Any suitable humidity sensors for +125 degree C environment

Hi,

I have been looking for humidity sensors that can withstand 150C (doesn't have to be operating) for my project.

Normally the temperature is kept under 50C, once every while (once three months), the temp may go up to 150C.

I am considering using those "capacitive" sensors that can go up to 150C or 190C,

https://www.ist-ag.com/sites/default/files/DHP14-FemtoCap_E.pdf

https://shop.bb-sensors.com/out/media/Datasheet_Capacitive%20humdidty%20sensor_KFS140_TO_new.pdf

https://shop.bb-sensors.com/out/media/Datasheet_Capacitive_humidity_sensor_KFS140-D.pdf

I am looking for a sensor reader and a probe shell to protect the sensor. I know most PCBs or plastics cannot stand 120C, so I am going to have a reader board away from the hot area, use wire to connect to these sensors (like probe). Also, I am looking to use a metal probe shell.

Yet, I am unsure how to measure values off these sensors. I heard capacitance is not as simple as resistance reading...

Has anyone successfully done such thing or have an advice on how?

Any sensor board or probe shell recommendations?

Thanks a lot!

Talan

Is cost an issue ?

Electronics can be made to operate at 200C if the price is right - Google "downhole electronics).

I would suggest some detailed discussions with the supplier before committing to any of the sensors you suggest, to be sure that they can cope with the conditions.

The wet bulb technique would work fine, if you can cope with all the other issues.

My temperature cycler can do humidity and also reach 150C (not at the same time), the humidity sensor in it is two temperature sensors about 2cm apart, one of which has a little filter paper sock which is kept wet when measuring humidity.

There is a little water bath with a pump and depth sensor to keep the "sock" wet when needed.

MK

Thank you for the response Michael.

Cost is an issue, which I am trying to keep the total module to cost below 300 USD.

I am trying to build an incubator, so I am hoping the sensor can be space efficient too.

As others suggested, I am looking at https://shop.bb-sensors.com/out/media/Datasheet_Capacitive_humidity_sensor_KFS140-D.pdf

Where the sensor itself is pretty affordable, yet I am trying to figure out a good way to read value from this sensor.

So, I was hoping to attach a metal shell over the sensor, expose them to the chamber, and have the sensor connected to a reader board through wires.

Talan

You can put this kind of sensor at the end of a cable if you design the circuit with some care.

You need a circuit that can compensate for the cable capacitance which will be considerable (you will need a screened cable) and will vary with temperature.

Are you planning to build a lot of these ?

MK

You can put this kind of sensor at the end of a cable if you design the circuit with some care.

You need a circuit that can compensate for the cable capacitance which will be considerable (you will need a screened cable) and will vary with temperature.

Are you planning to build a lot of these ?

MK