# Soil Moisture sensor unit

A group of schoolmates and I are using soil moisture sensors that we got from ‘Sgbotics’ for a school project. Once we plug in the sensor, data will start coming in. It will only show numbers and no unit. So if anyone knows what unit the sensor uses, could you please tell me? Thank you.

What does the data sheet of that sensor have to say about the output?

Normally you don't get units, just a value, which you can map to 0-100% where 0 = drier than the desert and 100% = quicksand.

They will give me numbers ranging from 200-900 so it cannot be percentage. sorry for not clarifying this earlier.

You still haven't posted information on the sensor.

CelineGoh: They will give me numbers ranging from 200-900 so it cannot be percentage.

wvmarle said "map to 0-100%", not that the sensor readings are initially in %.

CelineGoh: They will give me numbers ranging from 200-900 so it cannot be percentage. sorry for not clarifying this earlier.

You're just getting an ADC reading indicating the voltage where 0V is 0 and 5v is 1023. You have to look at the datasheet for the sensor you have to see how they say to convert that voltage to a reading. When you do that math, the units will depend on how you do it.

Yes, those numbers sound very much like an ADC reading. So for your sensor 200 = 0% and 900 = 100% (or the other way around?). Now it's basic math to turn that into a percentage, assuming it's linear. You'll have to do some calibration, by measuring a number of known soil humidities.