# How to calculate negative modbus value?

**URL:** https://discourse.nodered.org/t/how-to-calculate-negative-modbus-value/36283
**Category:** General
**Created:** [21 November 2020 10:49 UTC](https://discourse.nodered.org/t/how-to-calculate-negative-modbus-value/36283 "2020-11-21T10:49:59Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![syma33](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/syma33/32/30665_2.png) [@syma33](https://discourse.nodered.org/u/syma33)
#### Post date: [21 November 2020 12:01 UTC](https://discourse.nodered.org/t/how-to-calculate-negative-modbus-value/36283/4 "2020-11-21T12:01:48Z")

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> [@Colin](#):
>
> Does the x value represent ohms or what?  
> What x values are you getting and what values are X and Y max and min?  
> What formula are you using at the moment and are the values correct for positive values?

x = analogue signal but might not be ohm value, the FTX does not tell..  
for positive values, i just read it straight off the modbus 🙂

But i think i found my answer here... will try this solution soon.

> [@MODBUS 16bit SIGNED INTEGER](https://discourse.nodered.org/t/modbus-16bit-signed-integer/25362/4):
>

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