Digital Thermohygrometer A compact electronic device for measuring temperature and humidity in the laboratory or growroom, with a large, easy-to-read LCD digital display. While not as accurate as larger, more expensive analog or digital thermohygrometers, we recommend the H0122 and use it in our own growrooms. Can be hand-held for spot checking of particular sites or set in a fixed location with the included wall mount. Measures 32–122 F (0–50 C) and 25–95% rH. Temperature accuracy of ±2° F from 32–104° F (±1° C from 0–40° C), humidity accuracy of ±5% rH from 59-104° F (15–48° C. Includes "Max-Min" controls for recording maximum and minimum levels for both temperature and humidity. Requires 2 AAA batteries (not included). H0122 $54.95

Polythermal Professional Hygrometer This hygrometer is quality crafted and guaranteed to be accurate to three percent rH upon shipment. A newly developed synthetic element gives this hygrometer far better response and accuracy over time than the old style spring or paper hygrometers. Accuracy of ±3% rH. Flange allows for easy wall mounting. H7000 $139.00

Digital Psychrometer This unit is an excellent compromise between less accurate, "consumer" grade digital thermohygrometers and highly accurate but complicated analog sling psychrometers. Measures humidity from 0 to 100% rH, with accuracy of ±4%. Measures temperature from -4 to 122° F (-20 to 50° C) with accuracy of ±1.8° F (±1° C). Resolution is 1° F, 1° C, and 1% rH. Data functions include Temperature, Humidity, Dew Point and Wet Bulb Temperatures, "Min/Max" and Data Hold settings. Requires 2 AAA batteries (included). DPS100 $99.95

Sling Psychrometer A practical, high quality sling psychrometer. This psychrometer, like others, uses a wet bulb and dry bulb thermometer for determining exact relative humidity and dew point. However, this one is superiorly designed for the protective case into which the thermometer inserts when not in use. Sling psychrometers are essential for calibrating hygrometers (please note that all hygrometers should be checked periodically for accuracy). Highly recommended for the professional cultivator. SP7011 $99.95

The HC201 Duct Humidistat This is an economical device for controlling rH, with a 10–94% range with a 3–5% humidity differential. Dial in the desired humidity and the HC201 activates humidifiers to maintain the selected moisture level. (Note: this unit should be mounted with the sensor unit in your air system's recirculation duct in order to achieve maximum accuracy.) The HC201 becomes increasingly accurate at higher humidity. Rated at 7.2 amps. Ready to wire, with simple instructions included. Works with either 115 or 230V current. Should be used in conjunction with the Humidistat Relay (below) when used to operate devices with a startup amperage of more than 43.2 amps. For use in grow rooms and similar environments; not suitable for use in atmospheric sterilization chambers or other environments exceeding approximately 100° F. HC201 $169.00

The HC2000 Professional Humidistat This is a heavy-duty, highly accurate device for controlling humidity in the growing environment. Because this unit keys off of relative humidity (rH), the HC2000 requires a more intensive initial setup than the HC201; the unit must be initially calibrated to precise ambient humidity using a highly accurate tool such as our SP7011 Sling Psychrometer (above). Once calibrated, the HC2000 provides superior control over humidity with an incredible accuracy of ± 1%, in optimal operating range of 20-95% rH. Unlike the HC201 which must be situated in an air duct for maximum accuracy, the HC2000 can be placed nearly anywhere in the grow room. Encased in a durable metal housing, these units have been known to operate for over 20 years in extreme conditions without failing! Comes ready to wire with built-in wall-mountable junction box. Rated at 10 amps. Should be used in conjunction with the Humidistat Relay (below) when used to operate devices with a startup amperage of more than 50.4 amps. HC2000 $329.00  Replacement humidity sensor HC2000-1 $49.95

Humidistat Relay When utilizing a humidistat with devices that have a greater startup amperage than that of the humidistat, it is necessary to install a relay between the humidistat and the device being controlled. Includes a watertight enclosure. (Note: this device must be installed by an electrician to local codes!) HCR100 $79.95  HCR100E for 230V/50Hz applications $89.95