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The Danfoss AKS 4100/4100U is a sophisticated liquid level sensor engineered for a broad spectrum of refrigeration applications. This device leverages Time Domain Reflectometry (TDR), also known as Guided Microwave technology, to accurately measure liquid levels. Its design ensures reliable performance across various refrigerants and vessel types, including accumulators, receivers, and standpipes. The sensor provides a 2-wire, loop-powered 4-20 mA output signal, which is directly proportional to the refrigerant liquid level, facilitating seamless integration into existing control systems without the need for a separate transformer.
The core principle of the AKS 4100/4100U involves the emission of low-intensity, high-frequency electromagnetic pulses. These pulses, approximately 1 nanosecond in width, travel along a probe (either a wire or a coaxial cable) down to the liquid surface. Upon reaching the liquid, the pulses are reflected and guided back along the probe to the electronic converter. The converter then receives and analyzes these reflected signals, converting the time difference between the transmitted and received pulses into a precise liquid level reading. This method is highly effective because the speed of light in air, at which the pulses travel, is constant. The device's reference point, typically the flange facing, serves as the origin for distance measurements.
The sensor's performance is notably robust against various environmental and process conditions. Factors such as dust, foam, vapor, agitated surfaces, boiling surfaces, and changes in the liquid's density or dielectric constant (er) do not compromise its accuracy. This resilience is crucial in demanding industrial refrigeration environments where such disturbances are common. The AKS 4100/4100U is capable of detecting liquid levels as long as the dielectric constant of the liquid refrigerant is higher than 1.2.
For applications involving CO₂, the coaxial version of the AKS 4100/4100U is mandatory due to CO₂'s low dielectric constant (er, liquid > 1.3), which produces weaker reflections. The coaxial version is also recommended for all marine applications, regardless of the refrigerant type, to ensure optimal performance and reliability in challenging maritime conditions. The cable version, suitable for most other commonly used refrigerants like R717 (ammonia), HCFCs, and HFCs (where er, liquid > 5.6), is not to be used with CO₂ or in marine applications.
The sensor's output is a standard 4-20 mA signal, which can be scaled to represent distance, level, or percentage of output. This flexibility allows users to configure the output according to their specific monitoring and control requirements. The device also includes an error signal capability, providing high (22 mA) or low (3.6 mA) outputs in accordance with NAMUR NE 43 standards, indicating hardware problems, missing reference pulses, low voltage, or lost level detection.
The AKS 4100/4100U offers significant versatility in its application. The cable version can be adapted to any length within a range of 800 mm (31.5 in.) to 5000 mm (197 in.), making it suitable for various vessel sizes. This adaptability is achieved by simply cutting the stainless steel cable to the desired length. The coaxial version is available in predefined lengths, catering to specific installation needs. Both versions are available with two different mechanical process connections: G1 in. pipe thread (AKS 4100) with an aluminum gasket, and 3/4 in. NPT (AKS 4100U).
An optional HMI Service/Display unit enhances the user experience by providing an intuitive interface for commissioning and on-site setup. This unit supports multiple languages (English, German, French, Spanish) and both SI and US units, displaying measurements in mm, cm, m, ft, or in. The HMI allows users to easily configure parameters such as probe length, scaling for 4 mA and 20 mA outputs, and the dielectric constant of the refrigerant gas. The ability to input the dielectric constant of the refrigerant gas, especially when the temperature condition in the standpipe/vessel is known, significantly improves the accuracy of Top and Bottom Dead Zone values.
The quick setup procedure, guided by the HMI, simplifies the initial configuration process. Users can select the probe type (single cable or coaxial), enter the probe length, and define the 4 mA and 20 mA output scaling points. For CO₂ applications, it is mandatory to input the correct dielectric constant. The HMI also allows for forcing mA output for testing and calibration purposes, ensuring proper functionality before full deployment.
One of the notable maintenance advantages of the AKS 4100/4100U, particularly the cable version, is its resilience to oil accumulation. Oil accumulated at the bottom of a standpipe does not interfere with the liquid level signal. This eliminates the need to remove the sensor for cleaning after oil has been drained, thereby reducing downtime and maintenance efforts. This feature is especially beneficial in refrigeration systems where oil circulation is common.
The robust construction of the sensor, with an IP 66/67 enclosure rating (NEMA type 4X equivalent), ensures protection against dust and water ingress, contributing to its longevity and reliability in harsh industrial environments. The use of stainless steel for the coaxial segments and single cable, along with EPDM gaskets, provides excellent corrosion resistance and durability across a wide range of refrigerant temperatures and pressures.
The modular design, with a separate signal converter and probe, facilitates easier installation and potential replacement of components. The cable version, being compact and easy to handle, simplifies shipping, installation, and service. The HMI unit, which can be ordered separately, serves as a valuable tool for diagnostics and troubleshooting, allowing technicians to quickly identify and resolve issues by checking settings and monitoring device status. The ability to reset the device to factory settings provides a straightforward recovery option in case of misconfiguration.
General| Category | Accessories |
|---|---|
| Type | Pressure Switch |
| Product group | Pressure switches |
| Product Type | Pressure Switch |
| Brand | Danfoss |
| Model Number | 084H4505 |
| Switch Type | SPDT |
| Supply voltage [V] AC | 250 V AC |
| Connection Size | G 1/4 |
| Housing Material | Aluminium |
