FS1025-DL less sensitive and then stopped reporting flow

Question

Hello, 
 
 I have been testing out the FS1025-DL and it was working very well in our seawater system. But it appears to have failed, a few weeks ago the flow started drifting lower and now it reads zero, after taking it apart it appears that there is some corrosion. I was not aware sensor contacted the fluid.

Can you look at these photos and advise? Perhaps my application is not suited for this sensor, which is fine.

IK_Renesas · Answer

Hi Andy, 
 Thanks for your feedback. 
 First of all let me inform you that FS1025-DL is almost an EOL product, here you will see that the obsolete date is 4/25/2025 and we do not suggest any other product for replacement and as far I know we do not plan to release any new liquid flow sensors to replace the old and discontinued liquid flow sensors (at least until the end of 2024). 
 www.renesas.com/.../plc-240001-end-life-eol-process-select-part-numbers

Now regarding the damage on the sensor I would suggest first to do a test and see how the sensor is behaving to finally come to some conclusions about if it is damaged or not. 
 According the datasheet here is the analog output voltage of the sensor pin when no flow is passed through the sensor the output voltage is 0.5 V.

So when not passing flow to the sensor and you add a multimeter to measure the voltage on pin 3 check what is the voltage measured and let us know. 
 
 Also please make sure that your liquid flows into the correct direction. It should flow from input P1 to P2 output as shown in the screenshot above. 
 
 Please make this test and provide us feedback to do later further analysis on what causes issues to your sensor element. 
 
 Thank you. 
 Best Regards, 
 IK

raja · Answer

Hi Andy, 
 Thanks for the request. The sensing element itself is Parylene C coated + silicon carbide coating. The inner chamber of, for example, the FS1025-DL is made out of silicone and PPE+PS resin blend. So, it should measure the flow of sea water (if PH level lies below 8). 
 By seeing this pic, it looks like our sensor has been damaged. For further investigation, I need some more information. 
 1. How long did you test our sensor? 
 2. Please share the pic of your test setup. 
 I have attached application note that describes the factors that can affect our flow sensors. 
 https://www.renesas.com/us/en/document/apn/factors-influencing-accuracy-thermal-flow-sensors?r=1489456 
 Note: In general, we recommend non-aggressive chemicals and liquids within the pH level 4 to 8, with the parylene coated modules. Most coolants are fine as long as the system they used in does not form coagulants (water impurities, salt, etc).

Regards: 
 Raja.

FS1025-DL less sensitive and then stopped reporting flow

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