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The WattNode® Pulse meter is available with Option SSR, which uses a solid-state relay in place of the normal optoisolators. This allows switching AC voltages and higher currents than the optoisolators. The effective “on resistance” is also much lower for the solid-state relay than for the optoisolator, so the SSR more closely approximates a true relay.


  • Maximum pulse frequency: 30 Hz
  • Maximum DC voltage: ±60 Vdc
  • Maximum AC voltage: 40 Vac
  • Maximum switching current: 500 mA
  • On resistance: 1.0 to 2.5 ohms
  • Off state leakage: 1 microamp max
  • Turn on time: 1.8 ms typical, 5.0 ms maximum
  • Turn off time: 0.5 ms typical, 2.0 ms maximum
  • Maximum Recommended Pulse Frequency: 30 Hz


The switching speed is much slower for the SSR than for the normal optoisolator outputs, so the maximum recommended pulse frequency is 30 Hz. Also, the off-state leakage current is higher than the optoisolators, although still very low at one microamp maximum.

See Also

Keywords: opto-isolator, opto-coupler, photo-MOS, photo-MOSFET, optoMOS, opto-MOS, opto-MOSFET