Sonoff Mini S1 & S2

[regeo]

I have a SONOFF mini R2 and I am playing arround with it. Firstly I know that according to the manual you must not connect live terminals to S1 and S2.

With my Multimeter I can read that the voltage between S1 & S2 is 3.3Volt DC.

The voltage between L & N is 230 Volts AC, the Live wire is the L.

Now, with my multimeter set to Volts AC, measuring the voltage accross S1 & N and s2 & N it measures 227-233 volts.

However, what drives me crazy are the probes in my multimeter.

RED probe in Neutral and Black (COM) probe in S1 shows 227 volts

RED probe in S1 and Black (COM) probe in Neutral show 0 volts

How is this possible?

EDIT: Sorry, I should have post this thread in the "Outside UK forum", please be so kind to move it.

GREECE

 

[FrodoOne]

RED probe in Neutral and Black (COM) probe in S1 shows 227 volts

RED probe in S1 and Black (COM) probe in Neutral show 0 volts

How is this possible?

Does it matter as long as the device works?
S1 and S2 are used as a "control" (as shown in the diagrams which you did not post)
(https://sonoff.tech/wp-content/uploads/2021/03/说明书-MINIR2-V1.1-20210305.pdf )

These are the source of an "Extra Low Voltage" control signal.
You "know that according to the manual you must not connect live terminals to S1 and S2.",
So, why are you doing it, even via a "high impedance" multimeter (Probably Digital)?

High impedance (Digital) multimeters can give strange mis-readings, resulting from very small (inconsequential) "leakage" voltages.

 

[regeo]

You "know that according to the manual you must not connect live terminals to S1 and S2.",
So, why are you doing it, even via a "high impedance" multimeter (Probably Digital)?

Firstly, thank you for your time to respond.

To be honest, I didn't realize I was doing this wrong just by measuring the potential difference (as you said "high impedance" multimeter. So, it's pointless even to refer those terminals.

Would there be a chance for a device (not essential the specific one), to be damaged by referring various terminals with a high impedance multimeter? Let's say you do not have a circuit diagram and you must do your testing/measurements to find out.

 

[oldbutnotdead]

First answer- there are probably one or more diodes in that device, if your DMM is a cheap one it may not be able to tell the difference between full wave and half wave AC.
Second answer- with the DMM set to read voltage, low odds you'll do any damage. If it was set to read impedance or current then yes you definitely can cause damage.
Third answer - an anonymous black box with no circuit diagram, you'd have the lid off and investigate first- looking for any manufacturers reference markings then straight onto Google or Bing to try and acquire info that way.
Fourth answer- you have successfully determined that those control lines S1 (and S2) are at significant voltage referenced to ground, even though the potential between them is at a logic level (3.3v). This is very common with modern mass-produced electronics.

 

[SpecialK]

A shelly 1 will take a mains voltage switched input.