TIDA-01465: TIDA-01465

Dear customer,

Thanks for the question. You can refer to below link for reference. I would say 20-25pF change would be difficult. The only way is to increase the sensor plate. 

http://e2e.ti.com/blogs_/b/industrial_strength/archive/2018/03/01/accurate-frost-or-ice-detection-based-on-capacitive-sensing

Why do you need so big capacitance change?

Thanks

Hi Richard, 

Thanks for your input.

As per our observation, we have seen only 2-3 pF change when the frost thickness is 2mm. Since we have to take into account only 2.0mm frost thickness therefore we need to increase the range for small frost thickness (0.5 to 1.5mm) also.

Even though we have increase sensor plate area from 225sqcm(15*15) , 289(17 x17) and 400sqcm(20*20). We have seen the total delta change from 3.0pf, 5.0pF and  7.0pf change respectively. But this change is observe only during significant frost formation < 2.0mm. Only with 400sqcm electrode plate we have seen the delta capacitance for 2mm frost is approx. 3.0 to 4.0pf Change. For other plate same delta change is around 1-2pF only.

Kindly also help us to know how to decide the size and location of electrode in cabinet.  Is there any thumb rule. Currently we are placing the electrode at inlet of evaporator where we see the significant frost formation.

Please let me know your email id so that i can share you test result for more information on the same.

Best Regards,

Rajesh Sharma