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I am working with a DC relay thats contacts are rated at up to 10 amps at 600v.

I am aware relays also tend to have a minimum switching current, however none is listed for this relay and this seems common that it isnt. At how low of voltage/amperage is that worth considering? Is there any guidance.

This relays going to feed a digital input on an IO system. Its wetted at 48V DC which should be plenty to not have any minimum issues. However it is current limited to 4-8ma and I cant find any guidance on if thats plenty of current or something worth worrying about and speccing a relay meant for lower loads.

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    \$\begingroup\$ Is there a datasheet you can share? Generally, if the contacts aren't designed for low signal levels (gold plated, usually), you do run the risk of contact oxide buildup, which it sounds like you're aware of. As you can see on this datasheet for a 10A relay (te.com/commerce/DocumentDelivery/…), the minimum contact load is 100mA so if your relay is anything similar, you'd be well advised to look for a signal relay. \$\endgroup\$
    – vir
    Commented Jun 3, 2021 at 16:12
  • \$\begingroup\$ So at the link below is the relay. The reason we went with such a heavy duty relay is just based on where it is and the fact its being used to drive some solenoids etc. Just one spare contacts being used to let the DCS know its status. It sounds like given the minimum load is 100ma for something similar that you are right. Just odd bc the dcs vendor has noted 0 issues with contacts like these being picked up se.com/us/en/product/8501XDO40V62Y414/… \$\endgroup\$
    – Robert Ryder
    Commented Jun 3, 2021 at 17:19
  • \$\begingroup\$ If it's not a critical application and you could tolerate and identify an intermittent contact fault in your signal, you could give it a shot. Otherwise, you could use the contact to actuate a signal relay or change to a power relay with auxiliary contacts which are designed for low-current status signalling. \$\endgroup\$
    – vir
    Commented Jun 3, 2021 at 17:33
  • \$\begingroup\$ Do you have any examples of power relays with auxiliary contacts like that? Just like general model lines. \$\endgroup\$
    – Robert Ryder
    Commented Jun 3, 2021 at 17:44
  • \$\begingroup\$ @vir - you should make this an answer. "Dry" contacts are a real problem. \$\endgroup\$
    – Mattman944
    Commented Jun 3, 2021 at 18:59

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For the contact/switch side of the relay, there is no minimum current once the contacts have been actuated.

For the coil side of the relay, there is a minimum current and that needs to be followed according to the datasheet and is usually non-negotiable as this is the required magnetic force to pull the contacts together.

The coil actuates the contacts but only does so with the appropriate current in the coil. Once the contacts have made contact there is a small amount of contact resistance that varies from relay to relay (and is usually listed in the datasheet). If the coil requires 48V and 4mA to be actuated, then you will need to provide that.

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