Gas analyzers and units of measurement. Part per million What is ppm in production in simple words
Gas analyzer is a measuring device for determining 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 of a 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 volume concentrations (volume fractions, volume fractions), then 1 ppm is a cubic centimeter (aka milliliter) per cubic meter (cm 3 / m 3). Thus, the concentration of carbon dioxide (CO 2) in the Earth's atmosphere is about 380 ppm, and this 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 incorrect if this definition is expanded to 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 of 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”.
The mass concentration of toxic substances and the maximum permissible concentration (MPC) of flammable gases are 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 of the 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”) is a unit of measurement of the concentration of gases and other relative quantities, 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, the minimum concentration of a flammable explosive substance in a homogeneous mixture with an oxidizing environment at which an explosion is possible.
- PPMv(parts per million by volume) is a unit of concentration in ppm by volume. Those. the ratio of the volume fraction to everything (including this fraction). Naturally, for small values of concentration this value is equal to the ratio of the volume fraction to everything else without taking this fraction into account.
- ! This is the ratio of the partial pressure of water vapor in a gas mixture to the pressure of the dry mixture. For measuring small values of humidity in gases, this is the most common unit and in 99% of cases it is meant by a mysterious abbreviation PPM(=ppm).
- PPMw(parts per million by weight) is a unit of concentration in ppm by weight(sometimes they say “by weight”). Those. the ratio of the mass fraction to everything (including this fraction). Naturally, for small values of concentration this value is equal to the ratio of the weight fraction to everything else without taking into account this fraction.
- lim x→0 (x/(1-x):1/x)=1, i.e. for x→0 the ratio x/(1-x) → x;
- ! In relation to humidity, this is the ratio of the mass of water vapor in the gas mixture to the mass of the dry gas mixture.
- Likewise: PPB (parts per billion) is the unit of concentration in ppb = parts per billion. Figure it out there :)
How to convert ppm to mg/l?
- For solutions of something in water at 1 ppm w = 1 mg/l
- For all other cases, keep in mind that mg- this is, and l- . Be careful when crossing a hedgehog and a grass snake!
- Above is all the necessary data for translation :)
Note that in most cases, the undefined unit “PPM” is PPMv for gas mixtures, and PPMw for solutions and dry mixtures, although there is often a desire to give a black eye to the author of the text who used such a unit for fractional estimates without reservation. Be careful, because if you make a determination error, you may not even get within the order of the reliable value.
(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.
| EC meter | TDS meter | |||
|
(mS/cm) |
(µS/cm) |
0.5 ppm | 0.64 ppm | 0.70 ppm |
| 0.1 | 100 | 50 ppm | 64 ppm | 70 ppm |
| 0.2 | 200 | 100 ppm | 128 ppm | 140 ppm |
| 0.3 | 300 | 150 ppm | 192 ppm | 210 ppm |
| 0.4 | 400 | 200 ppm | 256 ppm | 280 ppm |
| 0.5 | 500 | 250 ppm | 320 ppm | 350 ppm |
| 0.6 | 600 | 300 ppm | 384 ppm | 420 ppm |
| 0.7 | 700 | 350 ppm | 448 ppm | 490 ppm |
| 0.8 | 800 | 400 ppm | 512 ppm | 560 ppm |
| 0.9 | 900 | 450 ppm | 576 ppm | 630 ppm |
| 1.0 | 1000 | 500 ppm | 640 ppm | 700 ppm |
| 1.1 | 1100 | 550 ppm | 704 ppm | 770 ppm |
| 1.2 | 1200 | 600 ppm | 768 ppm | 840 ppm |
| 1.3 | 1300 | 650 ppm | 832 ppm | 910 ppm |
| 1.4 | 1400 | 700 ppm | 896 ppm | 980 ppm |
| 1.5 | 1500 | 750 ppm | 960 ppm | 1050 ppm |
| 1.6 | 1600 | 800 ppm | 1024 ppm | 1120 ppm |
| 1.7 | 1700 | 850 ppm | 1088 ppm | 1190 ppm |
| 1.8 | 1800 | 900 ppm | 1152 ppm | 1260 ppm |
| 1.9 | 1900 | 950 ppm | 1216 ppm | 1330 ppm |
| 2.0 | 2000 | 1000 ppm | 1280 ppm | 1400 ppm |
| 2.1 | 2100 | 1050 ppm | 1334 ppm | 1470 ppm |
| 2.2 | 2200 | 1100 ppm | 1408 ppm | 1540 ppm |
| 2.3 | 2300 | 1150 ppm | 1472 ppm | 1610 ppm |
| 2.4 | 2400 | 1200 ppm | 1536 ppm | 1680 ppm |
| 2.5 | 2500 | 1250 ppm | 1600 ppm | 1750 ppm |
| 2.6 | 2600 | 1300 ppm | 1664 ppm | 1820 ppm |
| 2.7 | 2700 | 1350 ppm | 1728 ppm | 1890 ppm |
| 2.8 | 2800 | 1400 ppm | 1792 ppm | 1960 ppm |
| 2.9 | 2900 | 1450 ppm | 1856 ppm | 2030 ppm |
| 3.0 | 3000 | 1500 ppm | 1920 ppm | 2100 ppm |
| 3.1 | 3100 | 1550 ppm | 1984 ppm | 2170 ppm |
| 3.2 | 3200 | 1600 ppm | 2048 ppm | 2240 ppm |
*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.
Product defects are equally often expressed both as a 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 defective samples / 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.
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