Easy to use temperature data logger - logo


Why running an “ice-slurry” test is not a good solution


If you are doing an ice-slurry test on Clever Logger because it is being used in a vaccine fridge, then STOP!

Strive For Five section 4.4 applies to thermometers. It does not apply to temperature loggers.  Strive For Five makes a clear distinction between temperature loggers and thermometers, and the ice-slurry test is specifically for thermometers.  

The infamous "ice-slurry test"

The ice-slurry test is an often (ab)used test for thermometers and temperature loggers to see how accurate they are.

The two big benefits of the ice-slurry test are:

  • it provides a “reasonably” accurate and predictable temperature of 0°C
  • it holds it for an extended period, giving the device time to settle down to a constant reading
But it is also these assumptions that make it a bad solution.

Problem 1: It isn't 0°C

Many people think they can get some ice, smash it up a bit, pour in some water, and that’s an ice-slurry test.

The problem with this solution is that:

1. water, by definition, is above 0°C and if your thermometer is mainly in water, it is above 0°C.

2. ice, by definition, is below 0°C and if your thermometer is primarily surrounded by ice, it is below 0°C.

You really need shaved ice, in a slushy type environment. To get very accurate, you need pure water and a couple of other factors.

Practically, it is likely that the ice-slurry that you are measuring will be above 0°, and given the next problem, likely to be significantly above 0°C.

Problem 2: Sensors take time to adjust

When you place a device in the ice-slurry, it will take time for the device to drop to the temperature of the slurry. For some devices this could be seconds. For many it is a minute or more. 

The only way you can tell that you have reached a stable temperature is to take a reading, wait at least 15 seconds, and take a second reading. If they are the same then the temperature has stabilised. With thermometers, this is relatively easy.

With a logger, however, this means you need to wait for two consecutive readings to be the same. The only way you can guarantee this is for it to be in the ice slurry for an extended period. 

With Clever Logger, you are limited to a 3 minute sample rate, so it needs to be in the ice-slurry for at least 10 minutes to ensure a stable reading. Keep in mind, however, that as time goes by, the ice-slurry will slowly warm up.

BUT then Strive For Five only applies to thermometers, not loggers!!!

Problem 3: Loggers are electronic

Thermometers are designed to be water proof and generally have a sensor that can easily be placed in water.

Most temperature loggers are not water-proof. They are not designed to be placed in water and ice. You can seal them in a bag and place it in the water, but keep in mind that this will slow down their response times. It will take them longer to settle at the correct temperature.

BUT then Strive For Five only applies to thermometers, not loggers!!!

Problem 4: Wireless signals don't get through water or ice

Clever Logger (and every other wireless device) has the extra challenge that signals can not get through water and ice. 

This doesn’t mean an ice-slurry test is impossible. It just means you can’t watch the results live to see when it settles down. 

BUT then Strive For Five only applies to thermometers, not loggers!!!

Ice-slurry tests are great for thermometers as a quick peace-of-mind test.

They are not intended to be a reliable check for temperature loggers.


You're going to love Clever Logger

To prove it, we’ll send you a Starter Kit to try out for a whole month.

Set it up, have a play, explore the features – obligation free.

If you love it, just let us know.

If not, just send it back.

What is NATA?

The National Association of Testing Authorities (NATA) is the recognised national accreditation authority for analytical laboratories and testing service providers in Australia. It is an independent, not-for-profit organisation that provides independent assurance of technical competence. 

NATA accredits organisations to perform testing and inspection activities for their products and services. This gives consumers the assurance they need to make safe, healthy and reliable choices .

Location Views

In the top right corner of the Location page, you will find the View chooser.

There are three options: Simple, Detailed and Gauge.


Other "How To" articles

Frequently Asked Questions