The HD 9212 is a combined instrument for measuring pH, mV and °C. The instrument is provided with a EURO S7 CAP connector for pH electrodes, electrodes for measuring redox potential (ORP) or specific ion electrodes (ISE). All the electrodes available on the market may be used on condition that the instrument have a connector directly on the EURO S7 electrode. The TP 9A temperature measuring probe is connected to the instrument by means of a 8-pole DIN connector. During pH measurements this probe is used to set the compensation temperature. The temperature coefficient is compensated manually. A mechanical push-button panel protected by a polycarbonate membrane allows to select the desired unit (pH, mV or °C). The adjustment of the asymmetry and of the slope in pH measurements is carried out on the push-button panel. The calibration data stay memorized even when the instrument is turned off. To turn the instrument on or off, press the ON /OFF button. The instrument will also turn itself off automatically after about 8 minutes if it is in the measuring mode. Automatic cut-off in the measuring mode may be avoided by pressing ON /OFF + °C/°F while switching on.