Mq137 Ammonia Sensor

Using Arduino Sensors
1

Hello,

Does anybody have tried to get the mq137 work and show right measurements ? I am trying to make work this http://www.sainsmart.com/sainsmart-mq137-ammonia-detection-sensor-nh3-gas-sensor-module.html
without any progress. Anyone know something ? I know that i have to calibrate it but even this i think its difficult. I have made a known sollution of nh3 in the laboratory but i dont know how to use it

Thanks in advance

2

tsotos:
Hello,

Does anybody have tried to get the mq137 work and show right measurements ? I am trying to make work this SainSmart MQ137 Ammonia detection sensor NH3 Gas Sensor Module – SainSmart.com
without any progress. Anyone know something ? I know that i have to calibrate it but even this i think its difficult. I have made a known sollution of nh3 in the laboratory but i dont know how to use it

Thanks in advance

Well, since no one else has replied, I will and begin by asking to see the schematic of the circuit you have that is using the sensor. Did you let it cook for 48 hours before testing, as per the manual? You need to get everything operating before worrying about calibration.

I am sure you recall your chemistry class. Dissolve ammonia in water you get nh3oh. The sensor detects gas, not liquid. I guess you are going to use the ammonia coming from the nh3oh.

What kind of calibration are looking for? Can you control for temperature and atmospheric pressure?

Paul

3

hello,

I want to measure ammonia in the air (nh3) in a poultry farm. The problem is i cant find any sample code or library in the internet to get a right measure. Has anybody worked with this sensor ?

4

anyone ?

5

tsotos:
anyone ?

Where is your sense of adventure? Be a pioneer! You can be the official expert on ammonia sensors.

Paul

6

I am coming back to this topic cause i left it on side and i am trying to remake it. So I've bought this sensor. SainSmart MQ137 Ammonia detection sensor NH3 Gas Sensor Module – SainSmart.com
I apply this code to aduino.
void setup() {

Serial.begin(9600);
}

void loop() {
// read the input on analog pin 0:
int sensorValue = analogRead(A0);
// Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
float voltage = sensorValue * (5.0 / 1023.0);
// print out the value you read:
Serial.println(voltage);
}

and i get the output voltage of the sensor. When i put the sensor in an nh3 enviroment the output voltage change and get higher. The problem is how can i convert this reading to ppm. The datasheet of this sensor is this http://eph.ccs.miami.edu/precise/GasSensorSpecs/NH3.pdf
There is a logarithmic scale that converts the resistance of the sensor to ppm. So i think that i have to convert someway the output voltage to resistance. Am i wrong ? How can i do this ? Any help ?
Thanks in advance

7

Hello,
I used to use ammonia sensing electrodes in industrial settings.
The ammonia electrode is a simple beast and consists of a pH electrode as the base sensor, and a membrane to let ammonia gas get to the pH electrode.
The ammonia electrode is a sort of ISE (Ion Specific Electrode - pH electrode is an ISE specific to hydrogen ions).
Ammonia gas dissolves in water to form ammonium ions. You can reverse the reaction by making the water alkaline by adding sodium hydroxide.
If you are measuring ammonia in the atmosphere, you can skip the reversing step.
You need a small cap on the pH electrode (this assumes a conventional glass electrode). The idea is to fill the cap with an electrolyte, KCl Potasium Chloride.
You have a hole say 5-mm in the cap. You cover the cap with PTFE tape the same as plumbers use for seaing threads - thick or thin will do, thin responds faster.
If your sample is water, you add NaOH to the water. The ammonium ions go to ammonia gas, the gas permeates the PTFE membrane into the KCl, the KCl becomes alkaline and the pH electrode responds to the change.
You need to calibrate if you want accurate figures - the electrode is very simple, reliable and measures ammonia down to ppm levels.
If measuring ammonia in the atmosphere, you might need to dampen the PTFE.
There might be other ways to do it, but this electrode was the industry standard method.
For bomb-proof signal transmission, put a FET op amp as close to the electrode as possible (MAX407 was a good one, single sided supply, up to 10-years on a Lithium 3-V cell, no ground loop problems, no coax).

8

any other help ?

Thanks in advance