I found the recommended operating condition of SHT85 is 5 - 60C, 20-80%, but I want to keep the humidity of the refrigerated container above 90%RH. Can I use SHT85 ? If I use SHT85, you can list elements for me to buy and SHT85 can operate well in the refrigerated container. Thank you.
Vào Th 6, 27 thg 10, 2023 vào lúc 22:43 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
After reading through the relevant information in the datasheet, it looks like extended exposure above 80% humidity (for > 60hrs) doesn’t harm it significantly, but its guaranteed accuracy drops to +3% from +/-1.8% until it is removed from that high humidity environment for some time. It does state that those “extreme conditions” might accelerate aging, but it does not define by how much. I would note that this accuracy loss is pretty much a universal phenomenon with MEMS-based humidity sensors, so switching to a different make will not avoid this issue. In particular, it is discussed on page 32 of the ENS210 datasheet.
The other concern, mentioned in note 5 on page 3 of the datasheet, is that condensation should be avoided to prevent corrosion and leakage currents on the pcb. To prevent this issue in your application, one might consider the use of conformal coating to protect the circuit board. If used, one would need to be especially careful to avoid covering the filter area on top of the sensor. If your application is only for relatively short-term lab experimentation, then the need for preventing corrosion is probably reduced, as this is typically a long-term problem.
Regarding other component needed, they give a diagram on page 8, which shows only two external resistors required for pull-ups on the I2C lines. It looks like they show 10K Ohm resistors.
It can handle any supply voltage between 2.15V and 5.5V, so it should be able to use the same supply as that required for your MCU.
Thank you. This first concern about the accuracy of the sensor, can I make a housing to protect it or use conformal coating to solve the problem ? Which option is the best for my application?
Vào Th 2, 30 thg 10, 2023 vào lúc 22:27 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
You can reply to me faster. I tend to buy the sensor during the week. Thank you. Regards
Vào Th 3, 31 thg 10, 2023 vào lúc 08:07 ĐỨC NGÔ MINH <duc.ngohacker@hcmut.edu.vn> đã viết:
Hi duc.ngohacker,
There is nothing you can do to improve the accuracy of the sensor when it spends extended time at high humidity (above 80% for more than 60 hours straight). It is inherent to the sensing material. Conformal coating would only protect the leads of the sensor from corrosion. You cannot coat the sensor itself or it will not be able to sense the humidity at all. A protective housing would only work if it prevented humidity from reaching the sensor, so that would not work either.
The only thing I can think of would be to physically remove the sensor from the high humidity environment between sensing readings. This would prevent the accuracy from getting worse as it would not have prolonged exposure to the > 80% environment. This is probably not a practical solution, but that’s the only thing I can think of at the moment.
Have other types of sensor that are suitable for my application?
Vào Th 3, 31 thg 10, 2023 vào lúc 20:15 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
I am not aware of any humidity sensors which do not exhibit this behavior of reduction in accuracy with long-term exposure to high humidity conditions. If you need better than 3% accuracy, you will have to do something to prevent the sensor from spending extended hours in that high humidity environment.
Besides removing the sensor from the environment between readings, I suppose it would be technically possible to design an enclosure to house the sensor within the larger environment. It would include a door which could be automatically opened for a few minutes to equalize humidity and temperature with the outer environment before taking a reading and then closed again. It might require a fan to speed up the equalization time. It would need to be somewhat sealed when closed and would need to include a heating element to raise the temperature inside the enclosure for the purpose of lowering the RH level to below 80%.
This solution would probably work if one could wait long enough between readings to allow the humidity level to drop for a sufficient length of time to prevent the high humidity from adversely affecting the sensor. The time required between readings could vary considerably, depending on the size of the enclosure, how well it was sealed, and how much heat was generated within the enclosure.
This seems like an extreme solution, but if you need less than 3% error, it is at least an idea.
This is a good idea. Thank you very much.
Vào Th 4, 1 thg 11, 2023 vào lúc 21:51 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
The position for sensor installation in the refrigerated container ? Thank you
Vào Th 5, 2 thg 11, 2023 vào lúc 07:47 ĐỨC NGÔ MINH <duc.ngohacker@hcmut.edu.vn> đã viết:
The best position for the sensor is a decision you would have to make, based on dimensions of the container, how you need to access and power the sensor, etc. I would also take into consideration the general airflow patterns of the container and try to find a position which would most likely reflect the average humidity and temperature of the container. I would avoid placing it near the location where the chilled air enters the container, as it would likely be cooler than average at that position.
As a preliminary step before installing your humidity sensor, you might try placing thermometers at various positions within the container and comparing their temperatures to see where the warmer and cooler spots are. This might also give you some idea of how uniform your temperature distribution is within the container, which I would think might be important to know.
Thank you very much. You said " It would need to be somewhat sealed when closed and would need to include a heating element to raise the temperature inside the enclosure for the purpose of lowering the RH level to below 80%". Can you recommend some heating elements suitable for my application ?
Vào Th 5, 2 thg 11, 2023 vào lúc 20:26 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
It would be hard to say which would be best because I don’t know enough about the specifics of your system to recommend a particular one, but here are some links to products that could possibly work for you:
Sparkfun pads
DFRobot Heating Elements
Riedon Heating Elements
I read datasheet, but I cannot find a way to control on/off status of heating elements.
Vào 05:11, T.6, 3 Th11, 2023 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
It would depend on which one was used. The DFRobot FIT0844 is self-regulating to roughly 40°C (see documentation here). It draws roughly 3W until it reaches that temperature and then will reduce power to maintain that temperature. The FIT0845 self-regulates to 100°C, so that would probably not work for you.
The others mentioned above would require reading the temperature of the environment (which you would have available from the humidity sensor) and turning on and off the heating element as necessary to control the temperature.
You can explain more because the datasheets don’t include this information.
Vào Th 6, 3 thg 11, 2023 vào lúc 22:21 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
Thạnk you.
Vào Th 7, 4 thg 11, 2023 vào lúc 07:00 ĐỨC NGÔ MINH <duc.ngohacker@hcmut.edu.vn> đã viết:
I am looking for a CO2 sensor with a resolution of 30 - 50ppm. I found SENSOR8_S3003V of ELT SENSOR CORP. and I don’t understand accuracy of its datasheet SENSOR8_S3003V “± 30ppm ± 3% of reading (1)(2)(3) (±300ppm ±3% of reading - 2%/3%/5% models)”. You can explain for me. Thank you. Regards.
Vào Th 7, 4 thg 11, 2023 vào lúc 07:00 ĐỨC NGÔ MINH <duc.ngohacker@hcmut.edu.vn> đã viết:
The accuracy is ±30ppm or ±300ppm.
Vào CN, 5 thg 11, 2023 vào lúc 23:15 ĐỨC NGÔ MINH <duc.ngohacker@hcmut.edu.vn> đã viết:
Hi duc.ngohacker,
I would not recommend the SENSOR8_S3003V, as it is not currently in stock, and may not be for some time. The T6713 or T6713-5K look like possible options. They have accuracy of ±25ppm and ±30ppm, respectively, or ±3% (whichever is greatest at any given reading). This means that for the T6713, its accuracy is 25ppm up to 833ppm, and from there and up it is ±3%. For the T6713-5K, its accuracy is 30ppm up to 1000ppm, and from there and up it is ±3%.
Actually, I want to measure the range of 0 - 2000ppm CO2. You can recommend some CO2 sensors. I found CO2 sensors on digikey, but I cannot find any suitable ones.
Vào Th 4, 8 thg 11, 2023 vào lúc 06:33 David_1528 via Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key <notifications@digikey.discoursemail.com> đã viết:
