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Calibrate a drop counter

Improve the accuracy of a drop counter, such as the Wireless Drop Counter (PS-3214) or the PASPORT High Accuracy Drop Counter (PS-2117), by calibrating the measurement.

Note

This calibration procedure will require the use of a drop dispenser. Materials for assembling such a device are provided with the Wireless Drop Counter and PASPORT High Accuracy Drop Counter. If you do not have these materials, you can order a separate Drop Dispenser (PS-6935) from PASCO. For instructions on assembling the Drop Dispenser, see the manual for your chosen drop counter or the Drop Dispenser.

Setup

  1. Assemble the Drop Dispenser. Mount the Dispenser to a support rod.
  2. Fill the Drop Dispenser's syringe with titrant. Place a beaker under the Dispenser to catch the titrant as it falls.
  3. Open both stopcock valves, then adjust the valve on the bottom stopcock so the drops fall at a rate of about 1 drop per second. Once this rate is achieved, close the valve on the top stopcock. Discard the titrant in the beaker as directed by your instructor.
  4. Mount the drop counter to the same support rod as the Drop Dispenser, between the Dispenser and the base. Align the Dispenser's drop tip with the drop counter's rectangular window.
  5. Place a 10 mL graduated cylinder under the drop counter window to catch drops from the drop tip. This will give you a measure of titrant volume.

Calibration

  1. Connect the drop counter to Chemvue.
  2. From any page, select a Displayed Measurement button and choose Fluid Volume. This is the only drop counter measurement which can be calibrated.

  3. Select the same Displayed Measurement button again, then select Calibrate.

    Open Calibration Window

  4. In the Calibrate Measurement window, select One Standard (1 point slope) from the dropdown list, then select Next.

    One Standard (1 point slope)

  5. Open the top stopcock valve on the Drop Dispenser, allowing titrant to begin dripping into the graduated cylinder. Chemvue will automatically begin recording the number of drops next to the Sensor Value text.

    Note

    The live Sensor Value measurement is listed as being measured in mL. However, it is actually a measurement of the number of drops.

  6. Once about 5 mL of titrant has been collected in the cylinder, quickly close the top stopcock.

  7. Carefully measure the exact value of titrant in the graduated cylinder. Enter this value, in mL, into the Standard Value box and select Set Current Value to Standard Value.

    Calibrate the drop counter

  8. Review your calibration and select Apply.

    Review calibration