***** Sad to hear. I would happily pay for it in a Kickstarter/Indiegogo(...) campaign or alike! Props to you for a fantastic piece of technology, though!
Learn something new about Australia every time Dave puts a video out. Today, I learned how they pronounce “dosimeter” and “Americium” (i.e. not doe-SIM-uh-ter and am-uh-RISH-ee-um). Cool video and cool device!
i think it can be embedded to every phones, plus phones can record stats gps+radiations and then send it to google server, so we can build radiation map and
I like the idea of it - but the case leaves...much to be desired. I can imagine easily dropping or loosing this thing very easily on the ground or in a backpack. Give it some decals, a wristband loop, and maybe an optionally larger case for improved battery/storage.
If it really can only store that little data, maybe a SD-card slot would be good? Dumping the data once a day would be enough and keeps the powerconsumption down so it still runs a long time, yet provide enough space for months or more. With a 1GB SD card it should have enough space for 4 yeas or more worth of data.
***** The card draws 0 power when not powered. there is no reason to use it the whole day, but only to dump the data once per day from the internal storage.
***** Was just an idea, maybe somebody else will try to make a change to incorporate it. But 55 days is more than enough. it just seemed like the internal storage might not have been that big, and SD-card support ain't that hard to do as far as i have witnessed with some friends projects. (and with 1 Gb you could log about everything you want, and if it only would be battery-voltage, temperature and what not :P )
I guess it only has sufficient internal memory to store 7 days worth of results. It would be cool if it had a micro USB drive to enable you to expand the memory to store more days.
***** stMicro does great work with low power applications -- I'm guessing its ideal because the tube outputs pulses which can interrupt the sleep for each count then go back to sleep. If it had to stay awake and listen for pulses it would die in a day.
As an amateur particle scientist I like this. This has a muller tube that seems to only be gamma sensitive. Good enough for a dosimeter but I like to be able to measure alpha -- Your Americium 241 is a alpha source and it really sends my dosimeter into a frenzy.
Dave I think you picked the last week option and downloaded only that data. From what I get of Russian the options in the program under the small graph are: year, month, week, day.
My first thought when I saw the size of that adorable little GM tube was "fat chance ever finding one of those again," but I put SBM-10 into google, and there was a guy selling them on ebay for US$15 a piece. It appears the SBM-21 is the exact same tube, so that opens up more pools of availability. What would be the best is if someone could do organize a group-buy and spin up a bunch of those boards, because that and the case seem like the most time-consuming and difficult parts. Also I'm not sure what it is, but it seems a lot of the geiger counters in Russia use Roentgens, where everywhere else uses microsieverts. I personally prefer the Roentgen because I like the word. It's outdated and not used very frequently, but unless you're doing scientific datalogging, all you really need to know is bigger number==more bad
Mark Jordan the signal path and eevblog could learn a thing or two from ben krasnow of 'Applied Science'. that guy is a true engineer -- he can actually put his knowledge to use. eevblog and the signal path is basically just unboxings and teardowns of different equipment. cool, you can take things apart... but can you build anything? dave's uCurrent thing was embarrassingly simple for a veteran electrical engineer. if you haven't watched Applied Science yet, please do. that guy does truly amazing things in his garage, and he's very sincere and soft spoken, unlike dave who rattles off a bunch of 'catchphrases' and drives everybody crazy with his annoying upward inflection and throat phlegm.
As far as i understand it a small amount of material leaked into the Pacific but so little that its hardly worth mentioning. Keep in mind i am no expert , but all the things you read about radioactive seaweed and contaminated beaches in the US are total bullshit. Modern reactors like this one are very safe and have both inner and outer containment. The explosion you have seen on the news was only the outer containment getting blown off by a hydrogen oxygen explosion. This is not a dodgy 80s Russian reactor we are taking about that had no containment at all save for the reactor shielding
friendofCHAKA You are vastly overestimating the amount of contamination and vastly underestimating how huge the ocean is. Any contaminated water is so diluted that the change is practically undetectable by the time it reaches the US.
shodtech Действительно очень серьезная работа над энергопотреблением и миниатюризацией. И разработка платы в Altium- признак мастерства. Замечательный девайс! А насчет kickstarter - это очень перспективно, и есть люди, через которых можно запустить проект из наших стран бывшего СССР.
@EEVblog Americium is an alpha emitter. The muller tube thats in there isn't able to pick up alpha radiation unfortunately so you can't test your souce. Muller pancake style tubes with mica windows are what you want if you want to detect alpha. Cheers.
Eh isn't the "window" at the front og the geiger tube? So placing it on top of the radiation source will give a smaller reading than pointing the end at it. But love the design and video.
Another small detector is the K8 Nuke SafeGuard that only has three small LEDs and goes beep. And powered by a CR2032 button battery. May come in handy if some Middle East country violates its agreement. Have you been to the Uranium mines ? Do you have any Thorium deposits for building safe reactors for the third world countries ? Thank you for a great video that is much needed ! Only seventy (70) years since Trinity Test (16 July 1945 05:29:45 AM). Eyes UP and lights down, tjl Sent by Win7Pro64 w/ADSL
You have a weird saying "Too easy" - what does it mean? That the schematic is easy to read/understand or that the parts are easy to connect or ... Just found your channel - Excellent videos! Thanks
Does anyone know if there is a kit version of this already? It,s an amasing devise and project. Would realy like to have one. With fukushima going on. I am very worried. Greetz marco
+ShinTsu I wouldn't say good or bad. Sure, if the radiation is very low, the chance that the little tube is hit by a gamma "particle" is also very small. But it's all about probability, so you just count for a little longer (maybe a minute instead of seconds) and calculate the radiation level from there.
Sorry, but no. You can't just convert Röntgen into Sievert, they are not the same thing. The former is used to measure ionization (it is a legacy unit though) while the latter describes energy deposited (while taking the different biological effects of the different kinds or radiation into account). If any dosimeter ever displays any Sieverts to you, there will be a particular assumption built into the logic of the device. You can never be sure if the reading is correct. (Not without additional methods of measurement anyway.)
EEVblog you still have that online geiger counter? maybe put both into the same place and measure for a day and compare if both more or less agree on the value. I have had bad experiences with these tiny tubes to not be sensitive enough for serious use.
Hi mate. That is a very nice little dosimeter, well done Trot skies. Strange that the display is in English, but the software is in Russian. Unfortunately, it has been overtaken by the Chinese. Yesterday I was at Jay-car, a local electronics store, and they are selling a sort of dongle, that can be put into an IPhone. The thing was as big as 3-4 match stick held together. Grant you, not a stand alone unit, but much smaller never the less. Marcel.
Seems this project have been abandoned. The link to the creator's web page does not work and there are no commitments to the project since 2015. Shame... It was a nice gadget while it lasted.
Sure makes you wonder how the astronauts managed to safely pass through the concentrated radiation of the van allen belt and the general cosmic radiation on the trip to and from the moon and the suface radiation on the moon.
Gromitdog1 actually no. even thought the radiation is higher than on earth its still quite low. the dose they got is only like a few times (apollo 17 9mSv) the anual dose (2mSv) we get from backround radiation. Its not that the van allen belt is a death zone. its just a myth. with only 3mm of aluminum the PEAK rate is 200 mSv/h. with the speed they traveled they passed the belt within a few mins.
Sieverts. Ugh. Did you know that it is a computed value based partly on the tissues involved and the source [x-ray, gamma, neutrons...] of the radiation? A radiation dose that scored 1 sievert for bones might score over 100 for the eyes or brain. Some tissues are far more sensitive than others, and so get higher sievert scores. I get the way the unit is used as a composite biological equivalent, but I just felt like being that guy.
I guess it is pondered for an average whole body exposure of radiation. People do not usually get a focalised beam of radiation to one specific part of the body. Unless there are undergoing single beam stereotactic radiation therapy.
EEVblog Depends on the location of course. It's funny because one of AU's chief exports is uranium. Though as an alpha emitter with a fairly tame decay chain, it doesn't contribute that much. Main problem from it may tend to be radon buildup, which can be an issue in certain AU homes. Still, "traveling by motor vehicle" usually comes in at regularly higher risk than most of this stuff.
therealpanse Well I mean of course. Would you really take an electrical engineer and give him electrical products that basically say "you can do nothing yourself, you must have our proprietary everything, give yourself to the Apple Store cult fully"? He'd probably rather build his own smartphone.
+Sjoerd van Gestel A common view in Russia.I made for themselves, as a hobby. Production is not planned, because selling is bad, unworthy of the engineer. If you only knew how many ingenious designs vanished in boxes of these masters and remained unknown to anyone except the author and his friends.
***** thanks for info, I found link, try to put myself: ftp@://www.@радиокружок.n@et/%D0%94%D0%BE%D0%B7%D0%B8%D0%BC%D0%B5%D1%82%D1%80%D1%8B_%D0%9C%D0%B8%D0%BA%D1%80%D0%BE%D0%BD/%D0%A3%D0%BB%D1%8C%D1%82%D1%80%D0%B0-%D0%BC%D0%B8%D0%BA%D1%80%D0%BE%D0%BD/ Remove three "@"
Cool Video. Will someone please mass produce these? Please?
Knowledge = Performance +1 Me. Want. Now!
***** Same.
***** Sad to hear. I would happily pay for it in a Kickstarter/Indiegogo(...) campaign or alike! Props to you for a fantastic piece of technology, though!
Ok thanks. I would love to own one but I am also too lazy to make one myself.
Thanks! I think many people including myself will like it if you do decide to manufacture them!
поймать вас в следующий раз))) Nice, Dave)
This is an awesome dosimeter! Outstanding build!
Learn something new about Australia every time Dave puts a video out. Today, I learned how they pronounce “dosimeter” and “Americium” (i.e. not doe-SIM-uh-ter and am-uh-RISH-ee-um).
Cool video and cool device!
i think it can be embedded to every phones, plus phones can record stats gps+radiations and then send it to google server, so we can build radiation map and
+Konstantin Kuzminykh
.. every phone also needs a thermal cam with autofocus lens and laser scanner for 3d scanning
i think phone camera ccds can already do that crudely
Very nice dosimeter. I would love one.
I like the idea of it - but the case leaves...much to be desired. I can imagine easily dropping or loosing this thing very easily on the ground or in a backpack. Give it some decals, a wristband loop, and maybe an optionally larger case for improved battery/storage.
Michael Norman Prototype
Say it with me
Hail to my compatriot colleagues! Amazing work!
And, Dave, this 'поймать вас в следующий раз' thing is... insane!)
Whoah... Creepy)
Wow that's a nice unit. That lcd display is very sharp. Thanks for sharing.
What a great size. I wish these were commercially available
If it really can only store that little data, maybe a SD-card slot would be good?
Dumping the data once a day would be enough and keeps the powerconsumption down so it still runs a long time, yet provide enough space for months or more.
With a 1GB SD card it should have enough space for 4 yeas or more worth of data.
***** The card draws 0 power when not powered. there is no reason to use it the whole day, but only to dump the data once per day from the internal storage.
***** Was just an idea, maybe somebody else will try to make a change to incorporate it.
But 55 days is more than enough. it just seemed like the internal storage might not have been that big, and SD-card support ain't that hard to do as far as i have witnessed with some friends projects.
(and with 1 Gb you could log about everything you want, and if it only would be battery-voltage, temperature and what not :P )
ABaumstumpf Yes, even in tables, or some ASCI "interface" when we don't have PC soft, and we want read some data on smartphone outdoor. :D
I guess it only has sufficient internal memory to store 7 days worth of results. It would be cool if it had a micro USB drive to enable you to expand the memory to store more days.
What a nice project ... really nice.
Did this become a kit?
I wonder how long before I would have discovered this device on my own.
Thanks Dave
Wow, if this thing can really run for month on a single battery charge than the guy really knew what he was doing!
***** stMicro does great work with low power applications -- I'm guessing its ideal because the tube outputs pulses which can interrupt the sleep for each count then go back to sleep. If it had to stay awake and listen for pulses it would die in a day.
As an amateur particle scientist I like this.
This has a muller tube that seems to only be gamma sensitive. Good enough for a dosimeter but I like to be able to measure alpha -- Your Americium 241 is a alpha source and it really sends my dosimeter into a frenzy.
Dave I think you picked the last week option and downloaded only that data. From what I get of Russian the options in the program under the small graph are: year, month, week, day.
Very cool!
Поймать вас в следующий раз, literally means "(to) catch you next time" LOL
I would love one of these.
Very cool, good review, thanks for sharing ...
Enjoying all your videos! Be well!
EEVblog the link in the description is 404'ing (for the tube data) it looks like the link got copied twice?
***** yep
My first thought when I saw the size of that adorable little GM tube was "fat chance ever finding one of those again," but I put SBM-10 into google, and there was a guy selling them on ebay for US$15 a piece. It appears the SBM-21 is the exact same tube, so that opens up more pools of availability.
What would be the best is if someone could do organize a group-buy and spin up a bunch of those boards, because that and the case seem like the most time-consuming and difficult parts.
Also I'm not sure what it is, but it seems a lot of the geiger counters in Russia use Roentgens, where everywhere else uses microsieverts. I personally prefer the Roentgen because I like the word. It's outdated and not used very frequently, but unless you're doing scientific datalogging, all you really need to know is bigger number==more bad
If you signal path and w2aew could put out a video per day I would cancel directv. Always a great video Dave, thanks
Mark Jordan i love casting some youtube channels to the tv some channels are better quality that some of the tv channels available in my area
You know your youtube lad. Add Louis Rossmanns everyday life hacks and you are set
Mark Jordan the signal path and eevblog could learn a thing or two from ben krasnow of 'Applied Science'. that guy is a true engineer -- he can actually put his knowledge to use. eevblog and the signal path is basically just unboxings and teardowns of different equipment. cool, you can take things apart... but can you build anything? dave's uCurrent thing was embarrassingly simple for a veteran electrical engineer. if you haven't watched Applied Science yet, please do. that guy does truly amazing things in his garage, and he's very sincere and soft spoken, unlike dave who rattles off a bunch of 'catchphrases' and drives everybody crazy with his annoying upward inflection and throat phlegm.
Americium is mostly an alpha source that tube is only really sensitive to gamma due to the metal can construction a nice project though.
This is a good thing to have if you live near Fukishima, or the Pacific Northwest.
friendofCHAKA yeh , if you live within 50 miles of the reactor , beyond that you can hardly detect any change from the plant.
What about the water near the reactor isn't that toxic and leaking into the Pacific?
As far as i understand it a small amount of material leaked into the Pacific but so little that its hardly worth mentioning. Keep in mind i am no expert , but all the things you read about radioactive seaweed and contaminated beaches in the US are total bullshit. Modern reactors like this one are very safe and have both inner and outer containment. The explosion you have seen on the news was only the outer containment getting blown off by a hydrogen oxygen explosion. This is not a dodgy 80s Russian reactor we are taking about that had no containment at all save for the reactor shielding
friendofCHAKA You are vastly overestimating the amount of contamination and vastly underestimating how huge the ocean is. Any contaminated water is so diluted that the change is practically undetectable by the time it reaches the US.
I suppose more people will probably die from Heart disease from eating McDonalds than Fukishima. Right? haha
shodtech Действительно очень серьезная работа над энергопотреблением и миниатюризацией. И разработка платы в Altium- признак мастерства. Замечательный девайс!
А насчет kickstarter - это очень перспективно, и есть люди, через которых можно запустить проект из наших стран бывшего СССР.
@EEVblog
Americium is an alpha emitter. The muller tube thats in there isn't able to pick up alpha radiation unfortunately so you can't test your souce. Muller pancake style tubes with mica windows are what you want if you want to detect alpha.
Cheers.
Great little design. Are there any decent solid state GM tube replacements? CMOS imager with a scintillating crystal?
you can use google translate with the cam on your smart phone to do instant translations on the fly
I must build one.
I like the coin. Very cool looking. :)
Cool project, i would buy one.
Nice bright display.
@Dave: Apparently there's two http's in the "Russian SBM-10 Geiger Muller tube:" link.
I love the fact that there is a 1.6 Ohm BEARD in that schematic :D
Eh isn't the "window" at the front og the geiger tube? So placing it on top of the radiation source will give a smaller reading than pointing the end at it.
But love the design and video.
Another small detector is the K8 Nuke SafeGuard that only has three small LEDs and goes beep. And powered by a CR2032 button battery. May come in handy if some Middle East country violates its agreement. Have you been to the Uranium mines ? Do you have any Thorium deposits for building safe reactors for the third world countries ? Thank you for a great video that is much needed ! Only seventy (70) years since Trinity Test (16 July 1945 05:29:45 AM).
Eyes UP and lights down, tjl Sent by Win7Pro64 w/ADSL
а откуда схему брали? Не с сайта случайно "радио кот"? Так для справки дозиметр "микрон-1"
а спс, посмотрю
How much is it assembled and tested?
The display is going in the correct direction!!111
Could use a wrist strap or hole for a lanyard or something... just wear the thing so you don't drop it/lose it. Very cool though
What a cool little gadget! I want one!
It looks like it's measuring right in the noise
0:09 - Dave, you gotta admit, Australian ¢50 is a huge freakin coin!
a real work of art...
Some body don't know what drawing program was used to make that schematic thx
cool tech! nice review.
Why generate 400V?
Roy Zalis because that's what the tube needs to do it's job
You should have taken a drive down to Lucas Heights. :) I wonder if they still do tours there?
too bad the files have been removed from github... 😕
You can find a version of this instrument here: www.radiokot.ru/circuit/digital/measure/117/
can we purchase these? it would be fun to have around
***** is there an english tutorial on building one of them then? it just seems like a neat project.
I want one! where can i get one of these
Awesome little piece of tech, should translate to english though!
darcksage1 I wish I knew Russian. Checked out the sources and they look soooo neat and tidy. The bloke is a real perfectionist.
Github repository not available, anybody has saved english source files?
Put this on your key flob, youre golden
You have a weird saying "Too easy" - what does it mean? That the schematic is easy to read/understand or that the parts are easy to connect or ...
Just found your channel - Excellent videos! Thanks
It have buttons from calculator?
Catch you next time!
Does anyone know if there is a kit version of this already? It,s an amasing devise and project. Would realy like to have one. With fukushima going on. I am very worried. Greetz marco
the link to the Russian site is broken.
Andrey, add uSv/h and CPM. Then, *Kickstarter it!*
12 months battery life? I'd be interested to know how they managed that.
orazdow on off on off on off on off ( I guess )
I would have gone with the 20-cent coin because....... platypus!
how useful is ti since i assume its not that accurate...
ShinTsu it's a counter, it cannot be inaccurate.
MrTridac o i assumed that depending on the tube size you are able to read radiation better or worse but apparently that's not the case?
+ShinTsu I wouldn't say good or bad. Sure, if the radiation is very low, the chance that the little tube is hit by a gamma "particle" is also very small. But it's all about probability, so you just count for a little longer (maybe a minute instead of seconds) and calculate the radiation level from there.
"LCD display" is that like ATM machine?? :P
nice vid owise :)
Thing of beauty !
Sorry, but no.
You can't just convert Röntgen into Sievert, they are not the same thing. The former is used to measure ionization (it is a legacy unit though) while the latter describes energy deposited (while taking the different biological effects of the different kinds or radiation into account).
If any dosimeter ever displays any Sieverts to you, there will be a particular assumption built into the logic of the device. You can never be sure if the reading is correct. (Not without additional methods of measurement anyway.)
This is going straight in the PipBoy
I'm sure there's something hot in SW2
EEVblog you still have that online geiger counter? maybe put both into the same place and measure for a day and compare if both more or less agree on the value. I have had bad experiences with these tiny tubes to not be sensitive enough for serious use.
Hi mate.
That is a very nice little dosimeter, well done Trot skies. Strange that the display is in English, but the software is in Russian. Unfortunately, it has been overtaken by the Chinese. Yesterday I was at Jay-car, a local electronics store, and they are selling a sort of dongle, that can be put into an IPhone. The thing was as big as 3-4 match stick held together. Grant you, not a stand alone unit, but much smaller never the less.
Marcel.
Maybe correct translation
catch you next time = увидимся (увидимся в следующий раз)
uuuugh someone needs to sell these.
what a nice gadget!
hi Dave. to translate, you can use google applications. Translates the text from the image
Seems this project have been abandoned. The link to the creator's web page does not work and there are no commitments to the project since 2015. Shame... It was a nice gadget while it lasted.
Sure makes you wonder how the astronauts managed to safely pass through the concentrated radiation of the van allen belt and the general cosmic radiation on the trip to and from the moon and the suface radiation on the moon.
Gromitdog1 actually no. even thought the radiation is higher than on earth its still quite low. the dose they got is only like a few times (apollo 17 9mSv) the anual dose (2mSv) we get from backround radiation. Its not that the van allen belt is a death zone. its just a myth. with only 3mm of aluminum the PEAK rate is 200 mSv/h. with the speed they traveled they passed the belt within a few mins.
наверно самое далекое путешествие ультрамикрона
путешествие в Австралию))
+Электроника
Privet z Italy !!!
Can you send the device to spb?
Sieverts. Ugh.
Did you know that it is a computed value based partly on the tissues involved and the source [x-ray, gamma, neutrons...] of the radiation?
A radiation dose that scored 1 sievert for bones might score over 100 for the eyes or brain. Some tissues are far more sensitive than others, and so get higher sievert scores.
I get the way the unit is used as a composite biological equivalent, but I just felt like being that guy.
I guess it is pondered for an average whole body exposure of radiation. People do not usually get a focalised beam of radiation to one specific part of the body. Unless there are undergoing single beam stereotactic radiation therapy.
Dave, bananas are mildly radioactive, how about measuring their radiation next?(use a bunch of them)
the second link returned a 404 error :(
You can ask me, I understand Russian
Funny fact: Australia is the least radioactive country. The geology of your continent dead for millennia!
DigGil3 Our background is about 1/3 that of the US I believe.
EEVblog Depends on the location of course. It's funny because one of AU's chief exports is uranium. Though as an alpha emitter with a fairly tame decay chain, it doesn't contribute that much. Main problem from it may tend to be radon buildup, which can be an issue in certain AU homes. Still, "traveling by motor vehicle" usually comes in at regularly higher risk than most of this stuff.
Gravity Uranium originates by outcrop from deep under the crust isn't it? That would indicate former ancient volcanic hotspots in Australia, right?.
DigGil3 there's heaps of radiation from the sun out here
Yve Gotnone Cosmic radiation is filtered by the magnetosphere.
Just what I need for my next trip to Chernobyl
well he really should add a jack for headphones so you can be like real radiometrist :)
this is a nice gadget
Hope u tested those Russian cookies for radioactivity before eating them lol.
EEVblog Dave, if you have an iPad, download WordLens. It's far from perfect but it will give you a clue with Russian!
Steve Brace the new google translate app does the same thing... I doubt Dave uses apple products, since he kinda knows his technology xD
therealpanse Not a single Apple product pollutes my life
EEVblog I knew it. xD
therealpanse Well I mean of course. Would you really take an electrical engineer and give him electrical products that basically say "you can do nothing yourself, you must have our proprietary everything, give yourself to the Apple Store cult fully"? He'd probably rather build his own smartphone.
EEVblog What's so different about Apple from other companies? I bet you have a well defined reason :P
EEVblog it's cool and all but I don't know what the size of a Australian 50 Cent coin is ;P.
Adam Jeffords freakin huge, google it )
At the work I had some years go the dosimeters were much more smaller than this (~50 euro cent size) - so it cannot be the smallest dosimeter
now this would be a great wrist watch... fallout "Pip Boy" anyone?
Perfect for when the nukes fall, assuming one survives of course... :P
Not for sale? shame :(
+Sjoerd van Gestel A common view in Russia.I made for themselves, as a hobby. Production is not planned, because selling is bad, unworthy of the engineer.
If you only knew how many ingenious designs vanished in boxes of these masters and remained unknown to anyone except the author and his friends.
I would definitely have run that software on a junk machine...
I want this! :D
Where is schematic and .hex?
I looked at github but only found FW in thousand pieces...
EDIT: lol this sbm-10 sensor costs 22$ :O
***** thanks for info, I found link, try to put myself:
ftp@://www.@радиокружок.n@et/%D0%94%D0%BE%D0%B7%D0%B8%D0%BC%D0%B5%D1%82%D1%80%D1%8B_%D0%9C%D0%B8%D0%BA%D1%80%D0%BE%D0%BD/%D0%A3%D0%BB%D1%8C%D1%82%D1%80%D0%B0-%D0%BC%D0%B8%D0%BA%D1%80%D0%BE%D0%BD/
Remove three "@"
***** Can you convert .schdoc(schematic) to image and add to this FTP?
Because I'm not using altium and cant open file...
***** THANKS!
Do you know where I can buy this sbm-10 sensor cheaper than 22$(with shipping)?
***** Really love it thank you a lot
***** What is final cost(inc. ship.) of this dosimeter?
I need one.
today author released new firmware that allows logging more than month