---
title: Error message Measured Density VC and Measured NC are less than or equal to zero.
description: Error message Measured Density VC and Measured NC are less than or equal to zero.
---

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# Error message Measured Density VC and Measured NC are less than or equal to zero.

## Error message Measured Density VC and Measured NC are less than or equal to zero.

When performing a calibration an error "Message measured density VC and measured density NC are less than or equal to zero" may appear. 

This error message appears when previous calibrations were performed with a dirty U-tube. Overtime, the zero point keeps moving, then when the U-tube is finally cleaned, the values fall below zero.

To resolve the error, 

1. Clean the U-tube
2. Perform a factory restore
3. Perform a new 2-point calibration 
     1. If you continue to see the error message during the calibration, keep accepting them, allowing the calibration to complete, you may see the error multiple times until the calibration is completed.

 

 

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