A pH meter is essentially a high impedance Volt meter, that can measure the potential difference between the internal and external glass surfaces of the pH sensor. A pH meter has an input impedance of at least 1 million Mega ohms.

Environmental or mechanical problems often affect pH measurements. Typically, in these conditions, pH meters give a false pH 7 reading and, since in most applications, pH 7 is the expected value, the user is not aware of the problem.

Examples of a false pH 7 reading:

• the glass bulb of the pH electrode is broken
• loss of signal (up to hundreds of Mega ohms) of the electrode/meter connection cable, due to environmental humidity
• cable or connector short circuit

To prevent erroneous readings due to system failures, HANNA presents HI 83140. Should any of the above listed problems occur, HI 83140 will read pH 4. Since the user is not expecting a similar value, he will be immediately warned about the system performance.

Moreover, the Clean and Cal function helps by avoiding the calibration of a dirty pH electrode, that might introduce a systematic measurement error. Simply immerse the electrode in the HI 50021 Check solution and press the Check button: if the green LED lights up, you're good to go, if the red LED turns on, the probe needs cleaning before being calibrated.

• Range:  pH:  0.00 to 14.00 pH
• Range:  mV:  ±1999 mV
• Range:  Temperature:  0.0 to 100.0°C
• Resolution:  pH:  0.01 pH
• Resolution:  mV:  1 mV
• Resolution:  Temperature:  0.1°C
• Accuracy:  pH:  ±0.01 pH
• Accuracy:  mV:  ±1 mV
• Accuracy:  Temperature:  ±0.4°C
• pH Calibration:  manual, 2 point, through trimmers, (offset ±1 pH; slope 85 to 105%)
• Temperature Compensation:  Automatic, 0 to 70°C (32 to 158°F)
• pH Electrode:  HI 1217-6 with internal temperature sensor, DIN connector and 1 m (3.3') cable (included)
• Input Impedance:  10¹² Ohm
• Battery Type / Life:  1 x 9V / approx. 100 hours of continuous use
• Environment:  0 to 50°C (32 to 122°F); RH max 95%
• Dimensions:  164 x 76 x 45 mm (6.5 x 3.0 x 1.8")
• Weight:  180 g (6.3 oz.)

HI 83140 is supplied with HI 1217-6 pH electrode, pH 4 and pH 7 buffer sachets, HI 700661 cleaning solution (2 x 20 mL sachet), HI 50021 Check solution (2 x 20 mL sachet), calibration screwdriver, battery, protective case and instructions.