Liquid Flow Sensors Selection Guide Datasheet by Sensirion AG

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© Copyright Sensirion AG, Switzerland Version 4 1/4
Application Note Liquid Flow Sensors
Sensor Selection Guide
While all of Sensirion’s liquid flow sensors are based
on our unique CMOSens® technology, the broad
product portfolio ranges from stand alone flow meters
to highly integratable manifold mount components
and even single use sensors.
This guide aims to assist you in selecting the best fit
for your application.
The decision for the right sensor is typically driven by
the target flow rates and electrical interfaces, as well
as special use case requirements, like e.g. a need for
IPxx ingress protection. Further selection criteria
include the required pressure resistance and
chemical compatibility with the relevant fluids.
*Flow Meter or Evaluation Kit available
Figure 1: Sensors and their H2O Flow rates.
© Copyright Sensirion AG, Switzerland Version 4 2/4
1 Selection Process
The chapter below guides you through the necessary steps to identify the right sensor for your application and your current
development stage. The relevant criteria are flow rates, electrical interface and form factor. Following the identification of the
right sensor(s), compatibility checks regarding pressures and material compatibility have to be made.
1.1 Step 1: Flow Rates
Sensirion’s liquid flow sensors are calibrated up to a certain full scale flow rate and kits with full scale flow rates between 8
µl/min and 120 ml/min are available. Owing to the microthermal measurement principle, Sensirion’s liquid flow sensors have
excellent turn down ratios and offer exceptional performance below and up to the full scale flow rate. When using pulsating flow
sources, your absolute peak flow rate should sit below the full scale flow rate of the sensor of choice. We consider the absolute
peak flow rate to be the highest peak in your typical flow profile. A peristaltic pump set to a flow rate of 800 ul/min, for example,
will produce significantly higher peak flow rates to achieve the average flow rate of 800 ul/min.
Example: Your application requires the measurement of aqueous solutions at 250-800 µl/min. Using Figure 1, you identify the
SLI-1000, LG16-1000D and the LPG10-1000 as possible candidates. The following chapters will help in choosing the
correct sensor.
1.2 Step 2: Interface and Sensor Form Factor
Sensirion’s liquid flow sensors can be grouped into several categories. The categories mainly differ with regard to the electrical
interface, form factor, and the resulting characteristics.
1.2.1 Standalone Flow Meters
Standalone flow meters offer IPxx protection against dust and water ingress. They feature a standard circular 4-pin M8
electrical connector and have been designed for use with the SCC1 sensor interface cables. By combining the flow meter with
the suitable SCC1 cable, a 0 - 10 V analog voltage, 4 - 20 mA current loop, RS485, or USB interface is available.
With their rugged design, the standalone flow meters are ideally suited for industrial applications, laboratory setups and
All stand-alone flow meters are also available in a Flow Meter Kit, which contains the selected flow meter, the USB and 0-10 V
interface cables, a set of fluidic fittings, instructions for use, as well as a viewer and logging software.
1.2.2 OEM Sensors
OEM flow sensors are designed to be installed as an integral system component, inside an instrument. They offer reduced
protection and a simpler electrical connection at the benefit of smaller size and reduced cost. Sensirion’s OEM liquid flow
sensors come with the digital I2C interface.
1.2.3 Single Use Sensors
Single use sensors are designed for high quantity applications with drastically reduced costs in mind. While still offering all the
benefits and performance of CMOSens® technology but with a limited sensor lifetime, the simplified mechanical design and
electrical connection enables cost-effective single use applications.
Example: You would like to integrate the sensor in a production line tool to monitor dispenses using analog readout. The
SLI-1000 is therefore your sensor of choice. The IPxx protected housing means that minor spills are no issue and the
solid M8-cable connection to our analog interface cable is ideally suited for this industrial use case.
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1.3 Step 3: Pressures
Kits are available for sensors with maximum pressure ratings between 12 bar and 500 bar, with individual portfolio sensors
reaching 1200 bar. Please make sure that the sensor capillary is never subjected to pressures beyond their maximum pressure
rating, see the respective datasheets for details.
Example: In your application, the maximum pressure is 6 bar. You check the SLI-1000 sensor datasheet and notice that the
maximum operating pressure is 15 bar. Therefore, the SLI-1000 fits for your application regarding the pressure
1.4 Step 4: Chemical Compatibility
While the sensing element is never in direct contact with the measured liquid, some chemical restrictions may arise from the
wetted materials (fittings, seals and capillaries). Please see the datasheet of the sensor you have chosen for a list of the wetted
materials and ensure their compatibility with your application.
Example: Again, in the SLI-1000 datasheet, you check the wetted materials: Borosilicate glass, PEEK, and FEP. None of the
materials are expected to give issues with the aqueous solutions you intend to use in your application. So the SLI-
1000 looks like the ideal candidate for your application.
2 Start Testing
Flow Meter and/or Evaluation Kits:
To allow for straightforward testing and evaluation of our sensors, Flow Meter Kits or Evaluation Kits are available. The kits
typically include a sensor, interface cable(s) and software to get you started. Some kits include fitting materials as well.
If your sensor of choice does not have a kit available, choosing the Flow Meter Kit for the standalone flow meter
covering the same flow range (as marked in Fig. 1) will provide an excellent test vehicle to test the performance of
our sensor technology in your application.
Example: You have identified the SLI-1000 sensor as the ideal candidate for your application. In order to test it, you purchase
an SLI-1000 Flow Meter Kit from one of our distribution partners:
3 Further information
All our sensor families are available with calibrations for water. Some sensors are available with additional or alternative
calibrations, typically for isopropyl alcohol (2-propanol, IPA). This calibration will yield more accurate results and better linearity
if the main liquid components of your application are hydrocarbons such as oils, organic solvents or the like. Note that the flow
ranges for water and IPA on a specific sensor may be different. See the sensor’s datasheet for further details.
Customized Solutions
Many applications will be successful with our standard products and will benefit from the economies of scale of these. Some
applications however require customized solutions, where the characteristics listed in Fig. 1 above give an indication of the
possible degrees of freedom. Contact Sensirion for details.
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