Contact and electromagnetic conductivity sensors

The advantage of electrode type lies in its price, but its "polarization" defect is too obvious. When current passes through the electrode, oxidation or reduction reactions occur, which change the composition of the solution near the electrode and cause a "polarization" phenomenon, resulting in crystal scaling on the electrode surface. If not cleaned in time, it can cause serious errors in conductivity measurement, even damage, and poor service life. Even if high-frequency alternating current measurement method is used, it is only to alleviate the polarization phenomenon mentioned above. To maintain measurement accuracy, it is necessary to clean and calibrate it regularly in a timely manner. Every time the sensor is cleaned or replaced, it must be shut down and cut off, which affects efficiency. So, most foreign devices use non-polar sensors.

The measurement principle of the non-polar sensor adopts a pair of wire wound alloy ring coils, and the probe of the sensor is isolated from the measured process solution (non-contact). Two coils, one as a transmitter and the other as a receiver. When the transmitter coil is energized, the electrolyte solution conducts electricity and generates induced current, which is proportional to the conductivity of the solution. The receiver coil detects the magnitude of this current to determine the conductivity value of the solution. The conductivity probe is customized with two wire wound alloy circular coils in a corrosion-resistant circular mold. Because the probe of the sensor is isolated (non-contact) from the measured process (liquid), there is no need for frequent maintenance and upkeep. Compared to the traditional electrode based conductivity measurement process, it fundamentally avoids ion deposition and coverage on the electrode surface, and issues such as polarization, oil contamination, or pollution will not affect the performance of non-polar sensors. The service life can last up to 10 years.

Electromagnetic conductivity sensors are available for the following choices：

Built in temperature sensing element: PT-100；PT-1000；Thermistor MF5E-2.202F

shellPackaging material: PP；□PFA；□ABS .

range: ：0~2mS/cm；0~20mS/cm；0~200mS/cm；

0~2000mS/cm；定制___mS/cm.

output lineCable:standard length：5rice ；custom length___rice.

signal processor:Built in type; External type.

Resolution:1uS;1mS

Signal output typeAnd working power supply:

Voltage type,output signal: 0~2000mV.

doublepower supplyWorking type: ± 9.5V (Min)~± 12V (Max) DC @ 20mA typ

singlepower supplyLow power type: 5VDC (Min: 4.55VDC~Max: 5.25VDC)

@12mA type.

Current ring (three wire system),output signal: 4 ~ 20mA, * can drive large loads500Oh, yeah.

workpower supply: 21V(Min) ~ 26V(Max) dc @ 45mA typ.

Digital type, three types of communication serial ports:TTL；RS232；RS485

Wide voltage working type: 5.25V (Min)~15.5V (Max) DC

@20mA type.

Low voltage and low power consumption type: 5VDC (Min: 4.55VDC~Max: 5.25VDC)

@15mA type.

Note: For digital communication protocols, see alsoIntroduction to Digital Conductivity Sensors.