How to make an ice point test

Ice Point Introduction

The Ice point check offers a swift and convenient method to verify the precision of your temperature measuring instruments, ensuring an accuracy of ±0.01ºC at 0.00ºC or ±0.018ºF at 32ºF. Moreover, this test serves as an effective means of monitoring potential trends or emerging issues, such as temperature drift, in your temperature measuring instruments.

By adhering to a monthly timetable for conducting ice point checks and maintaining a record of the results, any underlying problems can be readily identified. A comparative analysis between the most recent temperature readings and those from the preceding months enables you to gauge the impact of temperature drift on the accuracy of your temperature measuring device.

It is advisable to accumulate test results from a minimum of three to four months before definitively confirming whether temperature drift is compromising the accuracy of your temperature measuring device.

Test Items Required

  • - A 3kg bag of ice.
  • - One bucket approximately 255mm (10 inches) high for holding the ice mixture during testing.
  • - An ice shaving machine or similar utensil capable of producing 1mm-sized ice pieces.
  • - A one meter (three and a half foot) long plastic tube; a 6mm (1/4 inch) o/d tube is suitable. Used to siphon excess water from the bucket.
  • - A metal or plastic rod approximately 3mm in diameter and 200 to 300mm long, used for making holes in the ice during the setup phase of the test.

Setup Process

1. Preparation: Fill the shaved ice bucket with one-third cold water.

2. Shaving Ice: Meticulously shave the ice using the ice shaver to produce finely crushed pieces, ensuring a maximum size of 1 mm (about 0.04 inches).

3. Setup: Position the siphon tube inside the bucket, securely resting it on one side with one end placed at the bottom of the bucket and the other outside the bucket.

4. Ice Packing: Pack the shaved ice into the bucket tightly, creating a compact arrangement that supports the siphon tube at its designated position.

5. Compression: Continue adding shaved ice and applying pressure until the bucket is filled to the brim with tightly packed ice, ensuring ideal conditions for testing.

6. Water Removal: During the test use the flexible hose to siphon all accumulated ice melt water from the bucket.

7. Temperature Stabilization: Allow the ice point setup to stand for 15 minutes to reach a constant temperature from top to bottom before testing. Optionally, place towels over the ice point to act as an insulator and help slow down the rate of ice melt.

8. Thermometer Probe Placement: Using the metal or plastic rod, create a hole partway down the middle of the ice, ensuring it matches the depth of the probe, maintaining a distance of at least 50mm (2 inches) from the bottom of the bucket. Insert the thermometer probe into the hole, firmly packing the surrounding ice to ensure uniform contact

9. Sampling Preparation: Before sampling, allow the temperature probe to equilibrate with the internal temperature of the ice point setup, typically five minutes is sufficient. Check the thermometer display to see when the temperature settles around 0.01 degrees Celsius (32.018 F). 

10. Recording Data: To ensure systematic recording of data first you will need a worksheet to record your data to, begin by adding the date of the test and the serial number of the thermometer under examination to the worksheet. Throughout the testing process, meticulously log the time each sample was taken plus the corresponding thermometer reading, do this on separate rows down the worksheet. Maintain a consistent interval of one minute between samples. Aim to gather at least eleven samples during the test. (number of samples - 1).

11. Analysis: For the thermometer under test you can compare data from previous ice point tests with the latest ice point test readings to evaluate how a thermometer is behaving i.e. is it still displaying accurate temperature data when compared to the last ice point test.

Temperature Errors and Mitigation

Stem Effect: Stem effect occurs when a temperature probe is not adequately immersed in the temperature of interest, leading to inaccuracies in readings. To avoid stem effect errors, insert the probe to a depth at least ten times the diameter of the temperature probe.

Additional Steps for Accuracy

  • - Insert the probe deeper into the ice, maintaining a minimum distance of 50mm (2 inches) from the bottom of the ice bucket.
  • - If the ice develops a frosty layer during testing, pour a little cold water over it until the appearance of the ice turns clear again, compress the ice as required.
  • - Replenish the ice as necessary to maintain the original height and shape of the ice point.
  • - Check for water presence in the bucket, which can cause higher-than-expected temperature readings; remove the excess water using the siphon tube to help improve accuracy.

Now it's time to give it a go and set up your own ice point test. By following the steps outlined above you will be well placed to build your own ice point tests that give you confidence in the reliable results produced. 

 If you would like to receive a free pdf copy of the ice point test form, use the link below. 

Enter your name and email below then click on the Worksheet button.

Posted: Wednesday 14 February 2024

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