Common knowledge of environmental testing equipment

1、 Preface: Although the environmental testing industry is a traditional industry and started relatively late in industries such as science, technology, and national defense in China, it has only been truly popularized in the past 20 years. Although there are currently no less than 300 production and sales companies of various scales nationwide, companies that truly understand and master the core and essence of their products. For users, the product seems to be a seller's market with many choices, but due to the lack of highly skilled users who understand the performance of the product, coupled with the so-called prepayment system in the industry's operation, the "sales waiting for production" model and other tricks, as well as dealers playing with technical indicators, the marketing history of domestic market trial products for many years is the blood and tears of users. Hehe, it's over! I work in the technical field and don't want to say much about other things, but what I really can't stand is that many sample technical solutions use indicator configurations to confuse customers and sales personnel. Unfortunately, new users have no way to learn, and it's not easy to buy expensive or poor products. They continue to grow in the process.

Therefore, I will provide some explanations of the indicators of some sample schemes based on my understanding, hoping to be useful to a wide range of users. Of course, there are many indicators for environmental testing, and each has its own advantages in terms of configuration and operation. If we want to have a more comprehensive discussion, we can publish textbooks. However, my personal abilities are limited and I dare not take risks. I can only provide a brief explanation of commonly used temperature and humidity indicators and commonly used configurations within my knowledge range, to help novice users get started.

2、 Performance indicator analysis

（1） Temperature index

1) Temperature range:

Refers to the maximum temperature that the product studio can tolerate and/or reach. It usually contains the concept of being able to control a constant value, which should be an extreme value that can operate stably for a relatively long time. The general temperature range includes extreme high temperature and extreme low temperature.

The temperature range of a pure high-temperature chamber is relatively simple, with low temperatures generally ranging from 10 to 50 ℃ at room temperature, and high temperatures at nominal temperatures such as 200, 300, and 400 ℃.

The maximum high temperature limit of high and low temperature chambers for European and American products is around+180 ℃, estimated to be due to the sealing material; The nominal temperature of Japanese and Taiwanese products is+150 ℃, which should be a reliable indicator that can generally meet the temperature field indicators (deviation, etc.); The nominal temperature of samples such as Galaxy Sida is+100 ℃, but the technical agreement can actually be signed at around+130 ℃, depending on the insulation material. Of course, according to user requirements, the majority of companies' technical agreement indicators can be signed in at+180 ℃, but whether extreme temperature tests can be conducted requires physical verification. My personal suggestion is that if not necessary, a high temperature of 130 ℃ is more suitable.

The ultimate low temperature is mainly determined by the refrigeration capacity and refrigeration method. Here, only the specifications of the mechanical compression refrigeration system configuration are introduced. The maximum capacity of single pole refrigeration is usually -45 ℃, and the general index is set at -40 ℃; The theoretical limit capacity of stacked refrigeration can reach -82 ℃, but considering that the cooling capacity below -70 ℃ is too small, the general indicator is set at -70 ℃. Due to the fact that some users do not need to use lower temperatures, most companies will introduce cost-effective -20 ℃ or even 0 ℃ specifications. As for the sample index of every 10 ℃ level for Taiwan funded enterprises, I think it is a commercial deception of the desktop industry, although there are still differences in technology

2) Temperature fluctuation

This indicator is also called temperature stability, which refers to the difference between the highest and lowest temperatures at any point in the workspace within a given time interval after controlling for temperature stability. There is a small difference here. 'workspace' is not a 'studio', but a space that is approximately 1/10 of the side length of the studio away from the box wall. This indicator assesses the control technology of the product.

The general standard requires indicators to be ≤ 1 ℃ or ± 0.5 ℃.

Some companies advertise their control technology with a nominal ± 0.2 ℃, but in reality, the temperature fluctuation during temperature testing cannot reach within ± 0.3 ℃, making it difficult to meet the requirements for temperature uniformity and deviation below; It will be difficult to maintain humidity stability if the temperature fluctuation during humidity testing cannot reach ± 0.1 ℃.

It should be noted that temperature stability indicators such as air aging test chambers also exist, but they are not the same concept.

3) Temperature uniformity

The old standard is called uniformity, and the new standard is called gradient. After the temperature stabilizes, the maximum difference between the average temperatures of any two points in the workspace at any time interval. This indicator can better assess the core technology of the product than the temperature deviation indicator below, so many companies deliberately hide this item in their samples and plans.

The general standard requires an index of ≤ 2 ℃

However, objectively speaking, it is not economical for users to maintain uniformity of ≤ 2 ℃ even at temperatures above 200 ℃ in pure high-temperature test chambers.

4) Temperature deviation

After the temperature stabilizes, the difference between the average temperature at the center of the workspace and the average temperature at other points in the workspace at any time interval. Although the new and old standards have the same definition and name for this indicator, the testing has changed. The new standards are more practical and stricter, but the assessment time is shorter.

The general standard requires an index of ± 2 ℃, and for pure high temperature test chambers above 200 ℃, the actual operating temperature requirement is ± 2% Celsius (℃).

The indicators of Taiwan funded enterprises do not include the temperature uniformity and temperature deviation referred to in mainland China. They approximate the temperature distribution uniformity, and the English words are also different. The sample indicators are ± 0.5 ℃, ± 1 ℃, ± 1.5 ℃, etc. I hope friends who are familiar with the logo can explain it.

5) Temperature change rate

This is an indicator for assessing product configuration capacity, and the forms provided by various companies are diverse, including heating and cooling speed, heating and cooling time, heating and cooling capacity, etc. The heating and cooling ranges are also not uniform. Of course, there are also plenty of tricks involved. China Reliability Network.

For users who do not have specific requirements for temperature changes, it is important to specify the time it takes to reach the extreme low temperature from room temperature. Although there may be some tricks (strictly speaking, it is professional), a difference of 3-5 minutes is not a big deal.

For tests that require temperature changes, the simplest way for users to order a test chamber is to first specify the load test when signing the technical agreement, and then list all indicators such as the volume, size, weight, basic material composition, and possible maximum heat generation of the test sample. The relevant test standards should also include the starting and ending temperature points and process description of the temperature change curve, so that the supplier has no loopholes to drill. Do not use sample indicators as protocol indicators, as the interpretation of sample indicators lies with the supplier. According to the newly revised national standard for temperature change rate testing, it is either empty load or can be calculated with a 20% discount (reminiscent of Hou Baolin's cross-talk selling cloth). Even non professionals such as Fuqi ACS find it very difficult to read sample indicators.

（2） Humidity index (the air humidity index for general industries is given in relative humidity)

1) Humidity range

The maximum humidity that the product studio can tolerate and/or achieve. Due to the correlation between humidity and temperature, the humidity range is a binary range. Therefore, each company's sample will produce a temperature and humidity coverage chart, which demonstrates the supplier's technical strength in temperature and humidity control, and of course, there are also quite a few Zhou tigers.

As a user, the main concern is whether the humidity points you need can be stable for a long time. There is no need to compare the coverage maps of various companies unless they cannot cover the humidity points you need. Generally, products equipped with cooling and dehumidification systems have a humidity range of less than 75% RH, and their humidity stability and coverage ability are better. For those with automatic control of the refrigeration system, there will be no phenomenon of temperature drift caused by long-term (in days) operation during high temperature and high humidity tests.

2) Humidity deviation

After the temperature and humidity stabilize, the difference between the average relative humidity at the center of the workspace and the average relative humidity at other points in the workspace at any time interval. Generally, the standard for mainland products only includes this indicator in terms of humidity.

This indicator * standard requires+2/-3% RH, usually marked as ± 3% RH. Due to the larger deviation in low humidity and the fact that the national standard does not include low humidity parts, there is an annotation of ± 5% RH (≤ 75% RH).

In fact, this is a comprehensive indicator, and if the product can meet this indicator within the coverage chart range, it can prove that the product's humidity control and configuration are appropriate.

（3） Other

1) Wind speed

Due to different loads, the average wind speed in the workspace varies, and the assessment indicators cannot provide quantitative explanations for actual tests unless required by the test standards, which generally do not need to be specifically stated.

2) Noise

If it is a high-temperature test chamber or a humid heat test chamber without a refrigeration system, this indicator can be ignored, and the product will not produce much noise during operation.

The general national standard stipulates that the noise level of a humid heat chamber is ≤ 75dB, and the noise level of a high and low temperature chamber is ≤ 80dB. This standard can only ensure that the human body can accept it, but cannot meet the requirements for office placement.