# DHTT22 zero values

**URL:** <https://discourse.nodered.org/t/dhtt22-zero-values/7465>\
**Category:** General\
**Created:** [1 February 2019 09:55 UTC](https://discourse.nodered.org/t/dhtt22-zero-values/7465 "2019-02-01T09:55:09Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![lowcbk](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@lowcbk](https://discourse.nodered.org/u/lowcbk)\
**Post date:** [1 February 2019 09:55 UTC](https://discourse.nodered.org/t/dhtt22-zero-values/7465/1 "2019-02-01T09:55:09Z")

</div>

Have been using node-red-contrib-dht-sensor with DHT22 sensor showing zero values in temperature and humidity :  
(object  
\_msgid: "2bea0790.4d4168"  
topic: "rpi-dht22"  
payload: "0.00"  
humidity: "0.00"  
isValid: false  
errors: 4  
sensorid: "dht22" }.

Anyone has any idea what went wrong? I'm using the Physical Pin Rev.2 with pin 15. All other grounded + power(3.3) are placed correctly. Much Appreciated

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [1 February 2019 09:59 UTC](https://discourse.nodered.org/t/dhtt22-zero-values/7465/2 "2019-02-01T09:59:55Z")

</div>

Not sure about the node since I've never used it. However, I have used DHT22's in the past - they are not much better than the DHT11's and will occasionally give back a rubbish answer. As the `isValid` flag is false, that suggests that the result was rubbish but that the node author decided to make the values zero in such a case - not a good choice in my opinion, they should be something obviously wrong like -99 or, even better, `null`.

* * *

By the way, the DHT 11/22 are rubbish because they are not only terribly inaccurate to begin with but also the sensor drifts over time.

I recently was putting together another sensor platform for the house and decided to put a DHT22 amd a SI7021/HTU21D on the same platform (ESP8266 based), here are the current readings (the DHT22 is the top reading):

![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/c/cfb833da9cfa310a374c6eced91dcf76e89cf14f.png)

As you can see, there is a very significant difference between them. When I tested this platform along-side some of my existing ones just to make sure that I didn't have a duff sensor, the SI7021 gave readings consistent with the other sensors which were either other SI7021's or BME280's.

---

<div class="post-metadata">

**Author:** ![lowcbk](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@lowcbk](https://discourse.nodered.org/u/lowcbk)\
**Post date:** [1 February 2019 10:38 UTC](https://discourse.nodered.org/t/dhtt22-zero-values/7465/3 "2019-02-01T10:38:54Z")

</div>

> [@TotallyInformation](#):
>
> SI7021

Wow! Thanks for the feedback! I would give SI7021 a try. Incidentally DHT22 was working fine until a damage to the sensor due to incorrect power. After that I tried to use a new DHT22 but these zero errors started appearing. I checked the Pins on the Pi and are fine.