IRT 4020:
- Color: Pastel Green
- Small measuring head cover instead of storage
- 1 button for switching on and fairs
- Only 1 memory: last measurement is displayed automatically on power up.
- Only automatic shutdown (after 60 sec.)
IRT 4520:
- Colour: white / blue
- Storage box (rather a somewhat chunky tray) with space for storage caps. No extra probe cover.
- Add. Save button on the front; is the same on-off switch (measuring button as with 4020 on back).
- 8 presets: the last 8 temperature measurements are available, the last measurement is displayed automatically on power up.
Press 3 seconds on the I / O switch: manually switched off -.
Note 1:. Both models come including 20 one-caps + 2 AA batteries and have 2 years warranty..
. Note 2: It does not seem to act 4520 to the successor at the IRT, as both models are listed in Amazon since 2004.