# Cerbo gx resistance tank level not correct?

**URL:** <https://community.victronenergy.com/t/cerbo-gx-resistance-tank-level-not-correct/10027>\
**Category:** DIY\
**Tags:** display, expert, marine, cerbo\_gx\
**Created:** [2 November 2024 13:48 UTC](https://community.victronenergy.com/t/cerbo-gx-resistance-tank-level-not-correct/10027 "2024-11-02T13:48:14Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![pamaca](https://avatars.discourse-cdn.com/v4/letter/p/da6949/32.png) [@pamaca](https://community.victronenergy.com/u/pamaca)\
**Post date:** [2 November 2024 13:48 UTC](https://community.victronenergy.com/t/cerbo-gx-resistance-tank-level-not-correct/10027/1 "2024-11-02T13:48:14Z")

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Hi,  
I’ve been trying to make sense of my diesel tank level.  
I have a US tank probe 240 - 30 ohm, the cerbo shows that this is reading 127.6 ohms and makes that out to be 53%  
I would have expected that to be nearer 40%  
Thoughts please

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<div class="post-metadata">

**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\
**Post date:** [2 November 2024 18:59 UTC](https://community.victronenergy.com/t/cerbo-gx-resistance-tank-level-not-correct/10027/2 "2024-11-02T18:59:23Z")

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Empty 240 Ohm  
Full 30 Ohm

Total range 240 - 30 = 210 Ohm  
current level range = 240 - 127.6 = 112.4 Ohm  
Reading = 112.4 / 210 = 53.5%. QED.

A simple thought experiment, 127.6 Ohm is closer to 30 Ohm (full) than 240 Ohm (empty) so it should be above 50%.

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<div class="post-metadata">

**Author:** ![pamaca](https://avatars.discourse-cdn.com/v4/letter/p/da6949/32.png) [@pamaca](https://community.victronenergy.com/u/pamaca)\
**Post date:** [2 November 2024 20:12 UTC](https://community.victronenergy.com/t/cerbo-gx-resistance-tank-level-not-correct/10027/3 "2024-11-02T20:12:34Z")

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Hi,

Yep, your maths is spot on.

I was working from a spreadsheet of real values that I measured from an identical probe.

The probe has 12 resistance steps, but the values for the first 2 steps from the bottom decrease by 50 ohms each, then the rest of the steps are around 12 ohms.

I think this is what is throwing out the reading, when I dip the tank it’s around 35 to 40% full.

If I had a high resistance joint then I would expect it to show less.

More investigation required, or bin it and get a more linear probe

Cheers