We are offering portable ph meter, temperature meter, mv meter etc. the meter are used to measure acidity and alkalinity of liquids. microprocessor-based:sts-321 has built-in high performance cpu, it can work about 200 hours continuously with 9 volt battery. two points push-button calibration:the meter with two points calibration function, it will prompt ph calibration solution when you calibrate the meter, you need only immerse the ph electrode into standard solution and press enter key, then the meter will be calibrated automatically. auto-buffer recognition:in calibration, the meter will display error if you use ph standard solution by mistake or not by the calibration prompt. Viewing of electrode slope:after calibration, the meter will indicate electrode slope, you can judge by the indicator to replace electrode or not. automatic temperature compensation:sts-3 series with temperature sensor, you can view temperature value on the lcd, the meter with automatic temperature compensation for accurate reading under changing conditions. hold function:the meter with hold function, press meashold key, the meter momentarily freezes reading. Message indicator:sts-3 series with operational message indicator. When you need setup or measurement, the message indicator will help you what you can do and how do it. You can set parameter or select functions under it's guide. Save data:the meter can save 50 data sets, press save key, and the meter will store current measured value, serial number, date, time and other information. Output data:the data can be sent to computer through usb communication interface, you can print out test report via software. model sts-321ph range -2.0016.00phph accuracy 0.01phmv range 01999mvmv accuracy 1mvorp range 01999mvorp accuracy 2mvtemperature range 0100.0 or 32212oftemperature accuracy 1.0, 1.8oftemperature compensation 0100.0, 32212ofcalibration points 2 pointsph standard solutions nist, ph4.006.869.18 or usa, ph4.017.0010.01memory 50output usbpower requirement 9v800ma batterydisplay 4.3 inch lcddimension 185(l)mm88(w)mm32(h)mmweight 300g