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Electric Conductivity meters

Electrical conductivity (EC) estimates the amount of total dissolved salts (TDS), or the total amount of dissolved ions in the water.

TDS: Total dissolved salts or solids in a volume of water; usually in mg/l; estimated by EC (electrical conductivity) TDS tell how many units of impurities there are for one million units of water. TDS stands for the total dissolved substances (i.e. salts and minerals) in water remaining after evaporating the water and weighing the residue.

To convert the electric conductivity of a water sample (mS/cm) into the approximate concentration of total dissolved solids (ppm), the mS/cm is multiplied by a conversion factor. The conversion factor depends on the chemical composition of the TDS and can very between 0.54 ? 0.96. A value of 0.67 is commonly used as an approximation if the actual factor is not known [(TDS)ppm = Conductivity µS/cm x 0.67].

What in the world are microSiemens per centimeter (µS/cm)?

These are the units for electrical conductivity (EC). The sensor simply consists of two metal electrodes that are exactly 1.0 cm apart and protrude into the water. A constant voltage (V) is applied across the electrodes. An electrical current (I) flows through the water due to this voltage and is proportional to the concentration of dissolved ions in the water - the more ions, the more conductive the water resulting in a higher electrical current which is measured electronically. Distilled or deionized water has very few dissolved ions and so there is almost no current flow across the gap (low EC). 

Up until about the late 1970's the units of EC were micromhos per centimeter (µmhos/cm) after which they were changed to microSiemens/cm (1 µS/cm = 1 µmho/cm). You will find both sets of units in the published scientific literature although their numerical values are identical. 

Since the electrical current flow (I) increases with increasing temperature, the EC values are automatically corrected to a standard value of 25°C and the values are then technically referred to as specific electrical conductivity.

CONDUCTIVITY AND TOTAL DISSOLVED SALT VALUES 

                                           EC (µS/cm)              TDS (mg/L)

Distilled water                        0.5 - 3
Pure rainwater                       < 15
Mixed fisherie water           150 - 500
Ideal drinking water                                            0 - 50
Average tap water                                          140 - 400
Tap water Trier/Germany         251                       181
Drinking water general                                      <   500
EPA's max. contamin. level                                      500 
Unfit for human consumption                            > 1,000       
Agriculture water                                               < 1200
Fresh water                        0 -  1 990
Brakish water                     0 - 19 900
Atlantic Ocean                      43,000                   35,000
Sea water                        up to 50 000
Great Salt Lake                  158,000                 230,000
Dead Sea                                 ?                    ~330,000

Classification of saline waters

Water Class Electrical conductivity dS/m Salt concentration mg/l Type of water
Brine >45 >45 000 Seawater
Non-saline <0.7 <500 Drinking and irrigation water
Slightly saline 0.7 - 2 500-1500 Irrigation water
Moderately saline 2 - 10 1500-7000 Primary drainage water and groundwater
Highly saline 10-25 7000-15 000 Secondary drainage water and groundwater
Very highly saline 25 - 45 15 000-35 000 Very saline groundwater

PH Meters

It is simply the symbol of a scale, numbered from 0 to 14, that rates water solutions according to their acidity or alkalinity. Pure water is given the number 7 - right in the middle of the scale - because it contains an equal number of acidic and basic ions and is therefore neutral. As the alkalinity of a solution increases, the pH value goes up; as the acidity increases, the pH goes down. Each step represents an increase or decrease by a factor of ten.

The pH of a sample of water is a measure of the concentration of hydrogen ions. The term pH was derived from the manner in which the hydrogen ion concentration is calculated - it is the negative logarithm of the hydrogen ion (H+) concentration. What this means to those of us who are not mathematicians is that at higher pH, there are fewer free hydrogen ions, and that a change of one pH unit reflects a tenfold change in the concentrations of the hydrogen ion. For example, there are 10 times as many hydrogen ions available at a pH of 7 than at a pH of 8. The pH scale ranges from 0 to 14. A pH of 7 is considered to be neutral. Substances with pH of less that 7 are acidic; substances with pH greater than 7 are basic.

The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH may also determine whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.

Electric conductivity meter: KL-138

Technical Specification: 

Measuring range: 10. -1990. us/cm 
Accuracy: ±0.2% F.S
Resolution: 10 us/cm 
Display: 3-digital LCD 
Temperature: 0~50
Temperature compensation:0-50℃ 
Power supply: DC 4×1.5V(AG13)
Dimension: 142mm(L)×29mm(W)×15mm(H) 
Weight: 51g

Characteristics: 

No need to adjust normally 
Easy operation 
Reliable and stable 
Easy to carry

TDS Tester: KL-139A

Measuring range 0~1999 PPm(mg/L)
Accuracy ±2℅F·S
Resolution 1 PPm(mg/L)
Display 4-digital LCD
Environment Humidity:≤95℅
Automatic Temperature Compensation 0°~50°
Power Supply 4×1.5V (AG13)
Dimensions 165×26×26 (mm³)
Weight 63g

PH Tester: KL-009 (III)

The KL-009 (III) is a high accuracy pen type PH meter using combined pH electrode of high sensitivity , fast response and good repetition as probe. With 31/2 liquid crystal digits display, the meter is reliable, stable, portable and convenient to operate. It is ideal for field measuring.

Measuring range 0.00~14.00PH 0°~55°
Accuracy ±0.1PH ±1°
Resolution 0.01PH 0.1°
Operating Temperature 0°~50°
Automatic Temperature Compensation 0°~50°
Power Supply 4×1.5V (AG13)
Dimensions 170×36×23 (mm³)
Weight 91g

Characteristics: 
- Easy-to-read Custom Dual-level LCD 
- On-the-spot measurement 
- Automatic Temperature Compensation 
- Stability Indicator

Combined Tester: Electric Conductivity/TDS/CF Meter: KL 1385 EC/CF/TDS

- Large and easy-to-read LCD 
- Waterproof design to withstand wet environment 
- Measures 3 parameters including EC,CF,TDS using one electrode 
- Hold Function?Saves measurements for convenient reading and recording 

Measuring range EC 0.00~19.99 EC
                            CF 0.0~199 CF
                            TDS 10~19990 ppm

Resolution            EC 0.01 EC 
                            CF 0.1 CF
                            TDS 10 ppm

Accuracy ±2℅F·S
Operating Temperature 0°~50°
Automatic Temperature Compensation 0°~50°
Power Supply 4×1.5V (AG13)
Dimensions 185×38×38 (mm³)