The Bluelab Guardian Monitor measures all three critical parameters to successful plant growth - pH, conductivity and temperature. 

A flashing alarm lets you know if one of your parameters moves out of the range you've set so you can make needed adjustments quickly.

Advantages of the Guardian Meter:

Large Plant Safe green LED display with adjustable brightness
Selectable values for conductivity and temperature
Simple push button pH calibration
No calibration required for conductivity and temperature
Silent alarm for BOTH high and low settings
Settings retained when power lost (non-volatile memory)
Automatic temperature compensation
International power supply
Water resistant design

The Bluelab Guardian Monitor saves you time whether you're growing in a greenhouse or an indoor growing chamber. It eliminates the need for test strips or manual meters. When the Guardian Monitor is on duty, you don't have to be!

Specifications:

pH Range = 0.0 – 14.0
EC Range = 0– 50 CF
TDS Range = 0–2500
PPM Range = 0–3500
Temperature Range = 32-122 °F (0-50 °C)

Caution: DO NOT allow the pH probe tip to dry.

2-year warranty (6 months on probe).

More info (PDF format)