## MQ2 Gas Sensor - Calucation of Rs

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bert.carremans
Pre-kindergarten
Posts: 2
Joined: Mon Dec 31, 2018 8:31 pm

### MQ2 Gas Sensor - Calucation of Rs

Hi,

on the product page for the MQ2 gas sensorhttp://wiki.seeedstudio.com/Grove-Gas_Sensor-MQ2/, the following formula to calculate RS_gas is displayed.
RS_gas = (5.0-sensor_volt)/sensor_volt; // omit * RL
When I apply Ohm's Law, the formula to calculate RS_gas should be RL * (Vc - VS)/VRL.
So why is the multiplication with RL omitted? Is RL equal to 1?

Thanks for your help!

designnotes.com
Pre-kindergarten
Posts: 10
Joined: Mon Jan 28, 2019 11:08 pm
Location: Philadelphia, PA
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### Re: MQ2 Gas Sensor - Calucation of Rs

Hi,

Welcome to the forum. Basically RL is (Load Resistance) and it is used to compute air resistance. As in the code it is considering that sensor is placed in the clean atmosphere that's why RL is considered to be 1.

Reference: float RS_air; // Get the value of RS via in a clear air
RS_air = (5.0-sensor_volt)/sensor_volt; // omit * RL

I hope it will help you.

Thank you.