Extech CO250 Portable Indoor Air Quality CO2 Meter with Datalogger - Carbon Dioxide, Temperature, Humidity, Dew Point, Wet Bulb, NDIR Sensor, 99 Record Storage, Large LCD Display

I was looking at the Testo 315-3 but was put off by the price as I won't be using it often. So I decided to go for this Extech for a third of the price, and have been very happy with it's performance. I actually borrowed a friend's Testo 315-3 and compared the two devices side by side (see photo). The Extech is just as accurate as the Testo (tested up to around 1000 ppm). The Testo is slightly faster to react on increasing CO2 levels (by 5-10 seconds), but the same reaction time to decreasing CO2. Also the Extech has better 1ppm resolution, whereas the Testo has 10ppm resolution. As for long-term accuracy and reliability; time will tell I suppose.The Extech has a RS-232 serial cable for data output which was another deciding factor for me. Each second it outputs live readings of CO2, dry-bulb temperature, relative humidity, dew-point temperature, and wet-bulb temperature over it's serial connection. The software that came with it is the typical old and clunky software, but I've since written my own Java library for data monitoring (you can find it on GitHub). I found that a cheap RS-232 to USB converter worked fine as my laptop doesn't have a DB-9 serial port.As others have mentioned it doesn't include a power supply. I bought one locally for cheap. You'll need a 9VDC, 1A supply. I found that a 4.0x1.7mm power jack fit well (centre-positive). Also, the device looks like a CB radio or ancient Nokia phone!! Not the sexiest looking device, but that matters little for my work.I'm happy to recommend this to others.

Just received my device today. Here are some observations:1. The unit comes with a cable that lets you connect it to a computer so you could send and analyze data. However, it is an RS232 cable that needs to be connected to a computer's serial port. Most laptops do not come with serial ports, so you will either have to go out and buy an additional adapter that could be plugged into your laptop's USB port, or you will have to borrow grandpa's old desktop computer to plug it in.2. The software on the CD that comes with the unit only works on Windows XP. I discussed this with Extech technical support and they are "working on an upgrade". Microsoft just recently stopped supporting Windows XP. New computers all come with Windows 8. A lot of people are still running Windows 7. So unless you have an old computer running Windows XP, or you have the technical ability to set up a virtual environment running Windows XP on your newer laptop, the included software will do you no good.3. It has an AC adapter on the side so you could connect a power source. However, for a price of $400, it does not come with one and you cannot order one from them. If you call Extech technical support, they will send you an email with the specifications. You then either have to go somewhere like Radio Shack or order one online.The reason for the two stars is that $400 is a lot to pay for a device that requires you to buy additional accessories like a power supply and a USB adapter. The fact that the software only works on Windows XP basically renders that functionality useless. That's kind of like sending out an instruction video, but then having it only work if you have a VCR or Betamax. All this device seems to do in its shipped condition is to provide you current readings. You cannot do any analysis without the software or cable adapter. You could get the same results for less than half the price with other products.The device itself appears to be accurate and sturdy. Extech technical support was easy to contact and the person was responsive.

Make sure you're happy only using battery power..This seems like a perfect compromise between budget and the Extech SD-800, because this one can log info if connected to a computer --ie. the essential features of the SD-800 if a computer can be used nearby..However, this Extech CO250 does not come with a power supply for the 9VDC socket. Some Extech CO250s do come with an external power unit.Extech does not sell a separate power unit. Also, Extech Technical service states that they don't have any information about the power unit requirements, so they cannot recommend an alternate power source without potentially voiding the warranty. Using any power unit not included with the meter will void the warranty and potentially damage the meter.

Es tal cual el equipo que se anuncia, excelente precio, es muy preciso y muy amigable en su operación lo recomiendo ampliamente

This isn't accurate but for the price point I guess I should have expected that.

Excellent equipment

Very good

Does it do the job it's advertised to do? Yes. It appears to be fairly accurate and works as it should. Is it worth $365? Absolutely not. The side-light LEDs are a joke, the menus are horrible, and it is quite clearly the same as "clone" items costing 1/3 the price.It does not come with a power brick, and the serial cable is a hand-made clamshell thing that looks like it was made by an IT nerd in his basement circa 1995.