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MSR38-D/DP safety relay circuit

MSR38-D/DP safety relay circuit

(OP)
I'm trying to understand MSR38-D/DP. The safety relays I am familiar with has redundant chains; a (+) channel and (-) channel. Looking at the diagram, MSR38-D/DP seems to have S11 & S12 as one chain, and S21 & S22 as the other chain. So, as the picture below shows, since the chain circuits are completed, I should get 24V when I put my meter leads across S11 & S21, right? But when I did that, I get no voltage, but the relay has two green LEDs on for the two output channels.

What confuses me more is the seconds diagram; how can S21 be connected to the reset (S34), and S22 connected to the (+) chain?

RE: MSR38-D/DP safety relay circuit

Good morning

" since the chain circuits are completed, I should get 24V when I put my meter leads across S11 & S21, right? "
No, those are both outputs to guards, Estop, ect.

" , but the relay has two green LEDs on for the two output channels "

The green led's indicate K1, K2 are closed.

" What confuses me more is the seconds diagram; how can S21 be connected to the reset (S34), and S22 connected to the (+) chain? "

The first diagram is for machine's with Reset buttons, if guard is opened it must be closed and a reset button must be pushed to clear error.

The second diagram is auto reset, the guard simply needs to be closed and error is cleared.

Chuck

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