sample bulb;
Whether there is bubble electrode in solution;
Electrode bulb is contaminated;
If the above, please replace with new electrode.
the standard buffer solution
If the host, the electrode were normal, incorrect readings or not calibration, check the buffer solution:
Whether to use the correct pH standard buffer solution;
Check the buffer exceeds the shelf-life or contaminated;
If you re prepared pH standard buffer solution.
6，Preparation of standard buffer solution
The standard buffer reagent instrument with respectively into 250ml volumetric flask,
with two times distilled water (preferably boil) washing reagent plastic bags after dissolved
and diluted to the scale, shake the standby.
Commonly used standard buffer solution pH value and temperature relationship table: