CKAS-FLRS880热式气体质量流量计(CKAS-FLRS880Thermal gas mass flowmeter)

1、概述

1、Overview

 使用最好的产品是有效控制生产过程的必要保证。CKAS是热式质量流量计在工业领域应用的推广者，不断致力于将最新的技术应用于产品中，开发出了具有更高性能的优化产品，以合理的价格向用户提供准确、可靠的热式质量流量仪表，为用户提供最好的服务。

The use of the best products is a necessary guarantee for effective control of the production process. CKAS is the promoter of thermal mass flowmeter application in the industrial field. It is constantly committed to applying the latest technology to products, developing optimized products with higher performance, providing users with accurate and reliable thermal mass flowmeters at a reasonable price, and providing the best possible service for users.

2、产品特点

2. Product Features

2.1对气体流量测量无需温度和压力补偿，测量方便、准确，可得到气体的质量流量或者标准体积流量。

2.1 No temperature and pressure compensation is required for gas flow measurement. The measurement is convenient and accurate, and the mass flow velocity or standard volume flow velocity of gas can be obtained.

2.2宽量程比，达到100:1以上，可以用于气体检漏，特别在大管径、低流速、流量范围变化大及特小流量测量方面具有明显优势。

2.2 With a wide range ratio of more than 100:1, it can be used for gas leakage detection, especially with obvious advantages in  measurement of large pipe diameter, low flow velocity, large flow range change and extra-small flow.

2.3抗震性能良好，测量精度不受震动的影响。

2.3 The seismic performance is good, and the measurement accuracy is not affected by vibration.

2.4使用寿命长，传感器无活动部件和压力传感部件，安装简单，维护方便。

2.4 With long service life, the sensor has no moving parts and pressure sensing parts, and is easy to install and maintain.

2.5响应速度快，压力损失小，重复性好。

2.5 Fast response, low pressure loss and good repeatability.

2.6采用数字化设计，整体数字化电路测量，LCD显示直观清晰，测量准确。

2.6 Digital design, overall digital circuit measurement, intuitive and clear LCD display and accurate measurement

2.7配有RS485通讯模块或HART协议，配合上微机可实现集中管理。

2.7 Equipped with RS485 communication module or HART protocol, it can realize centralized management with microcomputer.

3、工作原理

3. Working Principle

3.1热扩散技术

3.1 Thermal diffusion technology

CKAS热式气体质量流量计采用的热扩散技术的传感元件包括两个带热套管保护的电阻式温度传感器(RTD)，测量气体时一个电阻式温度传感器(RTD)被加热，另一个电阻式温度传感器(参比RTD)用于测量气体温度。

The sensing element of the thermal diffusion technology adopted by the CKAS thermal gas mass flowmeter includes two RTDs with thermal sleeve protection. One RTD is heated when measuring the gas, and the other (reference RTD) is used to measure the gas temperature.

当传感器置于无流量的介质中时，由于加热器的作用将在两只(RTD)间形成一个温度差值(△T)。随着介质的流动基于热传导原理，介质分子将带走加热(RTD)上的部分热量，而参比RTD的温度将保持不变。加热温度传感器的功率(P)、 温度差值(△T)和气体质量流量(Q)存在如下函数关系：

When the sensor is placed in a medium without flow, a temperature difference (△T) will be formed between the two (RTDs) due to the action of the heater. As the flow of the medium is based on the principle of heat conduction, the medium molecules will take away part of the heat on the heated RTD, while the temperature of the reference RTD will remain unchanged. The power (P), temperature difference (△T) and gas mass flow (Q) of the heated RTD have the following functional relationship:

基于以上函数关系，按检测变量的不同可分为温度检测法和功率测量检测法。前者是指恒定加热温度传感器的功率(P)提供热量，测量随流量而变化的温度差值(△T),又称恒功率法；后者是指保持加热元件和被测流体温度差(△T)恒定，控制和测量加热温度传感器的功率(P),功率消耗随着流量增加而增大，称为恒温差法。

Based on the above functional relationship, it can be divided into temperature detection method and power measurement detection method according to different detection variables. The former refers to keeping the power (P) of the heated RTD constant to provide heat, and measuring the temperature difference (△T) that changes with the flow, also known as the constant power method; the latter refers to keeping the temperature difference (△T) between the heating element and the measured fluid constant, controlling and measuring the power (P) of the heated RTD, and the power consumption increases with the increase of the flow, which is called the constant temperature difference method.

热式气体质量流量计是利用传热原理，即流动中的流体与热源之间的热量交换关系来测量气体质量流量的仪表。按气体对检测原件的热源的热量作用可分为热分布式效应和热耗散效应。利用热耗散效应(金氏定律)的热式气体质量流量计，作为一种测量气体质量流量的直接式质量流量计以其压损低、流量范围大、高精度及高重复性、无可动部件等显著优点在国内外众多行业工业过程控制中得到了长足的发展和赢得了青睐。

Thermal gas mass flowmeter is an instrument that measures the mass flow of gas based on the principle of heat transfer, that is, the heat exchange relationship between the fluid in flow and the heat source. According to the heat effect of gas on the heat source of the detection element, it can be divided into thermal distribution effect and heat dissipation effect. The thermal gas mass flowmeter with heat dissipation effect (King's law) is a direct mass flowmeter for measuring gas mass flow, which has been greatly developed and favored in industrial process control in many industries at home and abroad due to its obvious advantages such as low pressure loss, large flow range, high accuracy, high repeatability and no movable parts.

3.2 恒温差法

3.2 Constant temperature difference method

恒温差法利用惠斯通电桥反馈电路控制加热温度传感器的功率来保持加热传温度感器和参比温度传感器之间的温差恒定。加热功率随着流量增加而增大，但是受到电路本身和电阻最大加热电流的影响，量程比得到制约；恒温差忽略了气体介质的温度变化，在介质温度变化较大的场合，气体的热流量系数和平衡常数的变化容易导致误差。

The constant temperature difference method uses a Wheatstone bridge feedback circuit to control the power of the heated RTD to keep the temperature difference between the heated RTD and the reference RTD constant. The heating power increases with the increase of flow, but is affected by the circuit itself and the maximum heating current of the resistor, and the range ratio is restricted; the constant temperature difference ignores the temperature change of the gas medium. In the case of large temperature change of the medium, the change of the heat flow coefficient and balance constant of the gas is easy to lead to errors.

3.3 响应时间

3.3 Response time

恒温差法(CTA)和恒功率法(CPA)的响应时间是完全不同的，如下图所示，(CPA)的响应时间取决于流体带走热量到其真实值的反应时间，而(CTA)则不同，基于恒温差的两个探头在流体变化时引起的变化，要求计算程序必须马上做出快速的响应。也因此提供了(CTA)的响应时间。

The response time of constant temperature difference method (CTA) and constant power method (CPA) is completely different, as shown in the following figure. The response time of CPA depends on the reaction time of the fluid to take away the heat to its true value, while the response time of CTA is different. Based on the changes caused by the two probes with constant temperature difference during fluid change, the calculation program must respond quickly. Therefore, the response time of CTA is provided.