The conductivity meter is a laboratory conductivity measuring instrument, which can not only measure the conductivity of ordinary liquids, but also meet the needs of measuring the conductivity of high-purity water. The instrument has a signal output of ~1mV, which can be connected with an automatic electronic potentiometer for continuous recording. Measurement principle: In electrolyte solution, charged ions move under the influence of electric field to transfer electrons, so they have conductive effect. The strength of its conductivity is called conductance S. Because conductance is the reciprocal of resistance, two electrodes can be inserted into the solution to measure the resistance R between the two electrodes. According to ohm's law, when the temperature is constant, this resistance is directly proportional to the electrode spacing L(cm) and inversely proportional to the electrode cross-sectional area A(cm). That is:
(1) For an electrode, the electrode area A and the distance L are both fixed, so it is a constant, which is called the electrode constant and expressed by Q, so the formula (1) can be written as:
(2) In the formula, the electrical conductivity is expressed by K, and its unit is known by the formula (1). Therefore, equation (2) becomes.
(3) because this unit is too large in engineering, it is used as a unit, called or.
in formula (4): rx-liquid resistance RM-voltage dividing resistance.
it can be seen from formula (4) that when e, Rm and q are constant, the change of k will inevitably lead to the corresponding change of Em. Therefore, by measuring the size of Em, the liquid conductivity can be measured. The telecommunication components of the instrument are all installed on the panel, and the circuit components are centrally installed on a printed board, which is fixed on the opposite side of the panel. K: high-cycle and low-cycle switch; : electrode constant regulator; : calibration and measurement switch; : Calibration regulator; : Range selection switch; : Capacitance compensation regulator. Kx:: electrode socket; : 1mV output socket. K: power switch; XE: neon lamp.