Slushy WizzTemp Test
Verify WizzTemp sensor accuracy against a 0°C ice-water reference — the definitive temperature calibration test for the FizzWizz.
Slushy WizzTemp test
The Health Check (Ident C) confirms the temperature reading is plausible. This test confirms it is accurate by comparing against a 0°C / 32°F ice-water reference — the only way to prove the probe is genuinely calibrated.
The FizzWizz must be in Test Mode before starting this test.
Step 1: Make a slushy
Fill container with crushed ice
Use ice that is as finely crushed as possible. The smaller the pieces, the more complete the contact between ice and water.
Add water
Pour in approximately 20% additional tap water. Do not worry if it overflows — the important thing is to keep the ice.
Fill all gaps
Ensure all gaps between ice pieces are filled with water. The ice-water interface is exactly 0°C / 32°F — this is the reference point you are testing against.
Target consistency: crushed ice with gaps filled by water.
Step 2: Agitate the sensor continuously
Insert the sensor
Place the WizzTemp sensor into the slushy.
Agitate vigorously
Continually and vigorously move the sensor — like mixing a cup of tea. Move it up and down and around.
Keep moving for 2–3 minutes
After 2–3 minutes, check the reading on the display, but do not stop moving the sensor.
Never stop during the test
Continuous agitation is required for the entire duration of the test. If you stop, the test becomes invalid.
Move the sensor continuously, up and down and around.
Why agitation matters
A stationary probe forms a warmer meltwater layer around itself and reads high. Insufficient agitation is the most common reason the test appears to fail on a healthy probe. If your reading is above the pass threshold, agitate more vigorously and try again before suspecting the sensor.
Expected results
| Reading | Result | Action |
|---|---|---|
0.25°C / 32.45°F or lower | Pass | Sensor is accurate. Exact threshold depends on water impurities. |
Above 0.25°C / 32.45°F | Fail — reading high | 1. Confirm vigorous agitation and fresh ice. 2. Then suspect the probe. |
Below −0.16°C / 31.71°F | Fail — impossibly low | Faulty probe or internal loom. Replace WizzTemp sensor. |
A passing reading during the slushy test.
For more accurate testing
Use deionized water instead of tap water. Without dissolved impurities, the freezing point is closer to exactly 0°C, giving a tighter pass/fail band.
If the test fails
- Repeat the test properly — fresh slushy, fresh ice, vigorous agitation. Most "failures" are actually insufficient agitation.
- Inspect the internal loom for damage or corrosion.
- Change the WizzTemp sensor.
See Ident C in Troubleshooting by Symptom for full diagnostic steps.
Why this matters for carbonation
Carbonation volumes are calculated from temperature. A probe that reads warm causes systematic under-carbonation — the FizzWizz thinks the beer is warmer than it is and calculates less CO₂ than needed. See Carbonation & Brite Pressure for the full chain of cause and effect.