Power calculation

[owensca19]

I'm getting data from the GEM and saving it to an influxdb with btmon.
How are amps and watts calculated?
Looking at the data for channel 3 I have .24 amps and 30.2 watts at 121.2 volts
I would expect 29.088 watts. Why is it 30.2?

Here's my config and data

Code: Select all

[source]
ip_read = true
device_type = gem
ip_host = 172.28.0.17
ip_port = 8000
ip_mode = client
include_current = true
reverse_polarity = true
[influxdb]
influxdb_out = true
influxdb_host = localhost
influxdb_port = 8086
influxdb_db_schema = ecmread
influxdb_upload_period = 30
influxdb_mode = col
influxdb_username = *****
influxdb_password = *****
influxdb_database = ecmread
influxdb_measurement = energy

Code: Select all

1610636662000000000 ch10_a XXX155 0
1610636662000000000 ch10_w XXX155 -0
1610636662000000000 ch11_a XXX155 0
1610636662000000000 ch11_w XXX155 -0
1610636662000000000 ch12_a XXX155 0
1610636662000000000 ch12_w XXX155 -0
1610636662000000000 ch13_a XXX155 0
1610636662000000000 ch13_w XXX155 -0
1610636662000000000 ch14_a XXX155 0
1610636662000000000 ch14_w XXX155 -0
1610636662000000000 ch15_a XXX155 0
1610636662000000000 ch15_w XXX155 0.2
1610636662000000000 ch16_a XXX155 0
1610636662000000000 ch16_w XXX155 -0
1610636662000000000 ch17_a XXX155 0
1610636662000000000 ch17_w XXX155 -0
1610636662000000000 ch18_a XXX155 0
1610636662000000000 ch18_w XXX155 -0
1610636662000000000 ch19_a XXX155 0
1610636662000000000 ch19_w XXX155 -0
1610636662000000000 ch1_a  XXX155 0
1610636662000000000 ch1_w  XXX155 -0
1610636662000000000 ch20_a XXX155 0
1610636662000000000 ch20_w XXX155 -0
1610636662000000000 ch21_a XXX155 1.5
1610636662000000000 ch21_w XXX155 142.76666666666668
1610636662000000000 ch22_a XXX155 0.16
1610636662000000000 ch22_w XXX155 13.066666666666666
1610636662000000000 ch23_a XXX155 0.3
1610636662000000000 ch23_w XXX155 24
1610636662000000000 ch24_a XXX155 0.2
1610636662000000000 ch24_w XXX155 14
1610636662000000000 ch25_a XXX155 1.3
1610636662000000000 ch25_w XXX155 136.8
1610636662000000000 ch26_a XXX155 3.68
1610636662000000000 ch26_w XXX155 359.06666666666666
1610636662000000000 ch27_a XXX155 0
1610636662000000000 ch27_w XXX155 2
1610636662000000000 ch28_a XXX155 0
1610636662000000000 ch28_w XXX155 -0
1610636662000000000 ch29_a XXX155 0
1610636662000000000 ch29_w XXX155 -0
1610636662000000000 ch2_a  XXX155 0
1610636662000000000 ch2_w  XXX155 -0
1610636662000000000 ch30_a XXX155 0
1610636662000000000 ch30_w XXX155 -0
1610636662000000000 ch31_a XXX155 0
1610636662000000000 ch31_w XXX155 -0
1610636662000000000 ch32_a XXX155 0
1610636662000000000 ch32_w XXX155 -0
1610636662000000000 ch3_a  XXX155 0.24
1610636662000000000 ch3_w  XXX155 30.2
1610636662000000000 ch4_a  XXX155 0
1610636662000000000 ch4_w  XXX155 -0
1610636662000000000 ch5_a  XXX155 0.1
1610636662000000000 ch5_w  XXX155 7.2
1610636662000000000 ch6_a  XXX155 0
1610636662000000000 ch6_w  XXX155 -0
1610636662000000000 ch7_a  XXX155 0
1610636662000000000 ch7_w  XXX155 -0
1610636662000000000 ch8_a  XXX155 0
1610636662000000000 ch8_w  XXX155 0.5333333333333333
1610636662000000000 ch9_a  XXX155 0
1610636662000000000 ch9_w  XXX155 -0
1610636662000000000 volts  XXX155 121.2

[ben]

I'm getting data from the GEM and saving it to an influxdb with btmon.
How are amps and watts calculated?
Looking at the data for channel 3 I have .24 amps and 30.2 watts at 121.2 volts
I would expect 29.088 watts. Why is it 30.2?

Here's my config and data

Is this being monitored with a Micro-40?

Error is likely when you go below 1A. +-1W is very good given how low the amperage is.

[owensca19]

I'm getting data from the GEM and saving it to an influxdb with btmon.
How are amps and watts calculated?
Looking at the data for channel 3 I have .24 amps and 30.2 watts at 121.2 volts
I would expect 29.088 watts. Why is it 30.2?

Here's my config and data

Is this being monitored with a Micro-40?

Error is likely when you go below 1A. +-1W is very good given how low the amperage is.

I'm using the Micro-80
The error gets larger with higher amps, channel 26 recorded 3.68 amp and 359.066 watts but should be 446.016 amps

I also get the same readings when saving to mysql.
Which value would be the most accurate for calculating Kwh, the amps or the watts?

[ben]

I'm getting data from the GEM and saving it to an influxdb with btmon.
How are amps and watts calculated?
Looking at the data for channel 3 I have .24 amps and 30.2 watts at 121.2 volts
I would expect 29.088 watts. Why is it 30.2?

Here's my config and data

Is this being monitored with a Micro-40?

Error is likely when you go below 1A. +-1W is very good given how low the amperage is.

I'm using the Micro-80
The error gets larger with higher amps, channel 26 recorded 3.68 amp and 359.066 watts but should be 446.016 amps

I also get the same readings when saving to mysql.
Which value would be the most accurate for calculating Kwh, the amps or the watts?

VA won't be accurate at all due to power factor. What are you monitoring with that channel?

359W could be right as around 80% of VA is pretty common due to power factor.

Do you have any outlets being monitored? If so, try plugging in a purely resistive load like a old-school lightbulb (60W), hair dryer, toaster, etc. VA should be within 1% of Watts in that case.

[owensca19]

Is this being monitored with a Micro-40?

Error is likely when you go below 1A. +-1W is very good given how low the amperage is.

I'm using the Micro-80
The error gets larger with higher amps, channel 26 recorded 3.68 amp and 359.066 watts but should be 446.016 amps

I also get the same readings when saving to mysql.
Which value would be the most accurate for calculating Kwh, the amps or the watts?

VA won't be accurate at all due to power factor. What are you monitoring with that channel?

359W could be right as around 80% of VA is pretty common due to power factor.

Do you have any outlets being monitored? If so, try plugging in a purely resistive load like a old-school lightbulb (60W), hair dryer, toaster, etc. VA should be within 1% of Watts in that case.

Thanks for the help Ben. Using the hair dryer did indeed put the VA within the 1%

[ben]

Thanks for the help Ben. Using the hair dryer did indeed put the VA within the 1%

NP. If you have any circuits that tend to be lower amperage, you can try reducing the CT Type by 1 if it's reading too high on average (or increasing it by 1 if it's reading too low).