A great all around meter for nutrient applications needing constant monitoring. It measures PPM, pH and Temperature. Its large illuminated green LCD display allows easy reading from a distance. Both pH and PPM are temperature compensated for accurate readings. The electrodes are replaceable at a relatively low price. Calibration screws are conveniently located on the front for easy access. The chip is programmed to use the international water standard 500 PPM = 1 EC TDS measurement. It uses a standard 120 volt AC current to low voltage DC power supply. The 24-7 Nutrient Monitor™ comes with 4oz bottles of 1382 PPM, pH 4.0, and pH 7.0 calibration solutions. This meter and PPM electrode has a one year warranty and six month warranty on the pH electrode.