The essential differences between EPC and AFC technologies in gas chromatograph are
1. Different meanings. EPC:electric pneumatic control (including pressure and flow); AFC:automatic flow control. These are two gas control methods commonly used in chromatography.
2. differences in control methods. EPC adopts electronic pressure control; EFC adopts electronic flow control. In the end, the best velocity ratio is obtained to achieve the best separation effect.
3. Advantages of separation mode. After the GC has a programmed temperature separation mode, the EPC program booster adds another mode separation mode to GC, which can be used alone or in combination. If they are used together, the GC separation ability will be more powerful and flexible.
automatic frequency control (AFC) is an automatic control method that keeps the output signal frequency in a definite relationship with a given frequency. The circuit that realizes this function is called AFC loop for short. AFC loop is mainly composed of frequency discriminator and controlled local oscillator. Most of the latter adopt voltage-controlled oscillators, which can keep the IF fi as stable as possible when the input signal frequency fc and the locally controlled oscillation frequency fi change. Extended data
There are many kinds of gas chromatographs with different functions, but their basic structures are similar. Gas chromatograph is generally composed of gas path system, sampling system, separation system (chromatographic column system), detection and temperature control system and recording system.
The gas pipeline system includes gas source, purification and drying pipe and carrier gas flow rate control and gasification device, which is a closed pipeline system with continuous carrier gas operation. Pure carrier gas with stable flow rate can be obtained by this system. Its air tightness, the accuracy of flow measurement and the stability of carrier gas flow rate are all important factors that affect the performance of gas chromatograph. < P > The sampling system uses different samplers according to the state of the sample. Micro-syringes are generally used to inject liquid samples. The gas sample is usually injected with a push-pull six-way valve or a rotary six-way valve provided by the chromatograph itself.
the separation system is the heart of the chromatograph. Its function is to separate the components in the sample. The separation system consists of a column chamber, a chromatographic column and a temperature control component. Among them, chromatographic column is the core component of chromatograph. There are two main types of chromatographic columns: packed column and capillary column (open column).
reference source: Baidu encyclopedia -afc
reference source: Baidu encyclopedia -EPC
reference source: Baidu encyclopedia-gas chromatograph.