Prm unit of measurement is converted to percentage. Gas analyzers and units of measurement

Product defects are expressed equally often both in percentage, and in relation to a million samples produced. You can argue about the pros and cons of this or that method of expression for a long time. In my practice, I most often use the expression of defectiveness in relation to a million samples and find it more convenient. However, the calculation methods discussed in this article can be easily transferred to percentages.

Product defectiveness is a characteristic that describes the number of defective samples in a batch or a certain number of produced samples. In this case, we will use the PPM (Parts Per Million) indicator - the number of defective samples in relation to a million manufactured.

PPM = number of samples defective / million samples produced

2500 ppm means that out of a million products manufactured, 2500 may be defective.

The point is to determine how many defective samples we will get when producing 1 million products. Please note that we are not talking about defects, but about defective samples. Those. When calculating, it is not the number of defects that is taken into account, but the number of products containing at least one defect. Each defective sample can contain an unlimited number of defects, and yet, it is the number of samples that is taken into account.

To calculate the indicator, you do not need to wait until a million products are produced. When calculating, any number of observed products can be taken into account. In this case, the calculation formula will take the following form:

PPM = (number of defective samples / number of samples produced) 1,000,000

For example, 750 products were produced, 36 of which did not pass quality control and turned out to be defective. Thus:

PPM = (36 / 750) 1,000,000 = 48,000

Using PPM to Assess Quality in Sampling Inspections

When using a metric to account for the results of sampling, the question arises of how to relate the number of defective samples found - to the sample size or the lot size?

The number of defective samples found in the sample is compared with the estimated number, on the basis of which a conclusion is made about the suitability or unsuitability, acceptance or non-acceptance of the entire batch. If the batch is accepted based on the inspection results, the number of defects is compared with the number of products in the batch. If a batch is blocked, the number of defects is compared with the sample size. After sorting the batch, the total number of defective samples found is compared to the number of products tested. The calculation formulas are given below:

• For accepted batch:
  PPM = (number of defective samples / lot size) 1,000,000
• For rejected batch:
  PPM = (number of defective samples / sample size) 1,000,000
• For a batch of products after sorting:
  PPM = (number of defective samples / number of tested samples) 1,000,000

The last formula is also used for multi-level sampling control. For example, a batch of 1000 samples was randomly tested. Sample size: 50 samples. 2 defective samples were found, which is within the tolerance for this case. The calculation is carried out as follows:

PPM = (2 / 1,000) 1,000,000 = 2,000 ppm

If the batch was rejected (2 defective samples out of 50 is not acceptable), the calculation is carried out as follows:

PPM = (2 / 50) 1,000,000 = 40,000 ppm

The rejected batch was 100% inspected, resulting in another 37 defective items being found. So the final result looks like this:

PPM = [(2 + 37) / 1,000] 1,000,000 = 39,000 ppm

Instead of the PPM indicator, DPM (Defects Per Million) is sometimes used - the number of defects per million products. Although both indicators can reflect the same value - the number of defective samples in a million products - they should be distinguished and used for different purposes. DPM, as a measure of the number of defects per million samples, is certainly less commonly used than PPM, but can reveal much more about a process.

Gas analyzer- This measuring device to determine the qualitative and quantitative composition of gas mixtures. There are manual and automatic gas analyzers. Among the former, the most common are absorption gas analyzers, in which the components gas mixture are sequentially absorbed by various reagents. Automatic gas analyzers continuously measure any physical or physico-chemical characteristic of a gas mixture or its individual components.

ppm(ppm) - a unit of measurement of concentration, and other relative quantities, similar in meaning to percent or ppm. It is designated by the abbreviation “ppm” (from the English “parts per million”, read pi-pi-em, “parts per million”).

1 ppm = 0.001 ‰ = 0.0001% = 0.000001 = 10 -6

For example, if it is stated that the mass fraction of a substance in a mixture is 15 ppm, this means that for every kilogram of the mixture there are 15 mg of this substance (or 15 grams per 1 ton).

If we are talking about volumetric concentrations(volume fractions, volume fractions), then 1 ppm is a cubic centimeter (aka milliliter) per cubic meter(cm 3 / m 3). Yes, concentration carbon dioxide(CO 2) in the Earth's atmosphere is about 380 ppm, which means that in every cubic meter of air 380 ml (about 2 glasses) is occupied by carbon dioxide.

Often, mg of a substance reduced to 1 m 3 of gas under normal conditions is also called ppm. This is only partly true, since the mass of 1 m 3 of air is almost equal to 1 kg. But this is completely wrong if this definition expanded by a cubic meter of arbitrary gas. It is also incorrect to consider ppm equal to mg per liter, which is partly true for aqueous solutions, but gives a large error when moving to hydrocarbons, the density of which is 0.5-1 kg/l.

At analysis of mixtures various gases in order to determine their qualitative and quantitative composition, use the following basic units of measurement:
- “mg/m3”;
- “ppm” or “million -1”;
- "% about. d.";
- “% NKPR”.

Mass concentration toxic substances and the maximum permissible concentration (MPC) of flammable gases is measured in “mg/m3”.
The unit of measurement “mg/m 3 ” (eng. “mass concentration”) is used to indicate the concentration of the measured substance in the air working area, atmosphere, as well as in exhaust gases, expressed in milligrams per cubic meter.
When performing gas analysis, end users typically convert gas concentration values ​​from “ppm” to “mg/m3” and vice versa. This can be done using our Gas Unit Calculator.

The parts per million of gases and various substances is a relative value and is denoted in “ppm” or “million -1”.
“ppm” (eng. “parts per million”) - a unit of measurement of the concentration of gases and other relative values, similar in meaning to ppm and percentage.
The unit "ppm" (million -1) is convenient to use for estimating small concentrations. One ppm is one part in 1,000,000 parts and has a value of 1×10 -6 of the base value.

The most common unit for measuring the concentrations of flammable substances in the air of the work area, as well as oxygen and carbon dioxide, is the volume fraction, which is denoted by the abbreviation “% vol. d." .
"% about. d." - is a value equal to the ratio of the volume of any substance in a gas mixture to the volume of the entire gas sample. The volume fraction of gas is usually expressed as a percentage (%).

“% LEL” (LEL - Low Explosion Level) - lower concentration limit of flame distribution, minimum fuel concentration explosive substance in a homogeneous mixture with an oxidizing environment in which an explosion is possible.

The pH value is a pH value that allows you to determine how many free hydrogen ions are contained in an aqueous solution. When various salts are dissolved in water, or, for example, when preparing a certain solution, the acid-base balance is disturbed, after which the pH must be measured.

At the same time, one should not confuse the parameters that determine the alkalinity and acidity of a solution with the pH indicator, since there is some difference between them, but many still do not notice this difference. The pH value actually determines the level of alkalinity and acidity of the solution, but the acidity and alkalinity of the solution already indicate the number of compounds contained in the solution and helping to neutralize the alkali or acid.

Flow rate chemical reactions directly depends on the pH level.

In hydroponics applications, pH control is very important. The influence of pH on plant development has both positive and negative effects. Since its uncontrolled change in any direction can lead to a lot of problems, and even to the death of the plant, which often happens.

IN Everyday life The pH concentration must be maintained within limits so that it does not affect the quality of the water. Thus, for drinking water The typical pH level is 6-9, while for solutions that are used in hydroponics, it usually ranges from 5.5 to 7.5.

Is there a need for systematic pH determination?

The pH of aqueous solutions plays a major role in determining the performance and properties of a hydroponic solution. After all, at an optimal pH level, plants easily absorb nutrients, which is so necessary for successful development and growth.

It is worth noting that with a reduced acidity pH, the solution acquires an unpleasant feature - corrosive activity. When the pH level is increased pH>11, the solution exhibits bad smell. It must be handled with particular care, as it can irritate the skin and eyes of a person.

It should also be clarified that there are no ideal and constant pH values. For individual species for plants it should be about 6.8 - 7.5, and for other crops - about 5.5 - 6.8.

pH control methods

There are several fairly common ways to control the pH factor: measuring pH using universal indicators: pH meter, pH strips, liquid pH test.

According to some experts, such a measurement method as pH test strips looks a little rough. It consists in the use of universal indicators, which are a mixture of several strips using dyes, the color of which depends directly on the acid-base environment: from red, slightly touching yellow, then green, blue and finally reaching purple. This kind of coloring occurs as a result of a transition from an acidic region to an alkaline region. No matter how universal this control method is, it has one significant drawback: the pH of the environment changes significantly if, for example, the solution has some color or is cloudy.

If you have chosen a pH meter as a method of monitoring the pH of aqueous solutions or the pH of soil (for example, or), in this case you can measure the pH level in the range from 0.01 to 14. As a result, you will receive more accurate information than in the case application of indicators.

The function of such a pH device is based on measuring the EMF of a galvanic circuit, which in its design has a glass electrode, the potential of which depends directly on the concentrated content of H+ ions in a particular solution. This method is very convenient, since the accuracy of the device directly depends on timely calibration. With this method, it is quite easy to determine the pH of the solution when it becomes cloudy or colored. Actually, thanks to this, this method is one of the most popular.

pH adjustment

To lower or increase the acidity of a hydroponic solution, use special pH lowering or pH increasing solutions. Be careful, it only takes a few drops per liter to change the solution.

Using pH Down and pH Up:

To shift the pH up or down, special solutions are used.

At the rate of 3 ml per 10 liters for a shift of 1 point up or down.

For example, your water pH is 4.0, and you need to raise it to 5.5. The following calculation is made:

5.5-4.0=1.5x3=4.5 ml pH UP per 10 liters of water.

The calculation is similar for pH DOWN

What is tds?

TDS, ppM, or pH of salts - the total content of salts in a solution

It is worth touching on the topic of mineralization. A process such as mineralization is the determination of the total amount of salts contained in a solution. Among the most common it should be noted inorganic salts. They can be chlorides, bicarbonates, sulfates of potassium, calcium, sodium, magnesium, this can also be the minimum number organic compounds, which dissolve in water.

In everyday understanding, this is the level of hardness and softness of water.

TDS measurement

To measure salt levels, the easiest way to purchase a salt meter is a digital TDS meter. This device determines the ppm of a solution in a matter of seconds.

TDS

In Europe, mineralization is usually called in two ways: and Total Dissolved Solids (TDS). This will be translated into Russian as the number of dissolved particles. The unit for determining the level of mineralization is 1 mg/liter. This is an equivalent parameter for the weight of all dissolved particles and elements in milligrams, namely salts, which are contained in a liter of solution.

ppM

The mineralization expression level can also be displayed in ppM. This abbreviation stands for parts per million, which translated into Russian means “parts per million,” that is, how many salt particles are dissolved in 1 million particles aqueous solution. A similar abbreviation can be found in some European sources. It looks like this: 1 mg/l = 1 ppm.

(ppm). To convert units of measurement mS/cm to ppm and vice versa, it is necessary to determine which conversion factor should be used. Typically, TDS meters use coefficients of 0.5, 0.64 or 0.7. Less commonly used is 1.0. Sometimes the device has a function for manually entering this coefficient.

*Note: 1 mS/cm = 1000 μS/cm

Coefficient of various devices

Manufacturer or device	Coefficient
,	0.5
	0.64
	0.70
	1.00

How to convert TDS (ppm) to EC (mS/cm) units yourself

To convert the unit of measure EC ( µS/cm) in TDS (ppm) a value in µS/cm multiply by the TDS meter coefficient (0.5, 0.7 or other).

To convert TDS (ppm) to EC ( µS/cm) it is necessary to divide the measured value by the coefficient of the TDS meter (0.5, 0.7 or other).

How to determine the conversion factor of a TDS meter

The conversion coefficient of a TDS meter can be determined if the device is also an EC meter. In such cases, for the same solution, it is necessary to measure mineralization (ppm) and electrical conductivity (µS/cm). Next, we divide the mineralization value (ppm) by the electrical conductivity value (μS/cm). The resulting number is the conversion factor of that TDS meter.