chander Posted July 20 Share Posted July 20 1pm connected to single light switch switch is off energy usage shows no energy usage voltage shows no voltage this is correct turn light switch on energy usage shows upward trend on device graph voltage shows 120V (USA) correct turn light switch off energy usage shows zero accumulation = zero energy usage BUT voltage still shows 120V monitored for 12 hours, same result no energy in graph but voltage graph shows 120V WHY? Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 20 Members Share Posted July 20 (edited) In Shelly 1PM, voltage measurement is situated before the switch. Thus, voltage indication should be steadily - independent from the state of the switch. By the way: Power in alternating current systems is defined as Voltage by Current by Power Factor. Hence, no current flowing at a time gives no power… Edited July 20 by thgoebel Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
chander Posted July 20 Author Share Posted July 20 if I only want to monitor voltage, only need to record the exact time the light switch is on or off should I use a shelly EM? if yes, can I wire the outlet power and neutral directly into the shelly EM like I did with the shelly 1PM? I do not want to use the shelly EM in the electrical panel and monitor an entire circuit, only want to monitor a single light switch. or is there a better shelly product to monitor voltage for a single light switch? Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
tvbshelly Posted July 20 Share Posted July 20 (edited) A Shelly EM uses a current clamp = current transformer (CT) to measure the wire and is also connected to L of the same phase and N. The CT naturally takes up space, but the advantage is that the load current does not have to flow through the Shelly. Alternatively, you can use a Shelly PM Mini Gen3, which is really small, can only measure (1 channel 16 A), but is inline, i.e. the measured current also flows through the Shelly. However, I believe that a PM Mini Gen3 is not suitable, because if it is installed after the switch and gets no power, the device is off and you get no status at all. Edited July 20 by tvbshelly Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
chander Posted July 22 Author Share Posted July 22 question If the PM Mini Gen3 is powered after the switch then every time the switch gets turned on, the Mini must reconnect to the wifi every time? Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
tvbshelly Posted July 22 Share Posted July 22 Yes, the Mini is switched on with the switch, starts and then connects to the Wifi every time. I assume that this is probably not the best solution for your use case. Quote Translate Revert translation? English (American) Finnish French German Italian Portuguese (European) Spanish Link to comment Share on other sites More sharing options...
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