Conductivity Probe

Basis of Operation

• A constant voltage (AC) is imposed across a 1 cm gap between two electrodes. The magnitude of the resulting current is determined by the ability of the solution to conduct the current, where conductance is the reciprocal of resistance. Conductance is report with units of microsiemens (mS). Conductivity is reported with units of mS/cm.

Auto ID Capable?

• Yes

Calibration

• A standard calibration is loaded with Logger Pro, but for more accurate work you should calibrate the conductivity probe before use. Use the following instructions to perform a two point calibration:
  • From Logger Pro select Experiment:Calibrate:Pick Sensor.
  • Select the appropriate conductivity range setting on the probe box (low = 0 to 200 mS, medium = 0 to 2000 mS, high = 0 to 20,000 mS). Note - you need to determine which range is appropriate for your work.
  • From Logger Pro select Experiment:Calibrate:Pick Sensor.
  • Click on Calibrate Now.
  • With the probe in the air, collect the zero point calibration.
  • Place the probe in a solution of known conductivity and enter the value in the appropriate box. Allow the reading to stabilize and then press Keep. For even better results, repeat with a second calibration standard that will bracket the expected conductivities of your samples.
• Recipes for typical conductivity standards are given here:
  • 0.0474 g NaCl in 1.000 L of deionized water has a conductivity of 100 mS/cm
  • 0.491 g NaCl in 1.000 L of deionized water has a conductivity of 1000 mS/cm
  • 1.005 g NaCl in 1.000 L of deionized water has a conductivity of 2000 mS/cm
  • 5.566 g NaCl in 1.000 L of deionized water has a conductivity of 10,000 mS/cm

Preparing Probe for Use

• Rinse and blot dry the tip of the conductivity probe with deionized water.
• Place the tip of the probe into the sample to be tested. Be sure that the elongated cell is completely immersed in the sample and that it is free of air bubbles.
• Gently swirl the probe and wait for the reading to stabilize; this may take several seconds.
• For temperatures below 15 °C or above 30 °C you may need to allow more time for a stable reading.
• The conductivity probe cannot be used at the same time as you are using the pH probe as it will distort the readings of the pH probe.

Maintenance and Storage

• The conductivity probe is stored dry. Rinse it with deionized water and blot dry.
• If the probe is contaminated, soak it in a dilute solution of a mild detergent for 15 minutes, followed by soaking it in 0.1 M HCl for an additional 15 minutes. Rinse well with deionized water and blot dry.

Specifications

• temperature range of 0 to 80 °C
• automatic temperature compensation from 5 to 35 °C (reported value is conductivity as if the solution were at 25 °C)
• precision
  • low range is ±0.1 mS/cm
  • medium range is ±1 mS/cm
  • high range is ±10 mS/cm
• accuracy
  • low range is ±2 mS/cm
  • medium range is ±20 mS/cm
  • high range is ±200 mS/cm
• response time of 5 sec for 98% of full-scale reading and 15 sec for 100% of full-scale reading
• maximum sampling rate is 40 points/sec with typical rate of 1 point/sec

Chemical Tolerance

• Do not place the probe in viscous organic liquids, such as heavy oils, glycerol, or ethylene glycol.
• Do not place the probe in acetone or non-polor solvents, such as pentane or hexane

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