Mv Measurement; Temperature Measurement; Conductivity Calibration; Setting The Standard Buffer - OHAUS ST400 Instruction Manual

ST400 & ST400M Portable Meter
Press to start the pH measurement, "measuring" appears on the display. Auto or

manual endpoint mode can be used, the pH value with the temperature will display on the
screen with an asterisk on the left.
If the repeatability is poor in the automatic end point mode, or it cannot reach auto end point for a
long time, it is suggested to use the manual end point mode.
Sometimes the repeatability is poor because an ordinary electrode was used to measure special
sample (such as juice, milk, distilled water, tap water etc.) It is recommended to use special pH
electrode, such as ST230 turbidity sample electrode, pure water electrode. For application and
selection of pH electrode, please consult the relevant personnel or technical support.
The pH value of tap water is not the same everywhere, and tap water is usually a low ionic system.
Typically, the pH electrode needs a long time to reach the end-point, and the repeatability is poor.
It cannot be used to judge the quality of ordinary electrodes or meters.
3.5.2

mV measurement

Press▲▼ button to switch between pH and mV measurement.

Follow the same procedure as for pH measurement to perform a mV measurement.

For the ORP (redox potential), it is necessary to connect with the ORP electrode (such as
STORP1) to measure the corresponding mV value.
3.5.3

Temperature measurement

For better accuracy, we recommend to use either a built-in or a separate temperature (STTEMP30)
electrode.
If a temperature electrode is used, the sample temperature is displayed.

If the meter does not detect a temperature electrode, the meter will display "---", It is

necessary to set up the Temperature compensation as MTC and input the temperature.
Note: Meter is compatible with NTC 30 kΩ temperature sensor.
3.6

Conductivity calibration*

This chapter only applies to ST400M.
Before using the conductivity electrode for the first measurement, calibration must be done first.
After the electrode is calibrated, it does not need to be calibrated for a long time. User should
select the standard buffer solution that is closest to the conductivity value of the sample to do the
calibration otherwise it will cause some error.
3.6.1

Setting the standard buffer

Long press (more than 3 seconds)
button to select conductivity settings. press
button and ▼ button to enter conductivity standard buffer settings, press▲ button and ▼ button
button to enter the setup mode, press▲ button and ▼
button to enter conductivity settings, press▲
EN-15