September 24, 20223 yr Hi! I have bought a Eastron SDM72DR MID energy meter. I have been trying to find information about the pulse output but failed. Does anyone know if it is sink or source? As I understand the S0 interface could be either one. I was planning to connect 5V -> 20k resistor to S0+ and S0- to ground. Best regards Björn
September 25, 20223 yr 10 hours ago, Bjornw78 said: Hi! I have bought a Eastron SDM72DR MID energy meter. I have been trying to find information about the pulse output but failed. Does anyone know if it is sink or source? As I understand the S0 interface could be either one. I was planning to connect 5V -> 20k resistor to S0+ and S0- to ground. Best regards Björn @Bjornw78 hi, typically the output is a opto-coupled open-collector transistor output, so your proposed arrangement is ok for that. In practice however youll have to increase noise immunity by lowering that 20k all the way down to 470 ohms in order to sink at least 10 milliamps thru the transistor. And then you need to put that 470R pullup on the far end of the cable to ensure you sinking thru the cable. Then you must also have a shielded cable with the shield tied to ov. These two prerequisites are needed to make sure that noise or transient does not cause phantom energy pulses. Edited September 25, 20223 yr by BritishRacingGreen Misspelling
September 25, 20223 yr 10 hours ago, Bjornw78 said: Does anyone know if it is sink or source? Because the transistor is not internally wetted, its unconnected to wetting voltage, its not applicable. EDIT : of course this is based on assumption that the transistor is uncomitted. But all the meters i have worked with is optically isolated, floating output. Which means if you measure voltage between S0 and S1 on your energy meter, it will be 0v. Edited September 25, 20223 yr by BritishRacingGreen
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