Monitoring of oil concentration in a refrigeration cycle

Decades of experience have shown us that measurements during OCR research are often complex and complicated.
Sampling is often difficult or not possible at all. Therefore, the relationship between oil and refrigerant must be estimated by indirect methods.  

The aim is to find out how efficiently a refrigeration system works as a function of the oil concentration.
The information drawn from the measurements provide data on how the processes in the compressor are proceeding and when it is no longer operational.

To make the measurements as precise as possible, SensoTech has developed the inline solution LiquiSonic® OCR, which has unbeatable advantages.

What if the ratio between oil and refrigerant was known at all times and with high precision?
What if it were no longer necessary to take time-consuming samples to determine the oil/refrigerant ratio?

With LiquiSonic® OCR, comprehensive information about the refrigerant process is continuously available. The permanent knowledge of the concentration ensures optimal process control, while the fast approach to the optimal oil/refrigerant ratio reduces the adjustment time.

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Determining the optimal ratio of oil in refrigerant with LiquiSonic® OCR.

SensoTech makes it possible to have accurate knowledge of the concentration of compressor oil in refrigerant at any time. Accurate in-line measurements eliminate the need for time-consuming and error-prone sampling. Measured values are thus available at any time and are updated every second. 

High precision for oil condition monitoring in refrigerant

SensoTech emphasizes precise measured values during the oil concentration monitoring. The determination of oil concentration is based on pressure, temp and sound velocity measurements in the liquid refrigerant. This highly accurate measurement principle enables precise setting of the desired oil circulation rate.

Continuous determination of the oil concentration instead of punctual readings

The great advantage of online oil condition monitoring is the permanent availability of the measured values. The user has precise knowledge of the oil concentration at all times, because the data gets updated every second. Time-consuming adjustment of the oil concentration in the circuit is thus a thing of the past.

Using one refrigerant device for a wide range of refrigerants

SensoTech convinces with sustainable and comprehensive process solutions. In total, up to 32 product data sets (calculation models) can be stored in the controller. This makes it easy to monitor a wide range of refrigerants with the LiquiSonic® measuring technology. Decades of experience lead to almost no refrigerant that has not yet been measured by SesnoTech.

Selection of measured refrigerants

  • R134a
  • R407c
  • R410A
  • R744
  • R1234yf
  • R1234ze
  • R290 (Propan)
  • R1233zd (E)
  • R407A
  • R404A
  • R454-B
  • R454-C
  • R717 (Ammoniak)

Selection of measured compressor oils

  • D11
  • ND12
  • PAG
  • ACC-HV
  • POE 68

Integrated support for the analysis of oil in refrigerants

Many years of experience enable us to understand the processes precisely and to respond to customer requirements.

Always by your side:

specify the measuring task

The first step is to clarify the medium that is to be measured. In this process, SensoTech engineers check whether the combination of refrigerant and oil is already available in the existing database. If this is not the case, the feasibility is checked in the in-house laboratory.

clarification of specification

After the measurement task is clear, specifics are clarified. For example, whether special materials, installation variants or special accessories are required for monitoring int the refrigerant circuit. The LiquiSonic® OCR is developed for this application and already has a special measuring head and an adapter vessel. This equipment enables an easy integration into the refrigerant circuit.

installation qualification on site

If desired, SensoTech can support the entire process. During this process, our application engineers check that the measurement system is installed correctly and verify that the first measurements are taking place correctly.

regular education and training

For various applications, SensoTech offers additional webinars and training courses. This gives the operator the opportunity to get to know the measurement system in advance or to discover new functions afterwards.

provision of new data sets

The LiquiSonic® measuring system is not limited to a specific refrigerant or oil. Different refrigerants, such as the refrigerant R32 and R134a, are analyzed in the in-house SensoTech laboratory. The use of a different refrigerant at a later stage is not a problem. To do this, SensoTech simply calculates a new data set, loads it onto the controller and the oil content in the new refrigerant can be determined.

consultation for following projects

Any questions regarding our projects or further applications, the SensoTech team is available for advice.

Practical application example of already measured refrigerants

There are countless refrigerants in use worldwide. As a globally active company, SensoTech has already implemented countless projects with partners.


Oil circulation rate monitoring in refrigerant R410A

  • Mainly used in refrigerations, air conditioning systems and heat pump equipment in buildings
  • Accurate inline determination of oil concentration
  • Replacement for banned R22 systems

SensoTech refrigerant analysis for R1234yf

  • 357 times more climate friendly than other used refrigerants
  • Used in automotive air conditioning systems
  • Replacement for R134a in new cars
  • Efficient at higher temperatures

Measurement of oil in refrigerant R134a

  • is not allowed to be used in new cars within the EU, therefore often used outside of Europe
  • used in automotive air conditioning systems
  • R134a is a standard reference worldwide

FAQ on the concentration determination of the refrigerant oil

If there are any questions regarding the measurement of oil concentration in the refrigerant circuit or the measuring system LiquiSonic® OCR, the team of SensoTech is here to help.

Frequently asked questions:

Why is sampling to determine the concentration of the refrigerant-oil mixture problematic?

Taking a sample to determine the concentration is inaccurate and laborious because it interferes with the closed system. Generally, refrigerants evaporate as soon as they come into contact with air. Samples amount to approximately one liter. The analysis is carried out in the laboratory. The concentration of oil in refrigerant is only available after a considerable period of time and is, moreover, only a snapshot. The missing sample quantity ensures that the determined measured value does not reflect the current concentration. The system must first settle in again. Real-time inline monitoring is therefore preferable to sampling.

What is the purpose of oil in a refrigeration system?

The oil in the refrigeration system lubricates the compressor and ensures that it works smoothly and does not suffer any damage. Care must be taken to ensure the perfect mixing ratio of oil and refrigerant. The rule here is: as little oil as possible, but as much as necessary. Too much oil can reduce the cooling capacity.

What happens if there is too much oil in the AC system?

If there is too much oil in the AC system, the cooling capacity is reduced. This reduction causes the AC system to function only conditionally, i.e. more time is required until the desired cooling is achieved or even the desired temperature cannot be reached.

What kind of oil is used in the refrigerant?

There are a variety of combinations of oil and refrigerant used in different compressors. The exact type of oil depends entirely on the compressor manufacturer, as the respective compressors are only suitable for certain oils.

Can the refrigerant in the air conditioning system be exchanged for another?

While measurements can be made in any known refrigerant, not every refrigerant can be used in every air conditioner. If a refrigerant other than the previous one is used, it may attack and damage the compressor seals.


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Application report

Application report for monitoring the refrigerant circuit



Webinars on measuring oil concentration in refrigerants

We will show you how to efficiently monitor your process with LiquiSonic® and determine the optimal ratio between oil and refrigerant in record time.

Click here for more information about the webinar.