General Tools EP8709 Calibratable Multi-Function Digital Psychrometer, Wet Bulb Capable

Dead on accurate, pretty good on batteries, helps alot with HVAC service. Need to get wet bulb? This is a reasonably priced, very accurate gadget that will do just that. I rough house this thing around in the pocket of a tool bag, getting bumped and scraped all day. It doesn't show any signs of the abuse it gets. It just keeps on working. There is no Bluetooth or anything like that, to input into your phone. Just a plain tool. It does its job, and does it well.

Product works well, and is easy to use. perfect fit for me, homeowner, not sure if it would work for a pro...seems to take some time to provide a stable reading. and, pro may break depending on roughness with tools.

I bought a General EP8703 because I wanted an inexpensive calibratable psychrometer. When I saw a used, but like-new, one for under $13 from a third-party Amazon seller, I couldn't resist. Unfortunately I didn't notice the EP8703 doesn't show wet-bulb temperatures, which is a measurement I need, until after I placed my order. It turns out you have to buy the more expensive EP8709 to be able to measure wet-bulb temperatures. I think it's a bit disingenuous to represent an instrument that isn't capable of measuring wet-bulb temperatures as a "psychrometer," but fortunately the EP8703 is easily upgradable to be wet-bulb temperature capable (more on that below).The unit I received was indeed in like-new physical condition but was so badly out of calibration that it would only read 0.0% RH. Since the unit is calibratable, I had no problem calibrating it to read within its accuracy specifications.I did disassemble the unit to examine it before I determined the issue with it was simply a bad calibration. I was pleased to discover that the EP8703 and EP8709 appear to use the same PCB. As far as I can tell, the only difference between the units is the HOLD, WBT, and MAX/MIN buttons have been replaced with a blank plastic plug on the EP8703. Otherwise the case, sensors, PCB, LCD, and firmware are all identical.All I had to do to essentially upgrade my EP8703 to an EP8709 was add the missing buttons. Some tactile switches I had on hand worked great for this purpose. General deserves kudos for making upgrading easy by not crippling the EP8703's firmware.The photo I included shows the upgraded unit and how well its wet-bulb temperature measurement agrees with a direct measurement taken with an accurate thermometer outfitted with a wet sock and placed in front of a fan. This is the most accurate digital psychrometer I own.The build quality is decent for an inexpensive instrument, but I wouldn't expect it to hold up nearly as well as a unit costing several times as much for long-term field use. The rubber overmolding feels good in the hand, and the case's torsional rigidity is much better than I expected. The unit doesn't seem particularly rugged, but it should be sufficient for light field use or occasional DIY work.Overall, I like this unit for the price I paid.

Got this. Wasn’t happy that the temp was in small numbers and the humidity was in big numbers. The display seemed washed out and hard to read.. was sent back

It takes a while to get an accurate reading. But it does a good job after that.

I have a brand new unit & it always reads the humidity 5-10% lower than the expected humidities of saturated salt solutions (outside the stated 3% accuracy range). I have repeated my tests on several occasions with different salt solutions & got the same lower than expected results. So they are not just random fluctuations. It appears that the factory calibration is off. I will be returning it to Amazon.

Does the job, seems to work well

I have now had time to use this professionally and it has been very accurate.

Our technicians love them. Good readings and accurate. Nice and compact. Only thing that is that it should come with a carrying case.Rob