Hello, I am working on a project with MICS-6814 sensor.
Currently, I've got my thing up and running and voltages across the board seem to be ok except the mics sensor.
I was trying to measure the V_Rs value in "clean air" and see if the values would check out in the data sheet. So I fired up arduino and set up the pins. I read the value from ADC and converted it into Vref.
The voltage from the conversion was +- same as the the value I measured with my multimeter, so I can assume it was correct, however the value was about 2,98 V (from 3.3V Vcc) which is kinda high considering there is a top 1M resistor in the series divider. Anyway after figuring out resistance of the Rs through divider equation, the value of the resistor was out of the range of what it says in datasheet of the sensor (about 5M and 9M for CO2 and NH3).
Now the only sensor that seemed to be in range was NO2 sensor. The Rs value I calculated was 8,8k which seems to be in range.
After hours of trying to figure it out myself, I decided to come here and ask for help from someone who has experience with this kind of sensor. I am a beginner and it is very likely I've made a crucial error somewhere. Please help.
P.S. To make sure the images appear, I will also attach them to this post.
In fact, I've already read this post before. However, I went over my design again and I noticed that I might have screwed up the heating resistors for the mics sensor. Since I am using a Vcc of 3,3 V and not 5V, I calculated the resistor value for each sensor incorrectly (5 - VH) / IH where I should have used 3,3 V instead.. this means the sensor is probably not heating up correctly due to high value of resistance.
