BTMETER BT-866A Pro Handheld HVAC Anemometer for CFM Air Flow, Wind Speed Meter Gauge Measures Wind Velocity Temp%RH Dew Point with USB Sync to PC

We wondered why we were seeing mildew in our bathroom. This was the measurement tool to give us the answers. It turns out that our bathroom exhaust fan woefully inadequate for pulling moisture from the shower. The same day that this meter arrived we determined a) the fan was working at the flow rate advertised and b) Amazon would sell us a replacement fan with much higher flow. Problem fixed after one more Amazon package. Note you might have to do a little cardboard, scissors, and duct tape work to match the meter to the vent.

I specifically used this device to measure air flow from the heater vent registers in my home. Readings were very accurate an greatly assisted in determining resister issues. It is excellent that it uploads data to your computer for real-time display and recording. The carrying is also a big plus.

First, the USB connection does NOT power the meter, so if you are going to do long term logging, your battery may die! WHY doesn't the USB power the meter???? What is so difficult to accomplish this?Second, from the videos I have seen and the one that I received, the fan is NOT balanced and has a heavy side. This would affect low air speed measurements!I screwed around with some weights to get the blade somewhat balanced but it is still a little off. Not worth returning because I would just get the same thing.Why is producing a balanced fan so hard????Just shows how cheaply made this is!Also, does NOT do averaging... ONLY min/max/real time.Yet another lie in the description and functionality.Some buttons you hold for 3 second, some for 4... WHY???Pretty poor and sloppy implementation to an otherwise fine instrument... guess you get what you paid for!A hint... check the fan's balance by holding the meter vertical, with no airflow, and see if the fan tries to swing to the heavy side. This will tell you that low speed measurements will probably be wrong.

Changing UNIT and FUNCTION have to be done every time the unit is turned off.The auto off is very short...not enough time to make RH% readings or TEMP. reading .Not user friendly.Would not recommend.Hope this helps.

I wanted to make some psychrometric calculations but was sadly disappointed. Temperature was a few degrees in error but humidity was reading 17% when actual was 44-45%. I have some confidence in the numbers because I laid our three other devices, which were all of difference manufacture but all in agreement and impressively close. Perhaps they were rushing these BT units out the door and forgot to make the calibration. I had no standard for airspeed calibration to compare but after seeing these results I cannot trust any numbers that the BT66 reports.

Good

Great tool

For some reason I forgot it was an anemometer and that the temperature readings and %RH would change instantly moving from outside to inside with no wind (air flow) outside or inside. I put it in my refrigerator, no air flow, so the temperature readings did not change rapidly, they changed slowly. The temperature sensors are inside the tunnels (or "holes") likely to shade them from radiation (like sunlight) to assure that the readings are for the air flowing through the tunnels. The instructions are helpful, making changes quite easy. And, the software/USB worked without any issues. Time now to get to tuning my HVAC system (air-to-air heat pump with three ducted air handlers for three separate zones). Not bad for tuning the home hot yoga studio either as to desired temp and %RH (as measured at output of a fan).