Printable Version

To ensure success in selecting the right Conductivity/Resistivity sensors for a particular application, users should first consider the following questions and guidelines:

    1)  What are the minimum and maximum Conductivity/Resistivity values of the solution?
           • Choose a sensor whose range completely encompasses the application range; the application range should
              fall within the middle of the sensor's operating range.
                       Example:  If an application has a conductivity range of 500µS to 1000µS, the best sensor choices
                                          would be the 3-2821 or 2841 not the 3-2820 or 3-2840; this is because 500µS to 1000µS
                                          is closer to the middle of the 3-2821 sensor's range (10µS to 10,000µS), compared to the
                                          3-2820 sensor's range (1µS to 1,000µS).
          • GF Signet manufactures sensors that have specific cell constants to match the water quality:
            (.01, 0.1, 1.0, 10 and 20)

    2)  What are the minimum and maximum temperature values of the solution?
          • Knowing the temperature range can determine the compatible fitting material required.
          • Signet can upgrade the sensor fittings with either stainless steel or titanium depending on the temperature
             requirements. Standard Signet conductivity sensor fittings are made of either polypropylene (PP) or PEEK™.
.

    3)  Are the chemicals in the solution compatible with the wetted materials of the sensor?
           • Look up each chemical and wetted material in a reliable chemical compatibility chart, or contact your Georg Fischer Technical Support staff for assistance.
          • Monel and Titanium sensor bodies are available as replacements to the standard stainless steel sensors.

    4)  What is the distance between the sensor and the location of the transmitters?
          • All Signet Conductivity sensors have cable length restrictions (See Figure 1 below)
          • If extended cables are necessary, they can be special-ordered directly from GF Signet. A solid uninterrupted
            cable will improve the signal quality and contribute to better performance (preferred over soldered extensions).
          • If the cable must be extended in the field, Signet recommends the 3-8050-1 universal junction box in
            conjunction with proper Signet cables (listed in the catalog)
          • NEVER exceed the maximum specified cable length. Excess cable will cause errors in the measurement.

 

Figure 1:  Cable Lengths
Sensor	Description	Standard Cable Length	Maximum Cable Length
3-2819-X	0.01 cell, SS body, PP fitting	15 ft / 4.6 meter	25 ft / 7.62 meter
3-2839-X	0.01 cell, SS body, PEEK fitting	15 ft / 4.6 meter	25 ft / 7.62 meter
3-2820-X	0.1 cell, SS body, PP fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2840-X	0.1 cell, SS body, PEEK fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2821-X	1.0 cell, SS body, PP fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2841-X	1.0 cell, SS body, PEEK fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2822-X	10 cell, SS & CPVC body, SS fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2842-X	10 cell, SS body, PEEK fitting	15 ft / 4.6 meter	100 ft / 30 meter
3-2823-X	20 cell, SS body, SS fitting	15 ft / 4.6 meter	100 ft / 30 meter

    5)  Are there any recommended sensor installation tips?
          • See the Figure 2 below.

Figure 2:   Sensor Insertion Position in the Pipe
Figure 2a	This installation shows the proper method of installing a sensor in a high purity water application. Note that the holes in the sensor body are installed so they allow trapped air to flush out of the sensor's electrodes.
Figure 2b	This installation is also suitable for low GF Signet conductivity sensors measuring low conductivity solutions.
Figure 2c	These installations are suitable for sensors with a cell constant of 10 or 20. It is not recommended to install a low conductivity cell into a flow stream using the Figure 2c and 2d configurations.
Figure 2d