Preheating MQ131 ozone sensor - necessary?

I understand that prior to using an MQ!31 ozone sensor, you need to preheat it for 24-48 hours, however I am unclear as to whether you have to preheat it for this length of time each and every time the sensor is used. Are you supposed to preheat the heating element for this length of time just once and then you’re able to take readings at any point thereafter or do you have to preheat it every time it’s used?

Here is a quote from one of the user manuals:

2.3 Long time storage The sensors resistance produce reversible drift if it’s stored for long time without electrify, this drift is related with storage conditions. Sensors should be stored in airproof without silicon gel bag with clean air. For the sensors with long time storage but no electrify, they need long aging time for stbility before using.

Not sure how long is "long time storage", maybe 24 hours? I'd say you only need to burn it in if you haven't used it at least a day or two.

Bearlover: I understand that prior to using an MQ!31 ozone sensor, you need to preheat it for 24-48 hours, however I am

Can you provide a link to that information please.

It sounds like the burn in time after extended storage to me , several months not in the packet. That sensor is supposed to have long lifetime although i have seen some which need replacement after 2 years use.

From the Chinglish description i would be suspicious of what it actually is , and how it performs.

EDIT

For burn in time i mean the required treatment prior to soldering, not sure though.

Some gas sensors do require the occasional extended pre heat time of about 5 mins occasionally , particularly for harsh use such as breathorlisers ETC.

For burn in time i mean the required treatment prior to soldering, not sure though.

Some gas sensors do require the occasional extended pre heat time of about 5 mins occasionally , particularly for harsh use such as breathorlisers ETC.

Clarification: "Burn-in" refers to powering/running the device for a given amount of time before using it's values, NOT actually heating it up in an oven or anything like that.

Boardburner2: Can you provide a link to that information please.

http://p.globalsources.com/IMAGES/PDT/SPEC/037/K1059654037.pdf

So I don't have to worry about preheating it after storing for say a week or two in a bag with silica gel?

Thanks for the help guys, I appreciate it.

Bearlover: So I don't have to worry about preheating it after storing for say a week or two in a bag with silica gel?

Portable units used occasionally normally require a 20 min warm up period each time they are turned on in order for the readings to stabilise.

EDIT That is for a unit specific to O3 though which uses adsorption spectra.

Your type of detector is similar to breathalyser types where 5 mins is enough for cleaning.

Manufacturers of these devices are guided by the specification but normally determine their own operating procedure by testing and calibration.

Your detector is sensitive to NOX as well, corona discharge generators using air will generate this also so this needs to be considered.

Thanks, that info is really useful.

I am actually using a corona discharge ozone generator. Do you by any chance know what proportion of the ozone gas produced by corona discharge is comprised of NOX gases?

Instead of using the term "pre-heating" I would use the term "stabilizing".

Every time you use this type of sensor (MOx or Metal OXide type sensors) you should wait until the sensor is "stabilized". The first time it can take several hours or even 1-2 days. If you use the sensor every day I would let it stabilize for at least 15 minutes before determining R0. If you use it once a week, at least 30 minutes.

This means that you put the sensor in clean air in the room where you will do the measurement and wait until the sensor resistance is stabilized. This stabilized resistance is called R0. R0 is dependent on temperature and humidity. By the way DON'T use pure nitrogen as clean air, these type of sensors NEED ~20% oxygen to work.

If you want to use this sensor outdoors where the temperature is very different then the storage temperature it can take longer to stabilize (15-20 minutes longer).

In short the best way is to follow the sensor resistance in time in clean air. If the value is steady over say 5-10 minutes then the sensor is stabilized. Also compare the new R0 with the Ro of the previous time you used the sensor, these values should be close. Over several months of use R0 can change. Keep track of R0 and how long it takes to get stable and build up experience of how long it will take to stabilize.

Be aware that this sensor is also sensitive to NO2 and other gases. The sensor will always measure the sum of all the gases it is senstive to. You can't differentiate what gas(es) the sensor reacts to.

Bearlover: Thanks, that info is really useful.

I am actually using a corona discharge ozone generator. Do you by any chance know what proportion of the ozone gas produced by corona discharge is comprised of NOX gases?

I do not know , it may be of variable proportions depending upon conditions.

I had a corona discharge unit with a claimed life of 10000 to 30000 hours.

By 5000 hours though output was about half.

Tarbo: Instead of using the term "pre-heating" I would use the term "stabilizing".

Every time you use this type of sensor (MOx or Metal OXide type sensors) you should wait until the sensor is "stabilized". The first time it can take several hours or even 1-2 days. If you use the sensor every day I would let it stabilize for at least 15 minutes before determining R0. If you use it once a week, at least 30 minutes.

This means that you put the sensor in clean air in the room where you will do the measurement and wait until the sensor resistance is stabilized. This stabilized resistance is called R0. R0 is dependent on temperature and humidity. By the way DON'T use pure nitrogen as clean air, these type of sensors NEED ~20% oxygen to work.

If you want to use this sensor outdoors where the temperature is very different then the storage temperature it can take longer to stabilize (15-20 minutes longer).

In short the best way is to follow the sensor resistance in time in clean air. If the value is steady over say 5-10 minutes then the sensor is stabilized. Also compare the new R0 with the Ro of the previous time you used the sensor, these values should be close. Over several months of use R0 can change. Keep track of R0 and how long it takes to get stable and build up experience of how long it will take to stabilize.

Be aware that this sensor is also sensitive to NO2 and other gases. The sensor will always measure the sum of all the gases it is senstive to. You can't differentiate what gas(es) the sensor reacts to.

I am using a MQ-137 sensor and I monitored my Ro value for 8 hrs. During the first 2 hrs the value was around 23k ohm and later after 8 hrs it dropped to 17K ohm. The value of RL is 47K ohm. What can I conclude from this? Should I wait longer since the datasheet says the pre-heat time is 48hrs?

Aswinth: I am using a MQ-137 sensor and I monitored my Ro value for 8 hrs. During the first 2 hrs the value was around 23k ohm and later after 8 hrs it dropped to 17K ohm. The value of RL is 47K ohm. What can I conclude from this? Should I wait longer since the datasheet says the pre-heat time is 48hrs?

48 hours may be excessive but it is manufacturers reccomendation.

You could graph Ro over time qand wait until the curve flattens out.

What type of electric supply is necessary for preheating PRE I guess - constant current or just 3.3V with enough amps?.

Any Idea what the RED pin would be? thanks a lot