Humidity design requirements

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I have to design a electronics device that is specified for environmental operating conditions of 0°C to 60°C with 5% to 95% relative humidity (non condensing).

I think the temperature part should be covered with commercial component selection (0°-70° operating temp.), but what about the humidity requirement?

• Is this humidity specification hard to achieve?
• Do I need to protect the PCBA with conformal coating?
• What are the general recommendations for different humidity specifications?

Of course I will need to perform some tests in the climate chamber. But I think there should exist some general guidelines for the design regarding humidity?specificationshumidityconformal-coatingShareEditFollowFlagasked 1 hour agoStefan Wyss5,24911 gold badge66 silver badges1818 bronze badges

• 1What do you mean by non condensing? I don’t think conformal coating would be adequate. – K H 1 hour ago
• 2I have often seen this “non condensing” addition to relative humidity specifications. I think it means that when you perform tests in the climate chamber, you need to carefully control the climate in order not to reach the dew point. – Stefan Wyss 1 hour ago 
• Well, you can easily find a cheapy commercial humidity sensor chip, and copycat its spec. Eg, (1) HDS1080 [0% to 100% relative humidity (Fig 2, 14 bit, 2~4% accuracy )] from TI:ti.com/lit/ds/symlink/… – tlfong01 1 hour ago    
• 1If you have high impedance analogue and sensitive circuits, at around 0 degC, water will collect on PCB surfaces if there’s humidity. So, I’d be tempted to ensure it works down to -10 degC and see what happens when you gradually warm it up through 0 degC. – Andy aka 45 mins ago
• 1@Andyaka Thanks for your comment. I have no high impedance analogue and sensitive circuits. It is mainly a digital device. Why do you think that 0°C will be special in term of humidity? When I look at a psychrometric chart, I see no differences to other other temp. ranges. – Stefan Wyss 24 mins ago 
• I don’t understand the difference between condensing and non condensing, but condensing modules are dirt cheap. (1) HR202 Sensor HDS10 Condensation Sensor Humidity Sensitive Module High Humidity Sensitive US$0.30 nl.aliexpress.com/item/… / ton continue, … – tlfong01 21 mins ago    
• / continue, … (2) Humidity Sensor Module HR202 Humidity Module Humidity Detection – US$0.5 nl.aliexpress.com/item/… – tlfong01 20 mins ago   
• Actually I even forgot the difference between H and RH. Of course Google is my friend: (3) Choosing a Humidity Sensor: A Review of Three Technologies – Denes K. Roveti 2001jul01 fierceelectronics.com/components/…. Now I understand everything, including that the US$0.5 toy understands the First and Second Law of Thermodynamics and has a built in EEPROM with equations to do the RH calculations. – tlfong01 2 mins ago    Edit   Delete

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