connecting NH3 and CO sensors to PIC16F877A

[amindzo]

Hi,i want to connect ME3-NH3 and ME3-CO gas sensors to PIC16F877A,but their datasheets are not complete and not clear, i have sent a mail to company and they send me some more information but i don't think it's enough,could you tell me how can i connect them to PIC16F877A(hardware) and how can i write the code?
I use picbasic pro.

you can see their datasheets in this website:
http://www.hwsensor.com/English/prod...rochemical.htm

[skimask]

Hi,i want to connect ME3-NH3 and ME3-CO gas sensors to PIC16F877A,but their datasheets are not complete and not clear

Looks complete enough to me... Current ouput = gas concentration...

i have sent a mail to company and they send me some more information but i don't think it's enough

Ya...that'll work... NOT! Maybe if you were buying 1,000 of them.

could you tell me how can i connect them to PIC16F877A(hardware) and how can i write the code?

You can connect the output from the sensor to the '877A in the usual way and use the A/D inputs.
You can also write the code using a keyboard and a PC.

I use picbasic pro.

How often?

[amindzo]

which pins i should connect to PIC16F877A? what's the respect of the voltage value(that measure with A/D) and gas concentration?

[skimask]

which pins i should connect to PIC16F877A?

Pick one...

what's the respect of the voltage value(that measure with A/D) and gas concentration?

What voltage? It's a current output...

[amindzo]

Hi, i want to measure the CO and NH3 concentration and when it reaches to warning value then the PIC turn on the alarm and other things, with this application i think i can use MQ7 and MQ137 sensors, i attach you the application circuit of MQ series.
you can see MQ7 and MQ datasheets in this page:
http://www.hwsensor.com/English/prod...iconductor.htm

i think i should use MQ7 and MQ137 with this application, so i think i should use MQ series application circuit( that i attach you) and i can adjust the warning value with putting a potentiometer instead of red circled resistor in the picture(attached file) and turn it until adjust to warning value . am i right?
but how can i calibrate the sensors in clean air? how can i understand that the value of potentiometer reaches to the suitable value ?

[skimask]

http://www.hwsensor.com/English/prod...iconductor.htm

I can't see squat on that link...

i think i should use MQ7 and MQ137 with this application, so i think i should use MQ series application circuit( that i attach you) and i can adjust the warning value with putting a potentiometer instead of red circled resistor in the picture(attached file) and turn it until adjust to warning value . am i right?

Well, write some code and show us what you've got...

but how can i calibrate the sensors in clean air? how can i understand that the value of potentiometer reaches to the suitable value ?

Aye...there's the rub...gotta have something to bump your numbers against. Time to run down to your local Standards and Calibrations lab and see what they say.

[Archangel]

but how can i calibrate the sensors in clean air? how can i understand that the value of potentiometer reaches to the suitable value ?

Most likely you cannot, Smog Test machines use calibrated, calibration gases just for that purpose, that contain various different mixtures, for certain CO is one of them, you might check your local Smog Test Station for near empty cylinders they might sell to you, or buy from an automotive parts distributor. Otherwise you will be on the hook to buy from a standards lab supplier.