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emonth2 blog

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Glyn Hudson 2016-11-30 00:17:51 +00:00
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readme.md
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@ -23,7 +23,7 @@ Data from the emonTH is transmitted via wireless RF (433MHz) to an emonPi / emon
### Related Blog Posts
- [Introducing emonTH V2](https://blog.openenergymonitor.org/2016/11/introducing emonth-v2)
- [Introducing emonTH V2](http://blog.openenergymonitor.org/2016/09/emonth2/)
- [Optical Pulse Counting with emonTH](https://blog.openenergymonitor.org/2015/09/optical-pulse-counting-with-emonth/)
- [emonTH V1 Prototype](https://blog.openenergymonitor.org/2013/06/emonth-prototype/)

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sensor/readme.md
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| Metric | [HTU21D](https://octopart.com/htu21d-measurement+specialties-30374934) |[Si72021](https://octopart.com/si7021-a20-im-silicon+labs-52675246)| DHT22 | DHT22 vs HTU21D Difference| [BME280](https://octopart.com/bme280-bosch-52931981) |
| ------------- | ------------- |------------- | ------------- | ------------- | ------------- |
| Cost in 1k off | £1.42 (July16) |£2.15| £4.57 (July16) | 3.2 times cheaper (£3.15 less!) | £3.07 |
| Vcc | 2.1v - 3.6V | 1.9V - 3.6V | 3.3-6V | | 1.71 V - 3.6V |
| Humidity accuracy | ±2% RH | ±2% RH | ±2%RH | n/a | ±3%RH |
| Humidity Range | 0-100% RH | 0-100% RH | 0-100% RH | n/a| 0-100% RH |
| Temperature accuracy | ±0.3°C | ±0.4°C| ±0.5°C | 40% more accurate | ±0.5 - ±1.0 |
| Temperature Range | -40°C +125°C | -40°C +125°C | -40°C +80°C | 56% more accurate | -40°C +80°C |
| Sleep Current | 0.02uA | 0.06uA | 15uA | 750 times less power | 0.1uA - 0.3uA |
| Measurement Current | 0.045mA | 0.09 mA | 0.5mA | 11 times less power | 0.714mA - 0.350mA |
| Measurement time | 0.01s - 0.0026s | 0.01s - 0.0026s | 2s | 200 times faster | 0.013s |
| Energy consumed per sample | 1.5uJ | 2.97uJ | 3300uJ | 2000 times less power | |
| Time sampling per day* | 14.4s || 2800s | | |
| Time sleeping per day* | 86386s || 83600s | | |
| Energy consumed per day* | 7.8mJ [1] || 8700mJ [2] | 1115 times less energy per day! | |
| ------------- | --------|------------- | ------------- | ------------- | ------------- |
| Cost in 1k off | £2.15| £4.57 (July16) | 3.2 times cheaper (£3.15 less!) | £3.07 |
| Vcc | 1.9V - 3.6V | 3.3-6V | | 1.71 V - 3.6V |
| Humidity accuracy | ±2% RH | ±2%RH | n/a | ±3%RH |
| Humidity Range | 0-100% RH | 0-100% RH | n/a| 0-100% RH |
| Temperature accuracy | ±0.4°C| ±0.5°C | 40% more accurate | ±0.5 - ±1.0 |
| Temperature Range | -40°C +125°C | -40°C +80°C | 56% more accurate | -40°C +80°C |
| Sleep Current | 0| 0.06uA | 15uA | 750 times less power | 0.1uA - 0.3uA |
| Measurement Current | 0. 0.09 mA | 0.5mA | 11 times less power | 0.714mA - 0.350mA |
| Measurement time | 0.01s | 0.01s - 0.0026s | 2s | 200 times faster | 0.013s |
| Energy consumed per sample| 2.97uJ | 3300uJ | 2000 times less power | |
| Time sampling per day* || 2800s | | |
| Time sleeping per day* | | 83600s | | |
| Energy consumed per day* || 8700mJ [2] | 1115 times less energy per day! | |
```
energy consumed (joule, J) = potential difference (volt, V) × charge (coulomb, C)
charge (coulomb, C) = current (ampere, A) × time (second, s)
energy consumed (joule, J) = potential difference (volt, V) × current (ampere, A) × time (second, s)
energy consumed (joule, J) = potential difference (volt, V) × charge (coulomb, C)
charge (coulomb, C) = current (ampere, A) × time (second, s)
energy consumed (joule, J) = potential difference (volt, V) × current (ampere, A) × time (second, s)
```
## Energy consumed per day*
Energy consumed per day = energy consumed per sample + energy consumed while sleeping.
Energy consumed per day = energy consumed per sample + energy consumed while sleeping.
- **HTU21D:** (1400 * 0.0015mJ) + (3.3V * 0.00002mA * 86386 ) = 2.1mJ + 5.7mJ = 7.8mJ [1]
- **DHT22:** (1400 * 3.3mJ) + (3.3V * 0.015mA * 83600) = 4.6mJ + 4.1J = 8.7J = 8700mJ [2]