# Telling if an input of 0 is being sent

**URL:** https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162
**Category:** General
**Created:** [8 August 2018 18:38 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162 "2018-08-08T18:38:08Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![acestu](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/acestu/32/90408_2.png) [@acestu](https://discourse.nodered.org/u/acestu)
#### Post date: [8 August 2018 18:38 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162/1 "2018-08-08T18:38:08Z")

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Hi,

I have several inputs from mqtt sensors that feed gauges, in between I have a timeout node that sends 0 to the gauge if there is no input within a 20 minute period so that I can see that something is wrong, I need a node that can tell if a zero is sent so that I can send an email to alert me of the problem, I have looked through the flows library but if you don't know what your looking for it can be a minefield, if anyone could suggest something I would be grateful.

thanks  
Stuart

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### Author: ![davidcgu](https://avatars.discourse-cdn.com/v4/letter/d/e8c25b/32.png) [@davidcgu](https://discourse.nodered.org/u/davidcgu)
#### Post date: [8 August 2018 18:39 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162/2 "2018-08-08T18:39:12Z")

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Check the trigger node

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### Author: ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)
#### Post date: [8 August 2018 18:43 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162/3 "2018-08-08T18:43:51Z")

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what about the switch node? Just test for a 0

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### Author: ![ukmoose](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ukmoose/32/13_2.png) [@ukmoose](https://discourse.nodered.org/u/ukmoose)
#### Post date: [8 August 2018 18:44 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162/4 "2018-08-08T18:44:15Z")

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If I'm understanding you, can't you do that with the already-included switch node?

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### Author: ![acestu](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/acestu/32/90408_2.png) [@acestu](https://discourse.nodered.org/u/acestu)
#### Post date: [8 August 2018 18:48 UTC](https://discourse.nodered.org/t/telling-if-an-input-of-0-is-being-sent/2162/5 "2018-08-08T18:48:58Z")

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Thanks guys the switch node works fine == 0

cheers  
Stuart